Thesis - faculty.ait.ac.th - Asian Institute of Technology
Thesis - faculty.ait.ac.th - Asian Institute of Technology
Thesis - faculty.ait.ac.th - Asian Institute of Technology
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APPLICATION OF MEMBRANE BIOREACTOR SYSTEMS FOR<br />
LANDFILL LEACHATE TREATMENT<br />
i<br />
by<br />
Boonchai Wichitsa<strong>th</strong>ian<br />
A dissertation submitted in partial fulfillment <strong>of</strong> <strong>th</strong>e requirements for <strong>th</strong>e<br />
degree <strong>of</strong> Doctor <strong>of</strong> Technical Science<br />
Examination Committee: Pr<strong>of</strong>. C. Visvana<strong>th</strong>an (Chairman)<br />
Dr. Preeda Parkpian<br />
Dr. Josef Trankler<br />
Pr<strong>of</strong>. A<strong>th</strong>apol Noomhorm<br />
External Examiner: Pr<strong>of</strong>. F.W. Gün<strong>th</strong>ert<br />
Institut für Wasserwesen<br />
Fakultät für Bauingenieur- und Vermessungswesen<br />
Universität der Bundeswehr München<br />
Neubiberg, Germany<br />
Nationality: Thai<br />
Previous Degrees: B<strong>ac</strong>helor <strong>of</strong> Industrial Chemistry<br />
King Mongkut’s <strong>Institute</strong> <strong>of</strong> <strong>Technology</strong> Thonburi<br />
Bangkok, Thailand<br />
Master <strong>of</strong> Environmental <strong>Technology</strong><br />
King Mongkut’s <strong>Institute</strong> <strong>of</strong> <strong>Technology</strong> Thonburi<br />
Bangkok, Thailand<br />
Scholarship Donor: Royal Thai Government<br />
<strong>Asian</strong> <strong>Institute</strong> <strong>of</strong> <strong>Technology</strong><br />
School <strong>of</strong> Environment, Resources and Development<br />
Thailand<br />
August 2004
Acknowledgements<br />
I would like to deeply express my pr<strong>of</strong>ound gratitude to his advisor, Pr<strong>of</strong>. C.<br />
Visvana<strong>th</strong>an for kindly giving his stimulating ideas, valuable guidance, numerous<br />
constructive suggestions and encouragement <strong>th</strong>rough his study at AIT. The au<strong>th</strong>or also<br />
would like to <strong>th</strong>ank Dr. Preeda Parkpian, Dr. Josef Trankler, Dr. David A. Luketina, Dr.<br />
Lee Seung-Hwan, and Pr<strong>of</strong>. A<strong>th</strong>apol Noomhorm for <strong>th</strong>eir valuable comments, critical ideas<br />
and serving as members <strong>of</strong> examination committee.<br />
I am greatly indebted to Pr<strong>of</strong>. F.W. Gun<strong>th</strong>ert for kindly <strong>ac</strong>cepting to serve as<br />
External Examiner. His valuable advice, guidance and pr<strong>of</strong>essional comments are highly<br />
appreciated.<br />
I gratefully <strong>ac</strong>knowledge to Royal Thai Government for <strong>th</strong>e financial support.<br />
I am very grateful to Ms. Sindhuja Sankaran and Ms. Loshnee Nair for providing<br />
comments and helping <strong>th</strong>roughout my study at AIT.<br />
I sincerely would like to <strong>th</strong>ank all staffs and my lab colleagues in <strong>th</strong>e<br />
Environmental Engineering Program for friendship, help, and moral support, which<br />
contributed in various ways to <strong>th</strong>e completion <strong>of</strong> <strong>th</strong>is dissertation.<br />
Sincere gratitude is expressed to <strong>th</strong>e Pa<strong>th</strong>um<strong>th</strong>ani municipality and Ram-indra<br />
transfer station <strong>of</strong>fice, Thailand, for <strong>th</strong>e useful information and assistance on <strong>th</strong>e le<strong>ac</strong>hate<br />
and sample collection.<br />
Finally, I would like to express my deepest gratitude and dedicate <strong>th</strong>is research<br />
work to my parents, all family members and special friends, whose love, assisted me<br />
<strong>th</strong>rough difficult times and contributed to <strong>th</strong>e success <strong>of</strong> <strong>th</strong>is study.<br />
ii
Abstr<strong>ac</strong>t<br />
Landfill le<strong>ac</strong>hate is a complex wastewater wi<strong>th</strong> considerable variation in bo<strong>th</strong> quality<br />
and quantity. The composition and concentration <strong>of</strong> pollutants are influenced by <strong>th</strong>e types<br />
<strong>of</strong> waste deposited, hydrogeological f<strong>ac</strong>tors, and more significantly by <strong>th</strong>e age <strong>of</strong> <strong>th</strong>e<br />
landfill site. In general, le<strong>ac</strong>hate is highly contaminated wi<strong>th</strong> organic contaminants<br />
measured as chemical oxygen demand (COD) and biochemical oxygen demand (BOD),<br />
and also wi<strong>th</strong> high ammonium nitrogen concentration. Biological processes have been<br />
found ineffective for le<strong>ac</strong>hate from relatively old landfill. In le<strong>ac</strong>hate containing high<br />
concentrations <strong>of</strong> organic and nitrogen compounds such cases result in possible serious<br />
environmental problems near <strong>th</strong>e landfill site.<br />
This research was undertaken to investigate <strong>th</strong>e performance <strong>of</strong> a membrane<br />
biore<strong>ac</strong>tor (MBR) using mixed yeast culture (YMBR) and mixed b<strong>ac</strong>teria culture (BMBR)<br />
in treating raw le<strong>ac</strong>hate containing high organic and nitrogen concentrations. The<br />
inhibition effects <strong>of</strong> ammonium nitrogen and lead on yeast and b<strong>ac</strong>teria cultures were<br />
determined by measuring <strong>th</strong>e oxygen uptake rate (OUR) using <strong>th</strong>e respirometric me<strong>th</strong>od.<br />
Fur<strong>th</strong>ermore, for bo<strong>th</strong> YMBR and BMBR, treating <strong>th</strong>e stripped le<strong>ac</strong>hate, <strong>th</strong>ey were<br />
assessed <strong>th</strong>e treatment efficiency to compare <strong>th</strong>e results wi<strong>th</strong> <strong>th</strong>ose treating <strong>th</strong>e raw<br />
le<strong>ac</strong>hate.<br />
The inhibition experiment revealed <strong>th</strong>at a b<strong>ac</strong>teria culture was very sensitive to<br />
ammonium nitrogen when it was compared to a yeast culture. Also <strong>th</strong>e values <strong>of</strong> biokinetic<br />
coefficients showed <strong>th</strong>at <strong>th</strong>e specific grow<strong>th</strong> rate (µ) in b<strong>ac</strong>teria system was influenced. At<br />
ammonium concentration <strong>of</strong> 2,000 mg/L, <strong>th</strong>e response <strong>of</strong> OUR inhibition in a b<strong>ac</strong>teria<br />
system was approximately 37% whereas it was around 6% in a yeast system. Fur<strong>th</strong>ermore,<br />
bo<strong>th</strong> yeast and b<strong>ac</strong>teria cultures were also sensitive to lead.<br />
In a MBR, treating raw le<strong>ac</strong>hate, <strong>th</strong>e COD removal rate for BMBR was slightly<br />
lower <strong>th</strong>an <strong>th</strong>e YMBR for varied hydraulic retention time (HRT) at high volumetric<br />
loading rate. The average COD removal efficiency in BMBR was 62±2% while in YMBR<br />
was 65±2%. The YMBR could obtain higher COD removal rate at higher volumetric<br />
loading rate <strong>th</strong>an <strong>th</strong>e BMBR. This indicated <strong>th</strong>at <strong>th</strong>e yeast system can treat le<strong>ac</strong>hate<br />
containing high organic and nitrogen concentrations. The average TKN removal efficiency<br />
for bo<strong>th</strong> BMBR and YMBR systems was from 14-25% and 19-29%, respectively. The<br />
nitrite and nitrate concentrations (NO2 - and NO3 - ) were found to be very low.<br />
The comparative evaluation <strong>of</strong> treatment performance <strong>of</strong> MBR, treating stripped<br />
le<strong>ac</strong>hate, was examined. The COD removal <strong>of</strong> bo<strong>th</strong> BMBR and YMBR was above 70% at<br />
HRT 16 h and 24 h. As a result, <strong>th</strong>e pretreatment wi<strong>th</strong> ammonia stripping prior to BMBR<br />
showed more significant improvement in terms <strong>of</strong> COD removal when it was compared to<br />
YMBR. This could be confirmed <strong>th</strong>at <strong>th</strong>e trend <strong>of</strong> inhibition effect on b<strong>ac</strong>teria was<br />
dependent upon <strong>th</strong>e ammonium nitrogen concentration. The range <strong>of</strong> BOD concentration<br />
<strong>of</strong> effluents from bo<strong>th</strong> YMBR and BMBR, treating <strong>th</strong>e stripped le<strong>ac</strong>hate was from 30-55<br />
mg/L. This level followed <strong>th</strong>e present effluent standard. Al<strong>th</strong>ough BOD could be reduced<br />
to lower values wi<strong>th</strong> <strong>th</strong>ese me<strong>th</strong>ods, <strong>th</strong>e treated le<strong>ac</strong>hate still contained a large quantity <strong>of</strong><br />
refr<strong>ac</strong>tory organic compounds. This might be due to <strong>th</strong>e contribution <strong>of</strong> <strong>th</strong>e slowly<br />
biodegradable organics and non-biodegradable organics contained in <strong>th</strong>e le<strong>ac</strong>hate.<br />
Therefore, <strong>th</strong>ey should be fur<strong>th</strong>er treated in a post treatment for elevating <strong>th</strong>e final effluent<br />
to meet <strong>th</strong>e present effluent standard or even increasing <strong>th</strong>e biodegradable organics.<br />
iii
Under <strong>th</strong>e same operating conditions, <strong>th</strong>e YMBR could run under transmembrane<br />
pressure (TMP) 1.3-2.5 times lower <strong>th</strong>an <strong>th</strong>e BMBR wi<strong>th</strong> <strong>th</strong>e significantly reduced<br />
membrane fouling rate. This might be due to <strong>th</strong>e soluble extr<strong>ac</strong>ellular polymeric substances<br />
(soluble EPS). Hence, yeast system could enhance membrane performance and had <strong>th</strong>e<br />
potential to improve <strong>th</strong>e treatment system due to reduction <strong>of</strong> operational problems. In<br />
addition, b<strong>ac</strong>teria sludge showed a better dewatering quality compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast<br />
sludge.<br />
iv
Table <strong>of</strong> Contents<br />
Chapter Title Page<br />
Title Page i<br />
Acknowledgements ii<br />
Abstr<strong>ac</strong>t iii<br />
Table <strong>of</strong> Contents v<br />
List <strong>of</strong> Tables viii<br />
List <strong>of</strong> Figures x<br />
List <strong>of</strong> Abbreviations xii<br />
1 Introduction 1<br />
1.1 B<strong>ac</strong>kground 1<br />
1.2 Objectives <strong>of</strong> <strong>th</strong>e Study 3<br />
1.3 Scope <strong>of</strong> <strong>th</strong>e Study 4<br />
2 Literature Review 5<br />
2.1 Introduction 5<br />
2.2 Solid Waste Management Pr<strong>ac</strong>tices 6<br />
2.3 Municipal Solid Waste Landfill 7<br />
2.4 Municipal Solid Waste Landfill Le<strong>ac</strong>hate 7<br />
2.5 Le<strong>ac</strong>hate Composition and Char<strong>ac</strong>teristics 8<br />
2.6 Molecular Weight Distribution in Landfill Le<strong>ac</strong>hate 11<br />
2.7 F<strong>ac</strong>tors Affecting Le<strong>ac</strong>hate Composition 12<br />
2.7.1 Seasonal Variation 13<br />
2.7.2 Landfill Age 14<br />
2.7.3 Composition <strong>of</strong> <strong>th</strong>e Waste Dumped 16<br />
2.7.4 Geological Char<strong>ac</strong>teristic 16<br />
2.7.5 Filling Technique 16<br />
2.8 Le<strong>ac</strong>hate Treatment 17<br />
2.8.1 Biological Treatment Processes 18<br />
2.8.2 Physical Treatment 24<br />
2.8.3 Chemical Treatment 30<br />
2.8.4 Natural Le<strong>ac</strong>hate Treatment Systems 33<br />
2.8.5 Co-Treatment wi<strong>th</strong> Municipal Wastewater 35<br />
2.9 Combined Treatment F<strong>ac</strong>ility 36<br />
2.9.1 Biological Treatment and Reverse Osmosis 36<br />
2.9.2 Micr<strong>of</strong>iltration and Reverse Osmosis 37<br />
2.9.3 Denitrification-Nitrification/Ultrafiltration and Reverse Osmosis 38<br />
2.9.4 MBR-UV and Ozone-Reverse Osmosis 39<br />
2.10 Microbial Toxicity 39<br />
2.11 Membrane Biore<strong>ac</strong>tors 41<br />
2.11.1 Membrane Configuration 42<br />
2.11.2 Application <strong>of</strong> Membrane Biore<strong>ac</strong>tors 44<br />
2.11.3 Sludge Char<strong>ac</strong>teristics 45<br />
2.12 Yeasts 49<br />
2.12.1 Introduction 49<br />
2.12.2 Applications <strong>of</strong> Yeasts for Wastewater Treatment 49<br />
v
2.13 Rationale for <strong>th</strong>e Study and Proposed Treatment Sequence 52<br />
2.13.1 Le<strong>ac</strong>hate Char<strong>ac</strong>teristic 52<br />
2.13.2 Need for Ammonia Stripping 52<br />
2.13.3 Need for Membrane Biore<strong>ac</strong>tors 53<br />
3 Me<strong>th</strong>odology 54<br />
3.1 Introduction 54<br />
3.2 Le<strong>ac</strong>hate Char<strong>ac</strong>terization 54<br />
3.3 Seed Study 55<br />
3.3.1 Yeast and B<strong>ac</strong>terial Sludge 55<br />
3.3.2 Acclimatization 56<br />
3.4 Toxicity Studies 56<br />
3.4.1 Ammonia Toxicity 57<br />
3.4.2 Lead Toxicity 58<br />
3.5 Ammonia Stripping 58<br />
3.6 Membrane Biore<strong>ac</strong>tor 59<br />
3.6.1 Membrane Resistance Measurement 59<br />
3.6.2 Experimental Set-up 60<br />
3.6.3 Parametric Studies 62<br />
3.6.4 Molecular Weight Distribution 62<br />
3.6.5 Sludge Char<strong>ac</strong>terization 64<br />
3.7 Ammonia Stripping Coupled Membrane Biore<strong>ac</strong>tor 64<br />
3.8 Analytical Me<strong>th</strong>ods 65<br />
4 Results and Discussion 67<br />
4.1 Simulation <strong>of</strong> Le<strong>ac</strong>hate Char<strong>ac</strong>teristic for Treatment <strong>of</strong><br />
Middle Aged Le<strong>ac</strong>hate 67<br />
4.2 Biokinetic Studies 68<br />
4.2.1 Acclimatization <strong>of</strong> Mixed Yeast and B<strong>ac</strong>terial Sludge 68<br />
4.2.2 Kinetics <strong>of</strong> Yeast and B<strong>ac</strong>terial Grow<strong>th</strong> 72<br />
4.2.3 Toxicity Studies 75<br />
4.3 Application <strong>of</strong> Yeast and B<strong>ac</strong>teria Based Membrane Biore<strong>ac</strong>tors<br />
in Le<strong>ac</strong>hate Treatment 80<br />
4.3.1 Initial Membrane Resistance 81<br />
4.3.2 Optimization <strong>of</strong> HRT in Terms <strong>of</strong> Membrane Biore<strong>ac</strong>tor<br />
Treatment Efficiency 82<br />
4.3.3 Membrane Fouling and Membrane Resistance 89<br />
4.4 Application <strong>of</strong> Yeast and B<strong>ac</strong>teria Based Membrane Biore<strong>ac</strong>tors<br />
in Ammonia Stripped Le<strong>ac</strong>hate Treatment 91<br />
4.4.1 Ammonia Stripping Studies 91<br />
4.4.2 Membrane Resistance and Membrane Cleaning 95<br />
4.4.3 Performance <strong>of</strong> Ammonia Stripping Coupled Membrane<br />
Biore<strong>ac</strong>tor Process 97<br />
4.5 O<strong>th</strong>er Studies 106<br />
4.5.1 Biodegradability <strong>of</strong> <strong>th</strong>e Le<strong>ac</strong>hate 106<br />
4.5.2 Molecular Weight Cut-<strong>of</strong>f 110<br />
4.5.3 Sludge Properties 115<br />
4.5.4 EPS Formation 116<br />
4.5.5 Conductivity and TDS 117<br />
vi
4.5.6 Cost Analysis for Operation 117<br />
5 Conclusions and Recommendations 119<br />
5.1 Conclusions 119<br />
5.2 Recommendations for Future Work 121<br />
References 123<br />
Appendix A: Pictures <strong>of</strong> Experiments 141<br />
Appendix B: Le<strong>ac</strong>hate Char<strong>ac</strong>teristics and Experimental<br />
Data <strong>of</strong> Acclimation 145<br />
Appendix C: Experimental Data <strong>of</strong> Biokinetic Study and<br />
Toxicity Study 149<br />
Appendix D: Membrane Resistance Studies 155<br />
Appendix E: MBR wi<strong>th</strong>out Ammonia Stripping 163<br />
Appendix F: Ammonia Stripping Studies 171<br />
Appendix G: MBR wi<strong>th</strong> Ammonia Stripping 174<br />
Appendix H: O<strong>th</strong>er Studies 179<br />
vii
List <strong>of</strong> Tables<br />
Tables Title Page<br />
2.1 Le<strong>ac</strong>hate Char<strong>ac</strong>teristic in Acidogenic and Me<strong>th</strong>anogenic Phase<br />
in a Landfill 8<br />
2.2 Comparison <strong>of</strong> Le<strong>ac</strong>hate Char<strong>ac</strong>teristics <strong>of</strong> Landfills Surveyed in<br />
Asia, Europe and America 10<br />
2.3 Relation between Landfill Age, Le<strong>ac</strong>hate Char<strong>ac</strong>teristics and Treatments 11<br />
2.4 Classification <strong>of</strong> Types <strong>of</strong> Substances Using Molecular Weight Cut<strong>of</strong>f 12<br />
2.5 Variation <strong>of</strong> COD, BOD & BOD/COD wi<strong>th</strong> Increasing Landfill Ages 15<br />
2.6 Nitrogen Concentrations from Various Sources 15<br />
2.7 Nitrogen Concentration Ranges in <strong>th</strong>e Le<strong>ac</strong>hate for Landfill Stabilization 15<br />
2.8 Summary <strong>of</strong> Biokinetic Coefficient <strong>of</strong> Activated Sludge Process for<br />
Landfill Le<strong>ac</strong>hate Treatment 19<br />
2.9 Operational and Environmental Conditions for Nitrification-<br />
Denitrification Processes 23<br />
2.10 Treatment Efficiencies <strong>of</strong> Different Aerobic Biological Treatment<br />
Systems 25<br />
2.11 Treatment Efficiencies <strong>of</strong> Different Anaerobic Biological Treatment<br />
Systems 26<br />
2.12 Membrane Processes 28<br />
2.13 Removal Efficiency <strong>of</strong> Moderate to High Concentrations <strong>of</strong> Pollutants<br />
Using Nan<strong>of</strong>iltration, Ultrafiltration and Reverse Osmosis 28<br />
2.14 Typical Reverse Osmosis Plant Performance for Le<strong>ac</strong>hate Purification,<br />
Germany 30<br />
2.15 Treatment Efficiencies <strong>of</strong> Different Physico-chemical Treatment Systems 34<br />
2.16 Typical Le<strong>ac</strong>hate Composition at E<strong>ac</strong>h Stage <strong>of</strong> Le<strong>ac</strong>hate Treatment Plant 39<br />
2.17 Inhibitory Effect <strong>of</strong> Various Toxicants 41<br />
2.18 Advantages and Disadvantages <strong>of</strong> Membrane Biore<strong>ac</strong>tors 43<br />
2.19 Operating Conditions <strong>of</strong> Membrane Biore<strong>ac</strong>tor Process for Treatment<br />
<strong>of</strong> Different Kinds <strong>of</strong> Wastewater 46<br />
2.20 Operating Conditions <strong>of</strong> Yeast System Compared wi<strong>th</strong> Activated<br />
Sludge Process 51<br />
2.21 Performance <strong>of</strong> Yeast Based Treatment System in Dried Food Products<br />
and Marine Product Industry 51<br />
3.1 Composition <strong>of</strong> Simulated Le<strong>ac</strong>hate 55<br />
3.2 Operating Conditions for Yeast and B<strong>ac</strong>teria Acclimatization 56<br />
3.3 Operating Conditions for Yeast and B<strong>ac</strong>teria Mixtures in Respirometer 57<br />
3.4 Description <strong>of</strong> <strong>th</strong>e Chemical Cleaning 60<br />
3.5 Technical Parameters <strong>of</strong> <strong>th</strong>e Experimental Plant 60<br />
3.6 Experimental Operating Conditions <strong>of</strong> YMBR and BMBR Systems 62<br />
3.7 Char<strong>ac</strong>teristics <strong>of</strong> Ultrafiltration Membrane 64<br />
3.8 Parameters and Their Analytical Me<strong>th</strong>ods 66<br />
4.1 Compositions <strong>of</strong> Le<strong>ac</strong>hate Simulated from Le<strong>ac</strong>hates Obtained from<br />
Pa<strong>th</strong>um-<strong>th</strong>ani Landfill Site (PS) and Ram-Indra Transfer Station (RIS) 67<br />
4.2 Biokinetic Coefficients <strong>of</strong> Yeast and B<strong>ac</strong>teria Sludge for <strong>th</strong>e Le<strong>ac</strong>hates 74<br />
4.3 Effect <strong>of</strong> Free Ammonia Concentration on Yield Coefficient and <strong>th</strong>e<br />
Specific Grow<strong>th</strong> Rate <strong>of</strong> <strong>th</strong>e B<strong>ac</strong>terial Sludge 76<br />
viii
4.4 Effect <strong>of</strong> Free Ammonia Concentration on Yield Coefficient and <strong>th</strong>e<br />
Specific Grow<strong>th</strong> Rate <strong>of</strong> <strong>th</strong>e Yeast Sludge 77<br />
4.5 Substrate Utilization by <strong>th</strong>e Yeast and B<strong>ac</strong>terial Sludge 79<br />
4.6 COD Removal Efficiency in YMBR System at Different HRT 85<br />
4.7 COD Removal Efficiency in BMBR System at Different HRT 86<br />
4.8 TKN Removal Efficiency in YMBR System 88<br />
4.9 TKN Removal Efficiency in BMBR System 88<br />
4.10 Membrane Cleaning Frequency in <strong>th</strong>e MBR Systems 90<br />
4.11 Membrane Resistance in <strong>th</strong>e MBR Systems 90<br />
4.12 Variation in Ammonia Removal Efficiency 94<br />
4.13 Determination <strong>of</strong> Membrane Resistance <strong>of</strong> Membrane Module after<br />
Clogging in BMBR system (A = 0.42 m2; Pore Size = 0.1 µm) 96<br />
4.14 Contribution <strong>of</strong> BOD at 5, 10 and 15 Days to <strong>th</strong>e Total 20 Days BOD 108<br />
4.15 Sludge Properties in <strong>th</strong>e YMBR and BMBR Systems 115<br />
4.16 MLSS and MLVSS Concentrations in Yeast and B<strong>ac</strong>teria Re<strong>ac</strong>tors 116<br />
4.17 Bound EPS Concentration in <strong>th</strong>e YMBR and BMBR Systems 116<br />
4.18 Soluble EPS Concentration in <strong>th</strong>e YMBR and BMBR Systems 116<br />
4.19 Conductivity and TDS Concentrations in Le<strong>ac</strong>hate and Effluents 117<br />
4.20 Cost <strong>of</strong> Chemical Used for pH Adjustment 118<br />
4.21 Total Chemical Cost Requirement for E<strong>ac</strong>h Treatment System 118<br />
ix
List <strong>of</strong> Figures<br />
Figures Title Page<br />
2.1 Schematic Representation <strong>of</strong> a Typical Engineered Landfill 6<br />
2.2 Changes in Significant Parameters during Different Phases <strong>of</strong><br />
Landfill Stabilization 7<br />
2.3 Variation in Significant Pollutant Ratios wi<strong>th</strong> Increase in Age<br />
<strong>of</strong> <strong>th</strong>e Landfill 9<br />
2.4 Water Movements in <strong>th</strong>e Landfill 13<br />
2.5 Le<strong>ac</strong>hate Productions and Rainfall Variation wi<strong>th</strong> Time 14<br />
2.6 Treatment <strong>of</strong> Landfill Le<strong>ac</strong>ahte wi<strong>th</strong> Two Stage Reverse Osmosis 29<br />
2.7 Schematic Diagram <strong>of</strong> Biological Treatment and Reverse Osmosis<br />
for Le<strong>ac</strong>hate Treatment 37<br />
2.8 Schematic Diagram <strong>of</strong> Micr<strong>of</strong>iltration/Reverse Osmosis for<br />
Le<strong>ac</strong>hate Treatment 38<br />
2.9 Schematic Diagram <strong>of</strong> Denitrification-Nitrification/UF and<br />
Reverse Osmosis for Le<strong>ac</strong>hate Treatment 38<br />
2.10 Schematic Diagrams <strong>of</strong> (a) External Recirculation MBR and<br />
(b) Submerged MBR System 42<br />
3.1 Flowchart Showing Different Stages <strong>of</strong> Experimental Study 54<br />
3.2 Diagram Illustrating <strong>th</strong>e Enrichment Procedure 55<br />
3.3 Respirometer 57<br />
3.4 Experiments Conducted to Optimize Ammonia Stripping 59<br />
3.5 Schematic Diagrams <strong>of</strong> Membrane Biore<strong>ac</strong>tor wi<strong>th</strong> and wi<strong>th</strong>out<br />
Ammonia Stripping 61<br />
3.6 Me<strong>th</strong>odology for Performing Molecular Weight Cut-<strong>of</strong>f Distribution 63<br />
3.7 Flowchart Showing Ammonia Stripping Coupled MBR Process 65<br />
4.1 Variation in F/M and COD Removal Efficiency in Yeast Sludge 69<br />
4.2 Variation in F/M and COD Removal Efficiency in B<strong>ac</strong>terial Sludge 69<br />
4.3 Increase in Biomass during Acclimatization <strong>of</strong> <strong>th</strong>e B<strong>ac</strong>terial Sludge 70<br />
4.4 Increase in Biomass during Acclimatization <strong>of</strong> <strong>th</strong>e Yeast Sludge 71<br />
4.5 Predominantly Spherical and Egg-shaped Yeasts wi<strong>th</strong> Budding in<br />
<strong>th</strong>e Yeast Re<strong>ac</strong>tor (x1500) 71<br />
4.6 B<strong>ac</strong>teria Cells in <strong>th</strong>e Mixed B<strong>ac</strong>teria Sludge: a) Gram Negative and<br />
b) Gram Positive (x1500) 72<br />
4.7 Specific Grow<strong>th</strong> Rate <strong>of</strong> Mixed B<strong>ac</strong>teria Sludge wi<strong>th</strong> Increasing<br />
Substrate Concentration 72<br />
4.8 Specific Grow<strong>th</strong> Rate <strong>of</strong> Mixed Yeast Sludge wi<strong>th</strong> Increasing<br />
Substrate Concentration 72<br />
4.9 Inhibition <strong>of</strong> <strong>th</strong>e Yeast and B<strong>ac</strong>terial Culture wi<strong>th</strong> Increasing<br />
Ammonium Chloride Concentration 77<br />
4.10 Inhibitory Effect <strong>of</strong> Lead in B<strong>ac</strong>terial Sludge 79<br />
4.11 Inhibition Effect <strong>of</strong> Lead in Yeast Sludge 80<br />
4.12 Variation in Transmembrane Pressure wi<strong>th</strong> Permeate Flux (a) YMBR<br />
and (b) BMBR 81<br />
4.13 Variation in Organic Load wi<strong>th</strong> HRT 83<br />
4.14 Variation in MLSS in <strong>th</strong>e MBR Systems 83<br />
4.15 Variation in pH in <strong>th</strong>e MBR Systems 84<br />
x
4.16 COD Concentration in <strong>th</strong>e Influent and Effluent in <strong>th</strong>e BMBR and<br />
YMBR at Different HRT 84<br />
4.17 COD Removal Efficiency in <strong>th</strong>e BMBR and YMBR at Different HRT 85<br />
4.18 Variations in COD Removal Rate as a Function <strong>of</strong> F/M Ratio 86<br />
4.19 TKN Removal Efficiency in <strong>th</strong>e YMBR and BMBR wi<strong>th</strong> HRT 87<br />
4.20 Cleaning <strong>of</strong> membranes in <strong>th</strong>e YMBR and BMBR system in<br />
relation to TMP 90<br />
4.21 Variation in <strong>th</strong>e Ammonia Removal Efficiency wi<strong>th</strong> pH 93<br />
4.22 Ammonia Removal Efficiency wi<strong>th</strong> Varying Velocity Gradient and pH 93<br />
4.23 Trans-membrane Pressure Variation in MBR Process for Ammonia<br />
Stripped Le<strong>ac</strong>hate Treatment 96<br />
4.24 Variation in COD at 16 and 24 h HRT 98<br />
4.25 Variation in MLSS at 16 and 24 h HRT 98<br />
4.26 COD Removal wi<strong>th</strong> and wi<strong>th</strong>out Ammonia Stripping at 16 and 24 h HRT 99<br />
4.27 Expected and Actual Improvement in COD Removal wi<strong>th</strong> Ammonia<br />
Stripping in <strong>th</strong>e YMBR and BMBR Systems 100<br />
4.28 BOD in <strong>th</strong>e BMBR and YMBR Effluent at 16 h HRT 101<br />
4.29 BOD in <strong>th</strong>e BMBR and YMBR Effluent at 24 h HRT 101<br />
4.30 BOD Removal Efficiency in <strong>th</strong>e BMBR and YMBR Systems 102<br />
4.31 BOD/COD <strong>of</strong> <strong>th</strong>e BMBR and YMBR Effluent 102<br />
4.32 Influent and Effluent Nitrogen Content in BMBR at (a) 16 h HRT and<br />
(b) 24 h HRT 103<br />
4.33 Influent and Effluent Nitrogen Content in YMBR at (a) 16 h HRT and<br />
(b) 24 h HRT 104<br />
4.34 Overall TKN Removal in BMBR and YMBR wi<strong>th</strong> and wi<strong>th</strong>out<br />
Ammonia Stripping 105<br />
4.35 TKN Removal in MBR Process at 16 and 24 h HRT 106<br />
4.36 Change <strong>of</strong> OUR at Different Time Period for Le<strong>ac</strong>hate Sample 107<br />
4.37 20 Days BOD <strong>of</strong> <strong>th</strong>e Raw Le<strong>ac</strong>hate and Stripped Le<strong>ac</strong>hate 109<br />
4.38 20 Days BOD <strong>of</strong> <strong>th</strong>e YMBR and BMBR Effluents 109<br />
4.39 Molecular Weight Cut-<strong>of</strong>f <strong>of</strong> Raw Le<strong>ac</strong>hate, Stripped Le<strong>ac</strong>hate,<br />
B<strong>ac</strong>terial and Yeast Effluents 111<br />
4.40 Percent Contribution <strong>of</strong> Various Molecular Weight Compounds to<br />
<strong>th</strong>e Total COD 111<br />
4.41 Molecular Weight Cut-<strong>of</strong>f <strong>of</strong> Le<strong>ac</strong>hate (a) COD (mg/L) (b) COD (%) 113<br />
4.42 Molecular Weight Cut-<strong>of</strong>f <strong>of</strong> Le<strong>ac</strong>hate (a) BOD (mg/L) (b) BOD (%) 114<br />
xi
List <strong>of</strong> Abbreviations<br />
AAS Atomic Absorption Spectrophotometer<br />
AnSBR Anaerobic Sequencing Batch Re<strong>ac</strong>tors<br />
AOX Adsorbable Organic Halogens<br />
AS Activated Sludge<br />
BACFB Biological Activated Carbon Fluidized Bed Process<br />
BOD Biochemical Oxygen Demand<br />
BMBR B<strong>ac</strong>terial Membrane Biore<strong>ac</strong>tors<br />
C Carbon<br />
cm Centimeter<br />
COD Chemical Oxygen Demand<br />
CST Capillary Suction Time<br />
d Day<br />
Da Daltons<br />
DO Dissolved Oxygen<br />
DOC Dissolved Organic Carbon<br />
DSVI Diluted Sludge Volume Index<br />
EMBR Extr<strong>ac</strong>tive Membrane Biore<strong>ac</strong>tor<br />
EPS Extr<strong>ac</strong>ellular Polymeric Substances<br />
F/M Food/Microorganism ratio<br />
FS Fixed Solids<br />
g Gram<br />
G Mean velocity gradient<br />
GAC Granular Activated Carbon<br />
h Hour<br />
HRT Hydraulic Retention Time<br />
J Permeate flux<br />
k Substrate removal rate<br />
kDa Kilo Daltons<br />
kg Kilogram<br />
kPa Kilo Pascal<br />
kWh Kilowatt-hour<br />
kd Endogenous decay coefficient<br />
ke Mean re<strong>ac</strong>tion rate coefficient<br />
Ks Half-velocity constant<br />
L Liter<br />
m Meter<br />
m 2 Square meter<br />
m 3 Cubic meter<br />
m 3 /d Cubic meter per day<br />
mg/L Milligram per liter<br />
min Minute<br />
MAACFB Microorganism Att<strong>ac</strong>hed Activated Carbon Fluidized Bed Process<br />
MABR Membrane Aeration Biore<strong>ac</strong>tors<br />
MBR Membrane Biore<strong>ac</strong>tor<br />
MF Micr<strong>of</strong>iltration<br />
MLSS Mixed Liquor Suspended Solids<br />
MLVSS Mixed Liquor Volatile Suspended Solids<br />
MW Molecular Weight<br />
xii
MWCO Molecular Weight Cut-<strong>of</strong>f<br />
MWW Municipal Wastewater<br />
N Nitrogen<br />
NF Nan<strong>of</strong>iltration<br />
NH3-N Ammonia Nitrogen<br />
NH4-N Ammonium Nitrogen<br />
NO2-N Nitrite Nitrogen<br />
NO3-N Nitrate Nitrogen<br />
NOM Natural Organic Matter<br />
OLR Organic Loading Rate<br />
OUR Oxygen Uptake Rate<br />
P Phosphorus<br />
Pa Pascal<br />
PAC Powder Activated Carbon<br />
PS Pa<strong>th</strong>um<strong>th</strong>ani Landfill Site<br />
R Filtration resistance<br />
Rc Resistance due to cake layer<br />
Rm Intrinsic resistance<br />
Rn Resistance due to irreversible fouling<br />
Rt Total resistance<br />
RBC Rotating Biological Cont<strong>ac</strong>tor<br />
RIS Ram-indra Transfer Station<br />
RO Reverse Osmosis<br />
rpm Rotations per minute<br />
s Seconds<br />
So/Xo Substrate/Biomass ratio<br />
Ss Readily biodegradable organics<br />
SBR Sequencing Batch Re<strong>ac</strong>tor<br />
SCBP Suspended Carrier Bi<strong>of</strong>ilm Process<br />
SD Standard Deviation<br />
SRT Sludge Retention Time<br />
SS Suspended Solids<br />
SVI Sludge Volume Index<br />
T Temperature<br />
TDS Total Dissolved Solid<br />
TOC Total Organic Carbon<br />
TKN Total Kjedahl Nitrogen<br />
TMP Transmembrane Pressure<br />
TS Total Solids<br />
TVS Total Volatile Solids<br />
U Substrate Utilization Rate<br />
UASB Upflow Anaerobic Sludge Blanket<br />
UF Ultrafiltration<br />
USB/AF Upflow Hybrid Sludge Bed/Fixed Bed Anaerobic<br />
UV Ultraviolet<br />
VFA Volatile Fatty Acid<br />
VLR Volumetric Loading Rate<br />
VS Volatile Solids<br />
VSS Volatile Suspended Solids<br />
Xs Slowly biodegradable organics<br />
xiii
Y Yield coefficient<br />
YMBR Yeast Membrane Biore<strong>ac</strong>tor<br />
Өc Solid retention time<br />
o C Degree Celsius<br />
∆P Transmembrane Ppessure<br />
µ Vicosity<br />
µm Micrometer<br />
µmax Maximum specific grow<strong>th</strong> rate<br />
µS/cm Microsiemens per centimeter<br />
xiv
1.1 B<strong>ac</strong>kground<br />
Chapter 1<br />
Introduction<br />
Rapid industrialization and urbanization has resulted in an immense environmental<br />
degradation. Population grow<strong>th</strong> and poor environmental management pr<strong>ac</strong>tices have led to<br />
deterioration <strong>of</strong> environmental quality in most <strong>of</strong> <strong>th</strong>e developing countries. The<br />
composition <strong>of</strong> <strong>th</strong>e domestic refuse has radically changed in char<strong>ac</strong>ter over <strong>th</strong>e last fifty<br />
years, due to <strong>th</strong>e rise <strong>of</strong> an affluent society. In recent years, solid waste management has<br />
gained focus in many countries. Source reduction, reuse and recycling <strong>of</strong> waste,<br />
composting, incineration and landfill disposal are few <strong>of</strong> <strong>th</strong>e solid waste management<br />
appro<strong>ac</strong>hes pr<strong>ac</strong>ticed in different countries. The suitability <strong>of</strong> <strong>th</strong>ese appro<strong>ac</strong>hes differs from<br />
pl<strong>ac</strong>e to pl<strong>ac</strong>e. Municipal solid waste disposal in <strong>th</strong>e landfill is <strong>th</strong>e most common, cheap<br />
and easiest municipal solid waste management pr<strong>ac</strong>tice followed <strong>th</strong>roughout <strong>th</strong>e world.<br />
However, landfill requires a close environmental engineering surveillance in its design and<br />
operation as it is likely to generate le<strong>ac</strong>hate which would potentially contaminate nearby<br />
groundwater and surf<strong>ac</strong>e water. Wi<strong>th</strong> <strong>th</strong>e changing nature <strong>of</strong> domestic refuse composition<br />
over <strong>th</strong>e years, <strong>th</strong>e proportion <strong>of</strong> refuse available for decomposition has greatly increased<br />
and <strong>th</strong>us <strong>th</strong>e organic streng<strong>th</strong> <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate has increased, resulting in its greater potential<br />
to pollute water. A need exist to focus on <strong>th</strong>e environmental problems concerned wi<strong>th</strong><br />
domestic landfill disposal to protect <strong>th</strong>e environment and prevent adverse heal<strong>th</strong> affects.<br />
Surf<strong>ac</strong>e water <strong>th</strong>at percolates <strong>th</strong>rough <strong>th</strong>e landfill and le<strong>ac</strong>hes out organic and<br />
inorganic constituents from <strong>th</strong>e solid waste is termed le<strong>ac</strong>hate. Landfill le<strong>ac</strong>hate production<br />
starts at <strong>th</strong>e early stages <strong>of</strong> <strong>th</strong>e landfill and continues several decades even after landfill<br />
closure. Landfill le<strong>ac</strong>hate is mainly generated by <strong>th</strong>e infiltrating water, which passes<br />
<strong>th</strong>rough <strong>th</strong>e solid waste fill and f<strong>ac</strong>ilitates transfer <strong>of</strong> contaminants from solid phase to<br />
liquid phase. Due to <strong>th</strong>e inhomogeneous nature <strong>of</strong> <strong>th</strong>e waste and because <strong>of</strong> <strong>th</strong>e differing<br />
comp<strong>ac</strong>tion densities <strong>th</strong>at will be encountered, water will be able to percolate <strong>th</strong>rough and<br />
appear as le<strong>ac</strong>hate at <strong>th</strong>e base <strong>of</strong> <strong>th</strong>e site. If no remedial measures are taken to prevent<br />
continual inputs <strong>of</strong> water to <strong>th</strong>e wastes, <strong>th</strong>is could pose adverse environmental imp<strong>ac</strong>ts.<br />
Landfill le<strong>ac</strong>hate is high streng<strong>th</strong> wastewater which contains high concentrations <strong>of</strong><br />
organic matter and ammonium nitrogen. There is a fluctuation in <strong>th</strong>e composition <strong>of</strong><br />
organic, inorganic and heavy metal components in <strong>th</strong>e le<strong>ac</strong>hate making <strong>th</strong>em more difficult<br />
to be dealt wi<strong>th</strong>. The composition depends on <strong>th</strong>e landfill age, <strong>th</strong>e quality and quantity <strong>of</strong><br />
solid waste, <strong>th</strong>e biological and chemical processes occurring in <strong>th</strong>e landfill, and <strong>th</strong>e amount<br />
<strong>of</strong> precipitation and percolation. When <strong>th</strong>e le<strong>ac</strong>hate containing high streng<strong>th</strong> organic matter<br />
and ammonia is discharged wi<strong>th</strong>out treatment, it can stimulate algae grow<strong>th</strong> <strong>th</strong>rough<br />
nutrient enrichment, deplete dissolved oxygen, and cause toxic effects in <strong>th</strong>e surrounding<br />
water environment. Landfill design and operation have a major imp<strong>ac</strong>t and influence on <strong>th</strong>e<br />
le<strong>ac</strong>hate generation. This le<strong>ac</strong>hate varies from landfill to landfill and over time and sp<strong>ac</strong>e in<br />
a particular landfill wi<strong>th</strong> fluctuations apparent over short and long-term periods due to<br />
climatic, hydrogeology and waste composition variations (Keenan, et al., 1984). Generally,<br />
le<strong>ac</strong>hate contaminants are measured in terms <strong>of</strong> chemical oxygen demand (COD) and<br />
biological oxygen demand (BOD), halogenated hydrocarbons and heavy metals. In<br />
addition, le<strong>ac</strong>hate usually contains high concentrations <strong>of</strong> inorganic salts - mainly sodium<br />
1
chloride, carbonate and sulfate and is dependent on <strong>th</strong>e waste composition land-filled. An<br />
average fresh domestic refuse le<strong>ac</strong>hate can have a BOD <strong>of</strong> around 15,000 mg/L. When<br />
compared to an average raw sewage BOD <strong>of</strong> 200 mg/L, it can be seen <strong>th</strong>at landfill le<strong>ac</strong>hate<br />
is around 75 times as strong in terms <strong>of</strong> its polluting potential.<br />
Sufficient means have to be evolved to deal wi<strong>th</strong> landfill le<strong>ac</strong>hate so <strong>th</strong>at its imp<strong>ac</strong>t<br />
can be minimized. Le<strong>ac</strong>hate treatment and prevention or minimization <strong>of</strong> le<strong>ac</strong>hate<br />
generation is primarily <strong>th</strong>e two prime options available for landfill le<strong>ac</strong>hate management.<br />
Disposal <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate in <strong>th</strong>e sewer is an attr<strong>ac</strong>tive option, but <strong>th</strong>e variation in <strong>th</strong>e quality<br />
<strong>of</strong> <strong>th</strong>e sewage and le<strong>ac</strong>hate and remoteness <strong>of</strong> <strong>th</strong>e landfill sites make <strong>th</strong>is option difficult<br />
pr<strong>ac</strong>tically. Le<strong>ac</strong>hate treatment has inevitably become a much more widespread<br />
requirement at landfills. It is a technology which has only developed in 1980 in <strong>th</strong>e UK,<br />
but is now advancing rapidly as experience is being gained on full scale landfills<br />
(Robinson, et al., 1992).The main environmental problem experienced at landfills has<br />
resulted from a loss <strong>of</strong> le<strong>ac</strong>hate from <strong>th</strong>e site and <strong>th</strong>e subsequent contamination <strong>of</strong><br />
surrounding land and water. Improvements in landfill engineering has been aimed at<br />
reducing le<strong>ac</strong>hate production, collecting and treating le<strong>ac</strong>hate prior to discharge and<br />
<strong>th</strong>ereby limiting le<strong>ac</strong>hate infiltration to <strong>th</strong>e surrounding soil (Farquhar, 1989). However a<br />
need exists to develop reliable, sustainable options to effectively manage le<strong>ac</strong>hate<br />
generation and treatment. In designing a le<strong>ac</strong>hate treatment scheme, <strong>th</strong>e process must<br />
reflect <strong>th</strong>e possibility <strong>th</strong>at treatment techniques which work well for a young le<strong>ac</strong>hate may<br />
become wholly inadequate as <strong>th</strong>e landfill age increases.<br />
There are difficulties concerned wi<strong>th</strong> <strong>th</strong>e treatment <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate. First, <strong>th</strong>e<br />
variability and streng<strong>th</strong> <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate have important waste treatment application. Second,<br />
<strong>th</strong>e changes encountered from landfill to landfill are such <strong>th</strong>at waste treatment technology<br />
applicable at one site may not be directly transferable to o<strong>th</strong>er location. Third, fluctuations<br />
in <strong>th</strong>e le<strong>ac</strong>hate quality which occur over bo<strong>th</strong> short and long interval must be <strong>ac</strong>counted for<br />
in <strong>th</strong>e treatment design and long interval must be <strong>ac</strong>counted for in <strong>th</strong>e treatment design.<br />
Current treatment pr<strong>ac</strong>tices in developed countries advocate le<strong>ac</strong>hate minimization<br />
by operating landfills as dry as possible; <strong>th</strong>is poses <strong>th</strong>e problem <strong>of</strong> long-term landfill<br />
stabilization. The alternative <strong>of</strong> operating <strong>th</strong>e landfill as wet as possible by le<strong>ac</strong>hate recirculation<br />
does address <strong>th</strong>e problem <strong>of</strong> le<strong>ac</strong>hate treatment by reducing organics. However,<br />
<strong>th</strong>is me<strong>th</strong>od does not prove effective in treating “hard COD” or refr<strong>ac</strong>tory compounds and<br />
nitrogen. Therefore, it does not meet municipal discharge standards. Various biological<br />
treatment me<strong>th</strong>ods have been employed for <strong>th</strong>e treatment <strong>of</strong> le<strong>ac</strong>hate from municipal solid<br />
waste landfill. Extended aeration systems, sequencing batch re<strong>ac</strong>tors and aerated lagoons<br />
can <strong>ac</strong>t as robust, stable and reliable means <strong>of</strong> treating le<strong>ac</strong>hate. These treatment systems<br />
were found to be inefficient for le<strong>ac</strong>hate containing high streng<strong>th</strong> organic substances and<br />
ammonia nitrogen. In addition, <strong>th</strong>e organic loading and pH are significant in influencing<br />
<strong>th</strong>e grow<strong>th</strong> <strong>of</strong> nitrifying b<strong>ac</strong>teria in nitrification process (Aberling, et al., 1992; Bea, et al.,<br />
1997; Kabdasli, et al., 2000). Due to high ammonia concentrations in <strong>th</strong>e le<strong>ac</strong>hate,<br />
ammonia toxicity and sludge properties are affected in <strong>th</strong>e biological treatment systems. A<br />
reed bed treatment system can also be designed to treat effluent by passing it <strong>th</strong>rough <strong>th</strong>e<br />
rhizomes <strong>of</strong> <strong>th</strong>e reed. However, such treatment systems would not deal satisf<strong>ac</strong>torily<br />
because reed bed are poor in removing ammonia. Additionally, ammonium concentration<br />
as high as approximately 1,000 mg/L <strong>of</strong> untreated le<strong>ac</strong>hate feed, might be directly toxic<br />
(Robinson, et al., 1992). The physical treatment systems used for treatment <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate<br />
include <strong>ac</strong>tivated carbon adsorption, filtration, evaporation; etc. These processes are<br />
2
generally unsuccessful in removal <strong>of</strong> organic material from <strong>th</strong>e raw le<strong>ac</strong>hate. The chemical<br />
me<strong>th</strong>ods include coagulation and precipitation and oxidation <strong>of</strong> <strong>th</strong>e organics. The<br />
disadvantage <strong>of</strong> <strong>th</strong>e coagulation and precipitation is <strong>th</strong>at large amounts <strong>of</strong> sludge are<br />
produced which is difficult to manage. Nei<strong>th</strong>er biological nor chemical/physical treatment<br />
separately <strong>ac</strong>hieves high removal efficiency. Physical-chemical treatment is needed to<br />
remove <strong>th</strong>e metals and hydrolyze some <strong>of</strong> <strong>th</strong>e organics whilst biological treatment is<br />
necessary for stabilization and degradation <strong>of</strong> organic matter. Looking into <strong>th</strong>ese aspects,<br />
landfill le<strong>ac</strong>hate treatment requires some advanced treatment technique, to meet <strong>th</strong>e<br />
required effluent standards.<br />
Membrane biore<strong>ac</strong>tor systems are an example <strong>of</strong> an emerging advanced le<strong>ac</strong>hate<br />
treatment technology. Application <strong>of</strong> <strong>th</strong>e membrane coupled <strong>ac</strong>tivated sludge process in<br />
le<strong>ac</strong>hate treatment is very promising because <strong>of</strong> <strong>th</strong>e expected effluent quality. The design<br />
<strong>of</strong> <strong>th</strong>e membrane biore<strong>ac</strong>tor is becoming more affordable and <strong>th</strong>e equipment more reliable.<br />
Membrane biore<strong>ac</strong>tor systems are suspended grow<strong>th</strong> <strong>ac</strong>tivated sludge treatment systems<br />
<strong>th</strong>at rely upon <strong>th</strong>e membrane equipment for liquid/solid separation prior to <strong>th</strong>e discharge <strong>of</strong><br />
<strong>th</strong>e le<strong>ac</strong>hate. Two reasons <strong>th</strong>at exist for <strong>th</strong>e poor removal efficiency <strong>of</strong> <strong>th</strong>e individual<br />
treatment system is <strong>th</strong>e high percentage <strong>of</strong> high molecular weight organic material and<br />
ammonium concentration to be removed and biological inhibition caused by <strong>th</strong>e heavy<br />
metal which may be present in <strong>th</strong>e le<strong>ac</strong>hate.<br />
Sufficient knowledge about <strong>th</strong>e capability and <strong>th</strong>e performance <strong>of</strong> membrane<br />
biore<strong>ac</strong>tors plants for le<strong>ac</strong>hate treatment is yet to be found. Moreover, membrane systems<br />
are <strong>of</strong>ten subjected to clogging and <strong>th</strong>is poses serious problems for operation and<br />
maintenance. In order to reduce <strong>th</strong>e problems <strong>of</strong> frequent membrane clogging, <strong>th</strong>e<br />
application <strong>of</strong> yeast culture to treat wastewater can be considered. The membrane<br />
biore<strong>ac</strong>tor system wi<strong>th</strong> yeast can be employed to treat <strong>th</strong>e wastewater containing high<br />
amount <strong>of</strong> dissolved solids, high concentrations <strong>of</strong> organic matter and o<strong>th</strong>er substances,<br />
which are difficult to treat using conventional biological systems.<br />
Consequently, depending on <strong>th</strong>e char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate, a combination <strong>of</strong><br />
biological and physio-chemical processes can <strong>ac</strong>hieve high removal efficiencies. Thus, <strong>th</strong>e<br />
objective <strong>of</strong> <strong>th</strong>is study is introducing <strong>th</strong>e emerging technology <strong>of</strong> membrane biore<strong>ac</strong>tors<br />
and its role in le<strong>ac</strong>hate treatment. Thereafter, a rationale has been developed for <strong>th</strong>e<br />
treatment <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate produced under tropical conditions <strong>of</strong> Thailand. The experiments<br />
have been conducted in <strong>th</strong>e laboratory to find <strong>th</strong>e performance <strong>of</strong> membrane biore<strong>ac</strong>tor<br />
using yeast culture (YMBR) and b<strong>ac</strong>teria culture (BMBR) and coupled wi<strong>th</strong> ammonia<br />
stripping for removal <strong>of</strong> organic substances from <strong>th</strong>e landfill le<strong>ac</strong>hate. This treatment<br />
system could <strong>ac</strong>t as an innovative appro<strong>ac</strong>h in <strong>th</strong>e future wi<strong>th</strong> regard to <strong>th</strong>e landfill<br />
management pr<strong>ac</strong>tices.<br />
1.2 Objectives <strong>of</strong> <strong>th</strong>e Study<br />
The objectives <strong>of</strong> <strong>th</strong>is study are to investigate <strong>th</strong>e performance <strong>of</strong> membrane<br />
biore<strong>ac</strong>tor using yeast culture and b<strong>ac</strong>teria culture and to examine <strong>th</strong>e prospects <strong>of</strong><br />
applying membrane biore<strong>ac</strong>tor in landfill le<strong>ac</strong>hate treatment. The specific objectives are as<br />
follows:<br />
3
1. To investigate and evaluate <strong>th</strong>e performance <strong>of</strong> membrane biore<strong>ac</strong>tor using yeast<br />
culture (YMBR) and b<strong>ac</strong>teria culture (BMBR) for <strong>th</strong>e treatment <strong>of</strong> landfill le<strong>ac</strong>hate<br />
containing high organic and high ammonia concentrations;<br />
2. To investigate and evaluate <strong>th</strong>e performance <strong>of</strong> ammonia stripping coupled<br />
membrane biore<strong>ac</strong>tor process for <strong>th</strong>e landfill le<strong>ac</strong>hate treatment and to compare <strong>th</strong>e<br />
results wi<strong>th</strong> <strong>th</strong>e treatment performance wi<strong>th</strong>out pre-treatment;<br />
3. To evaluate <strong>th</strong>e respiratory inhibition effects <strong>of</strong> ammonia and lead concentrations on<br />
mixed yeast and mixed b<strong>ac</strong>teria culture;<br />
4. To investigate <strong>th</strong>e potential <strong>of</strong> ammonia stripping for ammonia removal and examine<br />
<strong>th</strong>e f<strong>ac</strong>tors influencing <strong>th</strong>e ammonia removal efficiency;<br />
5. To understand <strong>th</strong>e effect <strong>of</strong> membrane fouling <strong>th</strong>rough sludge char<strong>ac</strong>teristics.<br />
1.3 Scope <strong>of</strong> <strong>th</strong>e Study<br />
To <strong>ac</strong>hieve <strong>th</strong>e above mentioned objectives, <strong>th</strong>e following tasks are undertaken:<br />
1. Char<strong>ac</strong>terization and mixing <strong>of</strong> le<strong>ac</strong>hates obtained from Pa<strong>th</strong>um<strong>th</strong>ani landfill site<br />
(PS) and Ram-indra transfer station (RIS) was done to simulate a medium-aged<br />
le<strong>ac</strong>hate. The le<strong>ac</strong>hate COD concentration was maintained at 8,000±1,000 mg/L,<br />
BOD/COD ratio at 0.40±0.05, and TKN concentration at 1,900±100 mg/L. This<br />
laboratory simulated le<strong>ac</strong>hate was used to evaluate <strong>th</strong>e performance <strong>of</strong> <strong>th</strong>e treatment<br />
process.<br />
2. The yeast culture membrane biore<strong>ac</strong>tor (YMBR) and b<strong>ac</strong>teria culture based<br />
membrane biore<strong>ac</strong>tor (BMBR) were optimized varying <strong>th</strong>e HRT and MLSS<br />
concentrations. The optimum operational condition was evaluated in terms <strong>of</strong> organic<br />
and TKN removal efficiencies and membrane filtration performance.<br />
3. The removal <strong>of</strong> ammonia <strong>th</strong>rough ammonia stripping was carried out by varying <strong>th</strong>e<br />
pH, gradient velocity and cont<strong>ac</strong>t time. The process efficiency was evaluated in<br />
terms <strong>of</strong> ammonia removal efficiency. After <strong>th</strong>e optimization <strong>of</strong> <strong>th</strong>e operating<br />
conditions <strong>of</strong> <strong>th</strong>e ammonia stripping and <strong>th</strong>e membrane biore<strong>ac</strong>tor, <strong>th</strong>e optimum<br />
conditions were used to assess <strong>th</strong>e efficiency <strong>of</strong> <strong>th</strong>e membrane biore<strong>ac</strong>tor using <strong>th</strong>e<br />
b<strong>ac</strong>terial and yeast culture along wi<strong>th</strong> <strong>th</strong>e ammonia stripping.<br />
4. To evaluate <strong>th</strong>e inhibition effects <strong>of</strong> ammonium (NH4-N) and lead (Pb) on mixed<br />
yeast and mixed b<strong>ac</strong>teria sludge. The NH4-N concentration was varied from 200 to<br />
2,000 mg/L in bo<strong>th</strong> sludge. The lead nitrate (Pb(NO3)2) concentration in <strong>th</strong>e b<strong>ac</strong>teria<br />
system was varied from 20 to 100 mg/L while in <strong>th</strong>e yeast system was varied from 2<br />
to 25 mg/L. The inhibitory effect was measured in terms <strong>of</strong> oxygen uptake rate<br />
(OUR) using respirometric me<strong>th</strong>od.<br />
5. The sludge char<strong>ac</strong>teristics were analyzed to understand <strong>th</strong>eir relationship wi<strong>th</strong> <strong>th</strong>e<br />
EPS formation in <strong>th</strong>e membrane biore<strong>ac</strong>tor. The molecular weight cut-<strong>of</strong>f was also<br />
done in <strong>th</strong>e sludge along wi<strong>th</strong> <strong>th</strong>e fr<strong>ac</strong>tion causing COD.<br />
4
2.1 Introduction<br />
Chapter 2<br />
Literature Review<br />
A landfill is any form <strong>of</strong> waste land, ranging from an uncontrolled rubbish "dump" to<br />
a full "containment" site engineered wi<strong>th</strong> high standards to protect <strong>th</strong>e environment. The<br />
landfill is <strong>th</strong>e most economical form <strong>of</strong> solid waste disposal as adverse environmental<br />
effects and o<strong>th</strong>er risks and inconveniences are minimized, <strong>th</strong>ereby allowing waste to<br />
decompose under controlled conditions until it eventually transforms into relatively inert,<br />
stabilized material (Robinson and Maris, 1983). Most landfills can be operated<br />
satisf<strong>ac</strong>torily for at least some period in <strong>th</strong>eir lifetime in <strong>th</strong>is manner and in absence <strong>of</strong> any<br />
significant negative environmental imp<strong>ac</strong>t.<br />
Unfortunately, in warmer climates, <strong>th</strong>e increase in le<strong>ac</strong>hate production after<br />
precipitation is rapid (Lema, et al., 1988) due to rainfall exceeding <strong>th</strong>e amount which can<br />
be effectively evaporated during winter or rainy seasons. Hence, le<strong>ac</strong>hate generation needs<br />
to be controlled and effective le<strong>ac</strong>hate treatment options have to be identified in order to<br />
avoid negative imp<strong>ac</strong>ts caused by <strong>th</strong>e le<strong>ac</strong>hate.<br />
A common pr<strong>ac</strong>tice in controlling le<strong>ac</strong>hate generation is to control <strong>th</strong>e water<br />
infiltration in <strong>th</strong>e landfill by waste comp<strong>ac</strong>tion as it reduces <strong>th</strong>e infiltration rate. Fur<strong>th</strong>er, by<br />
designing water pro<strong>of</strong> covers and growing plants on <strong>th</strong>e soil covers <strong>of</strong> <strong>th</strong>e waste,<br />
infiltration can be minimized. Figure 2.1 presents a typical engineered landfill. The landfill<br />
le<strong>ac</strong>hate char<strong>ac</strong>teristic is controlled by solid waste char<strong>ac</strong>teristics, moisture content, pH,<br />
redox potential, temperature, etc. The presence <strong>of</strong> moisture is necessary for <strong>th</strong>e biological<br />
conversions wi<strong>th</strong>in <strong>th</strong>e landfill and for landfill stabilisation, which occurs when <strong>th</strong>ere is<br />
insufficient moisture. Degradation processes wi<strong>th</strong>in <strong>th</strong>e landfill are also temperature<br />
dependent. The pH and redox potential set <strong>th</strong>e conditions for <strong>th</strong>e different phases <strong>of</strong><br />
degradation and biological processes wi<strong>th</strong>in <strong>th</strong>e landfill. Thus, <strong>th</strong>e microbial composition<br />
wi<strong>th</strong>in <strong>th</strong>e landfill effectively contributes to <strong>th</strong>e landfill stabilization.<br />
After <strong>th</strong>e initial period <strong>of</strong> waste pl<strong>ac</strong>ement in a landfill, microbial processes proceed<br />
under anoxic conditions. Hydrolytic and fermentative microbial processes solubilize <strong>th</strong>e<br />
waste components during <strong>th</strong>e <strong>ac</strong>id fermentation phase producing organic <strong>ac</strong>ids, alcohols,<br />
ammonia, carbon dioxide and o<strong>th</strong>er low molecular weight compounds as major products.<br />
This process occurs at a low pH (typically around 5) and is enhanced by <strong>th</strong>e presence <strong>of</strong><br />
moisture wi<strong>th</strong>in <strong>th</strong>e landfill. After several mon<strong>th</strong>s, <strong>th</strong>e me<strong>th</strong>ane fermentation stage occurs.<br />
Me<strong>th</strong>anogenic le<strong>ac</strong>hate is neutral in pH and possesses moderate organic compounds which<br />
are not easily degradable and are fermented to yield me<strong>th</strong>ane, carbon dioxide and o<strong>th</strong>er<br />
gaseous end products (Harmsen, 1983; Farquhar, 1989).<br />
5
Perimeter<br />
Collection Pipe<br />
Cap Drainage<br />
System<br />
Filter<br />
Layer<br />
Comp<strong>ac</strong>ted<br />
soil<br />
Le<strong>ac</strong>hate Collection<br />
System<br />
Leak Detection<br />
System<br />
Figure 2.1 Schematic Representation <strong>of</strong> a Typical Engineered Landfill<br />
2.2 Solid Waste Management Pr<strong>ac</strong>tices<br />
The safe and reliable long-term disposal <strong>of</strong> solid waste is an important component in<br />
solid waste management. Municipal solid waste consists <strong>of</strong> inorganic substances such as<br />
boxes, grass clippings, furniture, clo<strong>th</strong>ing, bottles, food scraps, newspapers, and appliances<br />
along wi<strong>th</strong> organic waste. There are different me<strong>th</strong>ods employed in solid waste<br />
management. Few <strong>of</strong> <strong>th</strong>e management pr<strong>ac</strong>tices are as follows:<br />
(a) Reduction in <strong>th</strong>e exploitation <strong>of</strong> <strong>th</strong>e resources and <strong>th</strong>e minimization <strong>of</strong> waste<br />
(b) Increase in recovery/reuse by pl<strong>ac</strong>ing increased responsibility on <strong>th</strong>e producer<br />
(c) Incineration<br />
(d) Composting<br />
(e) Landfilling, etc.<br />
Landfilling or <strong>th</strong>e land disposal is today <strong>th</strong>e most commonly used me<strong>th</strong>od for waste<br />
disposal. Landfill has been <strong>th</strong>e most economical and environmentally <strong>ac</strong>ceptable me<strong>th</strong>od<br />
for <strong>th</strong>e disposal <strong>of</strong> solid waste <strong>th</strong>roughout <strong>th</strong>e world. Even wi<strong>th</strong> <strong>th</strong>e implementation <strong>of</strong><br />
waste reduction, recycling and transformation technologies, disposal <strong>of</strong> solid waste in <strong>th</strong>e<br />
landfill still remains an important component <strong>of</strong> <strong>th</strong>e solid waste management strategies.<br />
Concerns wi<strong>th</strong> <strong>th</strong>e landfilling <strong>of</strong> solid waste are related to (1) <strong>th</strong>e controlled release<br />
<strong>of</strong> landfill gases <strong>th</strong>at might migrate <strong>of</strong>f-site and cause odor and o<strong>th</strong>er potentially dangerous<br />
conditions, (2) <strong>th</strong>e imp<strong>ac</strong>t <strong>of</strong> <strong>th</strong>e uncontrolled discharge <strong>of</strong> landfill gases on <strong>th</strong>e green<br />
house effect in <strong>th</strong>e atmosphere , (3) <strong>th</strong>e uncontrolled release <strong>of</strong> le<strong>ac</strong>hate <strong>th</strong>at may migrate<br />
down to underlying groundwater or to surf<strong>ac</strong>e water, (4) <strong>th</strong>e breeding and harboring <strong>of</strong><br />
disease vectors in an improperly managed landfills, and (5) <strong>th</strong>e heal<strong>th</strong> and environmental<br />
imp<strong>ac</strong>ts associated wi<strong>th</strong> <strong>th</strong>e release <strong>of</strong> tr<strong>ac</strong>e gases arising from <strong>th</strong>e hazardous materials.<br />
2.3 Municipal Solid Waste Landfill<br />
Gas Vent<br />
Solid waste<br />
Drainage<br />
Layer<br />
Top Soil<br />
Drainage Layer<br />
Low Permeability Soil<br />
6<br />
Collection<br />
Pipes<br />
Collection<br />
Pipes<br />
Native Soil Foundation<br />
Final Soil Cover<br />
Filter Layer<br />
Barrier Layer<br />
(FML)<br />
Top Liner<br />
(FML)<br />
Upper<br />
Component<br />
Lower Component<br />
(Comp<strong>ac</strong>ted Soil)<br />
Protective Soil<br />
or Cover
In <strong>th</strong>e municipal solid waste landfill, biodegradable waste constituents are converted<br />
into intermediates and end products, primarily by initial hydrolysis to intermediate<br />
substrates which support <strong>ac</strong>idogenesis and product are subsequently utilized as precursor<br />
for gas formation during me<strong>th</strong>anogenesis in <strong>th</strong>e five degradation phases (Pohland and<br />
Harper, 1985; Pohland and Kim, 1999). Figure 2.2 represents variation in concentrations <strong>of</strong><br />
significant parameters during <strong>th</strong>e five degradation phases.<br />
High<br />
Concentration<br />
Low<br />
Redox<br />
Potential<br />
Figure 2.2 Changes in Significant Parameters during Different Phases <strong>of</strong> Landfill<br />
Stabilization (Pohland and Harper, 1985)<br />
The trend in <strong>th</strong>e degradation phase may not uniform <strong>th</strong>roughout <strong>th</strong>e landfill since<br />
<strong>th</strong>ere are certain regions in <strong>th</strong>e landfill which are dominated by a particular degradation<br />
phase. Hence, <strong>th</strong>e le<strong>ac</strong>hate generated is a combination <strong>of</strong> <strong>th</strong>e products <strong>of</strong> different<br />
microbial and physico-chemical processes taking pl<strong>ac</strong>e wi<strong>th</strong>in <strong>th</strong>e landfill.<br />
2.4 Municipal Solid Waste Landfill Le<strong>ac</strong>hate<br />
Landfill le<strong>ac</strong>hate is a high-streng<strong>th</strong> wastewater formed as a result <strong>of</strong> percolation <strong>of</strong><br />
rainwater and moisture <strong>th</strong>rough waste in a landfill. The liquid medium absorbs nutrients<br />
and contaminants from <strong>th</strong>e waste and <strong>th</strong>us posing hazard to <strong>th</strong>e receiving water bodies.<br />
Le<strong>ac</strong>hate contains many substances, depending upon <strong>th</strong>e types <strong>of</strong> waste disposed into <strong>th</strong>e<br />
landfill. Le<strong>ac</strong>hate may be toxic to life or may simply alter <strong>th</strong>e ecology <strong>of</strong> <strong>th</strong>e stream<br />
watercourse, if not removed by treatment.<br />
Depending on <strong>th</strong>e geographical and geological nature <strong>of</strong> a landfill site, le<strong>ac</strong>hate may<br />
seep into <strong>th</strong>e ground and possibly enter groundwater sources. Though part <strong>of</strong> <strong>th</strong>e<br />
contaminants from <strong>th</strong>e le<strong>ac</strong>hate can be removed by natural processes wi<strong>th</strong>in <strong>th</strong>e ground,<br />
groundwater contamination can be hazardous as drinking water sources may be affected.<br />
The simplest me<strong>th</strong>od <strong>of</strong> le<strong>ac</strong>hate treatment is disposal into <strong>th</strong>e public sewer. However,<br />
as <strong>th</strong>ere is considerable difference between <strong>th</strong>e le<strong>ac</strong>hate and domestic wastewater<br />
char<strong>ac</strong>teristics, <strong>th</strong>e volume <strong>of</strong> le<strong>ac</strong>hate discharged is limited. Fur<strong>th</strong>er, depending on<br />
7<br />
Heavy Metal<br />
Emission<br />
Carbon<br />
Emission<br />
Aerobic Acidogenic Me<strong>th</strong>anogenic Oxidation Wea<strong>th</strong>ering<br />
Degradation Phases
le<strong>ac</strong>hate char<strong>ac</strong>teristics, it may be necessary to pre-treat le<strong>ac</strong>hate prior to discharge in<br />
wastewater treatment plants so <strong>th</strong>at it does not upset <strong>th</strong>e biological process nor cause any<br />
operational and maintenance problems in <strong>th</strong>e treatment plant. In determining a treatment<br />
scheme for le<strong>ac</strong>hate treatment, it is also necessary to determine whe<strong>th</strong>er <strong>th</strong>e le<strong>ac</strong>hate<br />
effluent meets sewer or water body discharge standards.<br />
2.5 Le<strong>ac</strong>hate Composition and Char<strong>ac</strong>teristics<br />
During <strong>th</strong>e first few years (< 5 years), <strong>th</strong>e landfill is in <strong>ac</strong>idogenic phase and <strong>th</strong>e<br />
le<strong>ac</strong>hate generated is generally referred to as “young” or carbon-based le<strong>ac</strong>hate due to <strong>th</strong>e<br />
high concentration <strong>of</strong> organic carbon present. Landfill greater <strong>th</strong>an 10 years old are<br />
generally in <strong>th</strong>e me<strong>th</strong>anogenic phase and <strong>th</strong>e le<strong>ac</strong>hate generated is referred to as “old” or<br />
nitrogen-based le<strong>ac</strong>hate (Mavinic, 1998). Table.2.1 gives <strong>th</strong>e char<strong>ac</strong>teristic <strong>of</strong> le<strong>ac</strong>hate<br />
present in <strong>ac</strong>idogenic and me<strong>th</strong>anogenic phases.<br />
Table 2.1 Le<strong>ac</strong>hate Char<strong>ac</strong>teristic in Acidogenic and Me<strong>th</strong>anogenic Phase in a Landfill<br />
(Ehrig, 1998)<br />
Parameter Unit Average Range<br />
Acidogenic Phase<br />
pH 6.1 4.5 to 7.5<br />
BOD5 mg/L 13,000 4,000 to 40,000<br />
COD mg/L 22,000 6,000 to 60,000<br />
BOD5/COD 0.58 -<br />
SO4 mg/L 500 70 to 1,750<br />
Ca mg/L 1,200 10 to 2,500<br />
Mg mg/L 470 50 to 1,150<br />
Fe mg/L 780 20 to 2,100<br />
Mn mg/L 25 0.3 to 65<br />
Zn mg/L 5 0.1 to 120<br />
Me<strong>th</strong>anogenic Phase<br />
pH 8 7.5 to 9<br />
BOD5 mg/L 180 20 to 550<br />
COD mg/L 3,000 500 to 4,500<br />
BOD5/COD 0.06 -<br />
SO4 mg/L 80 10 to 420<br />
Ca mg/L 60 20 to 600<br />
Mg mg/L 180 40 to 350<br />
Fe mg/L 15 3 to 280<br />
Mn mg/L 0.7 0.03 to 45<br />
Zn mg/L 0.6 0.03 to 4<br />
The differences in le<strong>ac</strong>hate quality can be due to varied reasons, which can be<br />
categorised into four major divisions, namely <strong>th</strong>e waste (type <strong>of</strong> waste, degree <strong>of</strong><br />
decomposition, and possible seasonal variance), landfill environment (phase <strong>of</strong> degradation,<br />
humidity, temperature etc.), filling technique (comp<strong>ac</strong>ting, cover, height <strong>of</strong> landfill layers,<br />
etc.) and sampling (me<strong>th</strong>od <strong>of</strong> analysis and point <strong>of</strong> sample collection).<br />
The f<strong>ac</strong>tors affecting <strong>th</strong>e le<strong>ac</strong>hate quality is inter-related and affects <strong>th</strong>e overall<br />
variance in le<strong>ac</strong>hate quality and char<strong>ac</strong>terization. The changes in <strong>th</strong>e BOD/COD,<br />
8
COD/TOC, VS/FS and VFA/TOC ratios <strong>of</strong> le<strong>ac</strong>hate are depends greatly on <strong>th</strong>e age <strong>of</strong> <strong>th</strong>e<br />
landfill (Chian and DeWalle, 1976; Kylefors, 1997). Figure 2.3 represents <strong>th</strong>e trend <strong>of</strong><br />
le<strong>ac</strong>hate variation and over <strong>th</strong>e period <strong>of</strong> time in <strong>th</strong>e landfill. During <strong>th</strong>e initial stages, <strong>th</strong>e<br />
landfill is aerobic rich in biodegradable organic content. As <strong>th</strong>e landfill age increases, <strong>th</strong>e<br />
microorganism present in <strong>th</strong>e landfill tend to degrade <strong>th</strong>ese organic compounds into<br />
inorganic components. When anaerobic phase begins, <strong>th</strong>e COD starts increasing causing a<br />
decrease in BOD/COD ratio. This decrease in BOD/COD ratio observed, suggests <strong>th</strong>e<br />
change in biodegradability <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate wi<strong>th</strong> time. For young landfill, <strong>th</strong>e ratio is around<br />
0.5-0.8 while it re<strong>ac</strong>hes almost 0.1 in <strong>th</strong>e old landfill. The reason for low biodegradability<br />
in <strong>th</strong>e old landfill could be due to <strong>th</strong>e presence <strong>of</strong> humic and fluvic <strong>ac</strong>ids.<br />
Figure 2.3 Variation in Significant Pollutant Ratios wi<strong>th</strong> Increase in Age <strong>of</strong> <strong>th</strong>e Landfill<br />
(Chian and DeWalle, 1976)<br />
The ammonium concentration in <strong>th</strong>e le<strong>ac</strong>hate also varies wi<strong>th</strong> age <strong>of</strong> <strong>th</strong>e landfill, wi<strong>th</strong><br />
young le<strong>ac</strong>hate having a high COD (>5,000 mg/L) and low nitrogen content (< 400 mg<br />
N/L) and old le<strong>ac</strong>hate having a high concentrations <strong>of</strong> ammonia (> 400 mg N/L) and<br />
recalcitrant compounds and a low biodegradable organic fr<strong>ac</strong>tion (BOD5/COD = 0.1).<br />
Municipal solid waste landfill in Asia (except Japan) is char<strong>ac</strong>terized by 60 to 90 %<br />
organic waste and 3 to 18 % plastic (Agamu<strong>th</strong>u, 1999). Le<strong>ac</strong>hate char<strong>ac</strong>teristics <strong>of</strong> landfills<br />
surveyed in Asia including Thailand, Europe, and America are presented in Table 2.2. The<br />
char<strong>ac</strong>teristic <strong>of</strong> le<strong>ac</strong>hate from different landfill site as reported show a great variation. It is<br />
dependent on <strong>th</strong>e solid waste composition, landfill site location, and local climate. The<br />
BOD and COD concentrations decrease as <strong>th</strong>e landfill age increases.<br />
9
Table 2.2 Comparison <strong>of</strong> Le<strong>ac</strong>hate Char<strong>ac</strong>teristics <strong>of</strong> Landfills Surveyed in Asia, Europe and America<br />
Thailand 1,2 Malaysia 3<br />
Parameter<br />
Air Sabak Taman HongKong<br />
Phitsanuklok Pa<strong>th</strong>um<strong>th</strong>ani Nakhonpa<strong>th</strong>om Pa<strong>th</strong>um<strong>th</strong>ani On-Nutch Hitam Bernam Beringin<br />
4<br />
USA 5<br />
Europe 6<br />
Years in<br />
operation 1 3 4 9 20 5 7 16 6 10 1 5 16 -<br />
1,540- 1,200- 3,750- 10,700- 3,230- 800-<br />
300-<br />
Alkalinity 300-4,700 918-4,250 960-2,740 6,620 - 9,000 1,550 9,375 11,700 4,940 4,000 5,810 2,250 11,500<br />
pH 7.1-8.3 8.2-8.9 8.2-8.5 8.1 7.5 7.6-8.8 8.0-801 7.8-8.7 8.1-8.6 7.6-8.1 5.2-6.4 6.3 - 5.3-8.5<br />
1,625- 420-<br />
2,320-<br />
Chloride - 1,220-5,545 655-2,200 2,530 - 3,200<br />
410-<br />
1,820 875-2,875 2,740 522-853 600-800 1,330 70 -<br />
SS 1,950 29-110 8.4-15.7 12.5 488 1,250 111-920 420-1,150 40-53 3-124 - - - -<br />
13,930-<br />
10,300-<br />
TS 6,700 350-1,598 274-1,200 848 11,320 15,380 - 13,680 - - 100-700 - - -<br />
1,724- 1,250- 1,960- 2,460-<br />
10,000-<br />
150-<br />
COD 4,900-11,000 1,488-3,200 800-3,575 3,200 1,200 7,038 2,570 5,500 2,830 641-873 40,000 8,000 400 100,000<br />
1,120- 726-<br />
7,500-<br />
100-<br />
BOD 3,000-7,150 198-260 100-240 280 130 1,800 1,210 562-1,990 - - 28,000 4,000 80 90,000<br />
2,219- 889-<br />
TKN - 240-452 64-1,260 1,256 700 131-930 - 104-1,014 2,860 1,180 - - - 50-5,000<br />
1,190- 784-<br />
NH3-N 150-1,250 - - - - 2-32 3-8 2-47 2,700 1,156 56-482 - - 1-1500<br />
Ni 0.02-1.56 0.01-0.42 0.1 0.25 0.035 0.13-0.95 - 0-0.6 - - - - - 0.02-2.05<br />
Cd 0.037 0.02 0.001 0.002 - 0-0.23 0-0.001 0-0.15 - - -
Table 2.3 presents <strong>th</strong>e general le<strong>ac</strong>hate char<strong>ac</strong>teristics wi<strong>th</strong> age and suitability <strong>of</strong><br />
treatment options in terms <strong>of</strong> biodegradable, intermediate and stabilized landfill le<strong>ac</strong>hate.<br />
As <strong>th</strong>e young landfill is rich in organic, biological treatment is more appropriate <strong>th</strong>an<br />
physico-chemical which is suitable for <strong>th</strong>e old landfill. However, effectiveness <strong>of</strong><br />
combined treatment process for <strong>th</strong>e treatment <strong>of</strong> a le<strong>ac</strong>hate produced at specific landfill age<br />
has not been considered. Individual treatment options cannot be a long-term solution for<br />
le<strong>ac</strong>hate treatment as <strong>th</strong>ey are not effective in treating le<strong>ac</strong>hate generated at different period<br />
<strong>of</strong> time and do not adapt to changing le<strong>ac</strong>hate char<strong>ac</strong>teristics.<br />
Table 2.3 Relation between Landfill Age, Le<strong>ac</strong>hate Char<strong>ac</strong>teristics and Treatments<br />
(Amokrane, et al., 1997)<br />
Landfill Age (years) < 5 (young) 5 to 10 (medium) > 10 (old)<br />
Le<strong>ac</strong>hate Type I (biodegradable) II (intermediate) III (stabilized)<br />
pH < 6.5 6.5 to 7.5 > 7.5<br />
COD (mg/L) > 10,000 < 10,000 < 5,000<br />
COD/TOC < 2.7 2.0 to 2.7 > 2.0<br />
BOD5/COD < 0.5 0.1 to 0.5 < 0.1<br />
VFA (% TOC) > 70 5 to 30 < 5<br />
Process Treatment Efficiency<br />
Biological Treatment Good Fair Poor<br />
Chemical Oxidation Fair-poor Fair Fair<br />
Chemical Precipitation Fair-poor Fair Poor<br />
Activated Carbon Fair-poor Good-fair Good<br />
Coagulation-flocculation Fair-poor Good-fair Good<br />
Reverse Osmosis Fair Good Good<br />
2.6 Molecular Weight Distribution in Landfill Le<strong>ac</strong>hate<br />
Ultrafiltration (UF) is demonstrated to be an effective me<strong>th</strong>od for char<strong>ac</strong>terizing<br />
le<strong>ac</strong>hate on <strong>th</strong>e basis <strong>of</strong> molecular weight (MW) distribution (Gourdon, et al., 1989; Tsai,<br />
et al., 1997; Yoon, et al., 1998; Kang, et al., 2002). The UF cell is operated in a batch<br />
mode wi<strong>th</strong> nitrogen gas applied to pressurize <strong>th</strong>e system, producing a driving force for<br />
le<strong>ac</strong>hate to permeate <strong>th</strong>rough <strong>th</strong>e membranes.<br />
The organic components <strong>of</strong> le<strong>ac</strong>hate are mainly composed <strong>of</strong> water soluble<br />
substances. The suspended solid content <strong>of</strong> le<strong>ac</strong>hate is generally very low. Organic matter<br />
is dependent on <strong>th</strong>e waste composition and degree <strong>of</strong> degradation. The predominant<br />
substances in e<strong>ac</strong>h fr<strong>ac</strong>tion are given in Table 2.4.<br />
Low molecular weight organics are composed mainly <strong>of</strong> easily degradable volatile<br />
fatty <strong>ac</strong>ids, which contribute to 90 % <strong>of</strong> <strong>th</strong>is fr<strong>ac</strong>tion. The most frequently occurring fatty<br />
<strong>ac</strong>ids are: <strong>ac</strong>etic, propionic and butanic <strong>ac</strong>ids.<br />
Medium molecular weight compounds wi<strong>th</strong> molecular weight between 500 and<br />
10,000 Da are char<strong>ac</strong>teristic <strong>of</strong> fulvic <strong>ac</strong>id and humic fr<strong>ac</strong>tion present in le<strong>ac</strong>hate. This<br />
group is dominated by carboxylic and hydroxylic groups and are difficult to degrade, <strong>th</strong>us<br />
termed refr<strong>ac</strong>tory compounds. The high molecular weight organic fr<strong>ac</strong>tion varies from 0.5<br />
% in me<strong>th</strong>anogenic landfill le<strong>ac</strong>hate to 5 % in <strong>ac</strong>idogenic landfill le<strong>ac</strong>hate. These<br />
compounds are more stable and possibly originate from cellulose or lignin.<br />
11
Table 2.4 Classification <strong>of</strong> Types <strong>of</strong> Substances Using Molecular Weight Cut<strong>of</strong>f (Chian,<br />
1977; Harmsen, 1983)<br />
Division Molecular Weight Substances<br />
MW 10,000 Da High Molecular Weight Carbohydrates, Proteins<br />
Humic carbohydrate-like substances<br />
Thurman and Malcolm (1981) reported humic substances (hydrophobic <strong>ac</strong>ids)<br />
<strong>ac</strong>counted for about 50 to 90 % <strong>of</strong> <strong>th</strong>e dissolved organic carbon (DOC) present in le<strong>ac</strong>hate,<br />
whereas Imai, et al. (1995) indicated <strong>th</strong>at humic substances contributed to only 30 % <strong>of</strong> <strong>th</strong>e<br />
DOC. This implies <strong>th</strong>at non-humic substances (hydrophobic neutrals and bases,<br />
hydrophilic <strong>ac</strong>ids, neutrals and bases) may be more important <strong>th</strong>an humic substances in<br />
terms <strong>of</strong> refr<strong>ac</strong>tory char<strong>ac</strong>teristics <strong>of</strong> le<strong>ac</strong>hate.<br />
The effectiveness <strong>of</strong> a treatment process can be related to <strong>th</strong>e removal <strong>of</strong> specific<br />
organic fr<strong>ac</strong>tion in le<strong>ac</strong>hate. Bo<strong>th</strong> fulvic and humic substances are inert to biological<br />
treatment. The <strong>ac</strong>cumulation <strong>of</strong> high molecular humic carbohydrates were found to affect<br />
b<strong>ac</strong>teria flocculation (Chian and DeWalle, 1976). Therefore, fr<strong>ac</strong>tionating <strong>th</strong>e organic<br />
based on molecular weight, is an indication <strong>of</strong> <strong>th</strong>e removal efficiency and degradation<br />
potential <strong>of</strong> <strong>th</strong>e biological system.<br />
Generally, le<strong>ac</strong>hate is highly contaminated wi<strong>th</strong> organic concentrations measured as<br />
BOD and COD, wi<strong>th</strong> ammonia, halogenated hydrocarbons and heavy metals. The humic<br />
substances constitute an important group <strong>of</strong> organic matter in le<strong>ac</strong>hate (Chain, 1977;<br />
Lecoupannce, 1999). These substances can be compared wi<strong>th</strong> humic substances <strong>of</strong> natural<br />
organic matter (NOM). Humic substances are refr<strong>ac</strong>tory anionic m<strong>ac</strong>romolecules <strong>of</strong><br />
medium MW (1,000 Da MW- fluvic <strong>ac</strong>ids) to high MW (10,000 Da MW-humic <strong>ac</strong>ids).<br />
They contain bo<strong>th</strong> aromatic and aliphatic components wi<strong>th</strong> primarily carboxylic and<br />
phenolic functional groups. In many case, 500 to 1,000 Da MW fluvic-like fr<strong>ac</strong>tion<br />
increases wi<strong>th</strong> landfill ages and after a biological treatment (Mejbri, et al., 1995).<br />
Therefore, a post treatment step is usually required for complete removal <strong>of</strong> organics<br />
(Rautenb<strong>ac</strong>h and Mellis, 1994).<br />
2.7 F<strong>ac</strong>tors Affecting Le<strong>ac</strong>hate Composition<br />
In order to arrive at an appropriate treatment process, it is necessary to understand<br />
<strong>th</strong>e le<strong>ac</strong>hate char<strong>ac</strong>teristic and <strong>th</strong>e f<strong>ac</strong>tors affecting it. Generally, <strong>th</strong>e quantity <strong>of</strong> le<strong>ac</strong>hate is<br />
a direct function <strong>of</strong> <strong>th</strong>e amount <strong>of</strong> external water entering <strong>th</strong>e landfill. Landfill le<strong>ac</strong>hate is<br />
composed <strong>of</strong> <strong>th</strong>e liquid <strong>th</strong>at has entered <strong>th</strong>e landfill from external sources, such as surf<strong>ac</strong>e<br />
drainage, rainfall, groundwater and <strong>th</strong>e liquid produced from <strong>th</strong>e decomposition <strong>of</strong> waste.<br />
A generalised pattern <strong>of</strong> le<strong>ac</strong>hate formation is presented in Figure 2.4.
Ground water<br />
2.7.1 Seasonal Variation<br />
Precipitation<br />
Evaporation Evaporation<br />
Surf<strong>ac</strong>e<br />
run<strong>of</strong>f<br />
Gas Gas<br />
Storage<br />
Ground water<br />
Figure 2.4 Water Movements in <strong>th</strong>e Landfill<br />
Rainfall <strong>ac</strong>ts as a medium <strong>of</strong> transportation for le<strong>ac</strong>hing and migration <strong>of</strong><br />
contaminants from a landfill. Rainfall also provides <strong>th</strong>e required moisture content for<br />
me<strong>th</strong>ane production and biological <strong>ac</strong>tivity. Figure 2.5 shows <strong>th</strong>at <strong>th</strong>e le<strong>ac</strong>hate production<br />
varies to a great extent wi<strong>th</strong> <strong>th</strong>e amount <strong>of</strong> rainfall. It has been experienced <strong>th</strong>at in hot and<br />
humid climates, le<strong>ac</strong>hate production is much higher and varies more <strong>th</strong>an in hot and arid<br />
regions due to intensive microbial <strong>ac</strong>tivity (Trankler, et al., 2001). During dry season, <strong>th</strong>e<br />
le<strong>ac</strong>hate production is very low due to <strong>th</strong>e evaporation whereas in raining season, <strong>th</strong>e<br />
le<strong>ac</strong>hate production is related to amount <strong>of</strong> rainfall intensity. Therefore, when designing a<br />
landfill for disposal <strong>of</strong> municipal waste, and developing a treatment scheme for le<strong>ac</strong>hate<br />
treatment, <strong>th</strong>e quality and quantity <strong>of</strong> le<strong>ac</strong>hate may be influenced by climate and microbial<br />
<strong>ac</strong>tivity. On <strong>th</strong>e o<strong>th</strong>er side, <strong>th</strong>ough high rainfall leads to increased le<strong>ac</strong>hate production, it<br />
reduces le<strong>ac</strong>hate streng<strong>th</strong> due to <strong>th</strong>e dilution. The quality <strong>of</strong> le<strong>ac</strong>hate produced may be<br />
regarded as proportional to <strong>th</strong>e volume <strong>of</strong> water percolating <strong>th</strong>rough <strong>th</strong>e landfill waste.<br />
Reduction <strong>of</strong> <strong>th</strong>e quantity <strong>of</strong> water entering <strong>th</strong>e tip is <strong>th</strong>erefore <strong>of</strong> great importance in<br />
reducing <strong>th</strong>e rate <strong>of</strong> le<strong>ac</strong>hate generation (Tatsi and Zouboulis, 2002). Few researchers have<br />
measured <strong>th</strong>e temporal variation in le<strong>ac</strong>hate production as 2-45 L/s, depending largely on<br />
<strong>th</strong>e precipitation over <strong>th</strong>e landfill (Martin, et al., 1995). The influence <strong>of</strong> seasonal variation<br />
in <strong>th</strong>e landfill le<strong>ac</strong>hate quality and quantity varies from pl<strong>ac</strong>e to pl<strong>ac</strong>e which is also<br />
influenced by o<strong>th</strong>er f<strong>ac</strong>tors. It is necessary to consider <strong>th</strong>e hydrological and le<strong>ac</strong>hate quality<br />
data while suggesting a treatment for le<strong>ac</strong>hate to avoid environmental deterioration<br />
problems caused by direct disposal.<br />
13<br />
Surf<strong>ac</strong>e run<strong>of</strong>f<br />
Le<strong>ac</strong>hate
Le<strong>ac</strong>hate Production (L/d) Rainfall (mm)<br />
60<br />
40<br />
20<br />
0<br />
1/1/02 1/1/02<br />
80<br />
60<br />
40<br />
20<br />
0<br />
1/1/02 1/1/02<br />
31/1/02 31/1/02<br />
31/1/02 31/1/02<br />
2.7.2 Landfill Age<br />
2/3/02 2/3/02<br />
2/3/02 2/3/02<br />
1/4/02 1/4/02<br />
1/4/02 1/4/02<br />
1/5/02 1/5/02<br />
1/5/02 1/5/02<br />
31/5/02 31/5/02<br />
31/5/02 31/5/02<br />
Figure 2.5 Le<strong>ac</strong>hate Productions and Rainfall Variation wi<strong>th</strong> Time<br />
(Visvana<strong>th</strong>an, et al., 2003)<br />
Le<strong>ac</strong>hate sampling and analysis are <strong>of</strong> importance in assessing <strong>th</strong>e changes in<br />
le<strong>ac</strong>hate quality over a period <strong>of</strong> time. A distinction <strong>of</strong> <strong>th</strong>e age <strong>of</strong> a landfill can be made on<br />
<strong>th</strong>e basis <strong>of</strong> <strong>th</strong>e dominating degradation phase wi<strong>th</strong>in <strong>th</strong>e fill and <strong>th</strong>e composition <strong>of</strong> <strong>th</strong>e<br />
le<strong>ac</strong>hate generated. The response <strong>of</strong> landfill le<strong>ac</strong>hate quality and quantity to <strong>th</strong>e climatic<br />
variation depends on <strong>th</strong>e age <strong>of</strong> <strong>th</strong>e landfill. Few significant variations such as a decreasing<br />
trend <strong>of</strong> BOD/COD are evident as <strong>th</strong>e landfill age increases. The BOD/COD ratio depicts<br />
<strong>th</strong>e biodegradability <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate, wi<strong>th</strong> a ratio <strong>of</strong> 0.5 indicating a readily degradable<br />
organic material while a value <strong>of</strong> 0.1 or below represents a high fr<strong>ac</strong>tion <strong>of</strong> poorly<br />
degradable organic material in <strong>th</strong>e le<strong>ac</strong>hate (Table 2.3). The variation in <strong>th</strong>e quality <strong>of</strong><br />
le<strong>ac</strong>hate from a landfill in Taiwan composed <strong>of</strong> ten different units closed e<strong>ac</strong>h year is<br />
expressed in Table 2.5. From <strong>th</strong>e given table, it could be observed <strong>th</strong>at as <strong>th</strong>e landfill gets<br />
stabilized, BOD and COD concentrations reduce along wi<strong>th</strong> decrease in biodegradability.<br />
Nitrogen concentration is ano<strong>th</strong>er indicator which signifies <strong>th</strong>e age <strong>of</strong> <strong>th</strong>e landfill le<strong>ac</strong>hate<br />
as presented in Table 2.6 and 2.7. The ammonia concentration in le<strong>ac</strong>hate is high due to<br />
hydrolysis, decomposition, and fermentation <strong>of</strong> biodegradable substrate. Owing to <strong>th</strong>e<br />
anaerobic conditions wi<strong>th</strong>in landfill, nitrite and nitrate concentrations are low. In <strong>th</strong>e first<br />
few years, <strong>th</strong>e ammonia concentration tends to increase slightly over time and <strong>th</strong>en<br />
decreases as <strong>th</strong>e landfill age increases. Thus, it could be appropriate to say <strong>th</strong>at looking at<br />
<strong>th</strong>e le<strong>ac</strong>hate char<strong>ac</strong>teristic, <strong>th</strong>e age <strong>of</strong> <strong>th</strong>e landfill can be predicted to a great extent.<br />
14<br />
30/6/02 30/6/02<br />
30/6/02 30/6/02<br />
30/7/02 30/7/02<br />
30/7/02 30/7/02<br />
Date/Mon<strong>th</strong>/Year<br />
29/8/02 29/8/02<br />
29/8/02 29/8/02<br />
28/9/02 28/9/02<br />
28/9/02 28/9/02<br />
28/10/02 28/10/02<br />
28/10/02 28/10/02<br />
27/11/02 27/11/02<br />
27/11/02 27/11/02<br />
27/12/02 27/12/02<br />
27/12/02 27/12/02
Table 2.5 Variation <strong>of</strong> COD, BOD & BOD/COD wi<strong>th</strong> Increasing Landfill Ages<br />
(Ragle, 1995)<br />
Age (year) 1 2 3 4 5 6 7 8 9 10 11<br />
BOD<br />
(mg/L)<br />
25,000 10,000 290 260 240 210 190 160 130 100 80<br />
COD<br />
(mg/L)<br />
35,000 16,000 1,850 1,500 1,400 1,200 1,200 1,150 1,100 1,050 1,000<br />
BOD/COD 0.71 0.60 0.17 0.17 0.16 0.16 0.14 0.13 0.10 0.08 0.08<br />
Table 2.6 Nitrogen Concentrations from Various Sources<br />
Sample<br />
Age NH3-N Organic-N NO3-N<br />
(Year) (mg/L) (mg/L) (mg/L)<br />
Sewage 1 - 15 10 0<br />
Young le<strong>ac</strong>hate 1 1 1,000-2,000 500-1,000 0<br />
Pillar Point (Hong Kong) 6 2,563 197 2.5<br />
Ma Yau Tong (Hong Kong) 2 10 1,156 24 1.1<br />
Several sites (Germany) 1 12 1,100 - -<br />
Du Page Co. (Illinois) 1 15 860 - -<br />
Rainham (UK.) 1 24 17 - -<br />
Waterloo (Canada) 1 35 12 - -<br />
Sources: 1 McBean, et al., 1995. 2 Robinson and Luo, 1991<br />
Table 2.7 Nitrogen Concentration Ranges in <strong>th</strong>e Le<strong>ac</strong>hate for Landfill Stabilization<br />
Le<strong>ac</strong>hate/Gas<br />
Constituent<br />
Transition<br />
Phase<br />
Acid Formation<br />
Phase<br />
TKN (mg/L) 180-860 14-1,970<br />
May be low due to<br />
microbial assimilation<br />
<strong>of</strong> nitrogeneous<br />
compounds<br />
NO3-N (mg/L) 0.1-5.1<br />
Increasing due<br />
to oxidation <strong>of</strong><br />
ammonia<br />
0.05-19<br />
Decreasing due to<br />
reduction to NH3 or<br />
N2 gas<br />
NH3-N (mg/L) 120.125 2-1,030<br />
Increasing due to NO3<br />
reduction and protein<br />
breakdown<br />
NH3/TKN Ratio 0.1-0.9 0-0.98<br />
Protein breakdown;<br />
biological<br />
assimilation<br />
Nitrogen Gas (%) 70-80<br />
Influence <strong>of</strong><br />
trapped air<br />
60-80<br />
Decreasing due to<br />
dilution wi<strong>th</strong> CO2<br />
15<br />
Me<strong>th</strong>ane<br />
Fermentation<br />
Phase<br />
25-82<br />
Low due to<br />
microbial<br />
assimilation <strong>of</strong><br />
nitrogeneous<br />
compounds<br />
Absent<br />
Complete<br />
conversion to NH3<br />
or N2 gas<br />
6-430<br />
Decreasing due to<br />
biological<br />
assimilation<br />
0.1-0.84<br />
< 20<br />
Artef<strong>ac</strong>t <strong>of</strong> trapped<br />
air; denitrification<br />
Final<br />
Maturation<br />
Phase<br />
7-490<br />
0.5-0.6<br />
6-430<br />
0.5-0.97<br />
> 20<br />
Aerobic<br />
metabolism
2.7.3 Composition <strong>of</strong> <strong>th</strong>e Waste Dumped<br />
The le<strong>ac</strong>hate quality is greatly affected by refuse composition. Organic material<br />
present in <strong>th</strong>e waste mainly comprises <strong>of</strong> kitchen waste while <strong>th</strong>e inorganic constituents<br />
consists <strong>of</strong> <strong>th</strong>e plastic, glass, metal, etc. The le<strong>ac</strong>hate composition depends upon <strong>th</strong>e ratio<br />
<strong>of</strong> organic and inorganic components present in <strong>th</strong>e waste disposed in <strong>th</strong>e landfill. It is<br />
estimated <strong>th</strong>at approximately one half <strong>of</strong> <strong>th</strong>e municipal solid waste is typically composed<br />
<strong>of</strong> cellulose and hemicellulose (Fairwea<strong>th</strong>er and Barlaz, 1988; Barlaz, et al., 1989), which<br />
are considered readily degradable in <strong>th</strong>e environment. The organic content le<strong>ac</strong>hed into <strong>th</strong>e<br />
le<strong>ac</strong>hate is as a result <strong>of</strong> hydrolysis and degradation <strong>of</strong> higher molecular weight organic<br />
compounds by <strong>th</strong>e microorganisms present in <strong>th</strong>e waste. However, it has been shown <strong>th</strong>at<br />
readily degradable refuse components can sometimes persist for surprisingly long periods<br />
<strong>of</strong> time in landfills owing to several environmental f<strong>ac</strong>tors <strong>th</strong>at limit <strong>th</strong>e microbial grow<strong>th</strong><br />
(Suflita, et al., 1992; Gurijala and Suflita, 1993). The o<strong>th</strong>er f<strong>ac</strong>tors which influence <strong>th</strong>e<br />
le<strong>ac</strong>hate are <strong>th</strong>e moisture content, nutrients and organic loading in <strong>th</strong>e solid waste disposed.<br />
2.7.4 Geological Char<strong>ac</strong>teristic<br />
As <strong>th</strong>e le<strong>ac</strong>hate percolates <strong>th</strong>rough <strong>th</strong>e underlying strata, many <strong>of</strong> <strong>th</strong>e chemical and<br />
biological constituents originally contained in it will be removed by filtering and<br />
adsorptive cap<strong>ac</strong>ity <strong>of</strong> <strong>th</strong>e material composing <strong>th</strong>e strata. In general, <strong>th</strong>e extent <strong>of</strong> <strong>th</strong>is<br />
<strong>ac</strong>tion depends on <strong>th</strong>e char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e soil and especially <strong>th</strong>e clay content. Wi<strong>th</strong> <strong>th</strong>is<br />
potential, it can allow <strong>th</strong>e le<strong>ac</strong>hate to percolate into <strong>th</strong>e landfill for elimination or<br />
contamination, <strong>th</strong>ereby playing a role in affecting <strong>th</strong>e le<strong>ac</strong>hate quantity. The influence <strong>of</strong><br />
soil particle size, <strong>th</strong>e type <strong>of</strong> soil in <strong>th</strong>e underlying ground and cover material are f<strong>ac</strong>tors<br />
<strong>th</strong>at fur<strong>th</strong>er influence le<strong>ac</strong>hate production and streng<strong>th</strong>.<br />
2.7.5 Filling Technique<br />
Various f<strong>ac</strong>tors during <strong>th</strong>e filling <strong>of</strong> <strong>th</strong>e municipal solid waste in <strong>th</strong>e landfill<br />
influence <strong>th</strong>e le<strong>ac</strong>hate quality and quantity to a great extent.<br />
Filling Height: The surf<strong>ac</strong>e to volume ratio <strong>of</strong> <strong>th</strong>e waste in landfill has an imp<strong>ac</strong>t<br />
over <strong>th</strong>e infiltration, heat transfer and gas exchange occurring wi<strong>th</strong>in <strong>th</strong>e landfill. It is<br />
expected <strong>th</strong>at an increase in landfill height may limit <strong>th</strong>e affect <strong>of</strong> seasonal variation in <strong>th</strong>e<br />
le<strong>ac</strong>hate composition and can preserve <strong>th</strong>e heat from <strong>th</strong>e microbial <strong>ac</strong>tion to enhance<br />
fur<strong>th</strong>er degradation. However, aerobic conditions can be hindered due to limitations in gas<br />
transfer, <strong>th</strong>ereby converting it into anaerobic conditions, <strong>th</strong>us affecting <strong>th</strong>e le<strong>ac</strong>hate quality.<br />
Density: Waste wi<strong>th</strong> low density results in a larger volume <strong>of</strong> air infiltrating <strong>th</strong>rough<br />
<strong>th</strong>e landfill and <strong>th</strong>us promoting aerobic degradation process. This enhances <strong>th</strong>e degradation<br />
<strong>of</strong> easily degradable waste fr<strong>ac</strong>tions and complex organic and also elevates temperature<br />
wi<strong>th</strong>in <strong>th</strong>e landfill which can in turn improve conversion into inorganic constituents. A<br />
prolonged aerobic phase can lead to a drought condition wi<strong>th</strong>in <strong>th</strong>e fill and reduce<br />
degradation rates.<br />
Enhanced Stabilization: In order to reduce <strong>th</strong>e time required for le<strong>ac</strong>hate treatment,<br />
it is necessary to enhance le<strong>ac</strong>hate stabilization. Stabilization can be <strong>ac</strong>complished by two<br />
ways namely, pre-treatment by size reduction, mixing and pre-composting or by using flow<br />
systems to influence <strong>th</strong>e environmental conditions wi<strong>th</strong>in <strong>th</strong>e landfill. Continuous flow<br />
16
entails <strong>th</strong>e re-circulation <strong>of</strong> le<strong>ac</strong>hate or abstr<strong>ac</strong>tion <strong>of</strong> gas wi<strong>th</strong>in <strong>th</strong>e fill. Kylefors (1997)<br />
reported <strong>th</strong>at le<strong>ac</strong>hate re-circulation affects landfill stabilization by removing <strong>th</strong>e waste<br />
products after degradation from <strong>th</strong>e liquid phase, allowing <strong>th</strong>e addition and distribution <strong>of</strong><br />
microorganisms and nutrients wi<strong>th</strong> <strong>th</strong>e landfill and maintaining homogeneous conditions<br />
wi<strong>th</strong>in <strong>th</strong>e fill.<br />
Separation <strong>of</strong> Le<strong>ac</strong>hate: Different waste categories at municipal solid landfills will<br />
generate le<strong>ac</strong>hate wi<strong>th</strong> varying char<strong>ac</strong>teristics. Since, <strong>th</strong>is contributes to <strong>th</strong>e complexity in<br />
le<strong>ac</strong>hate treatment, it may be beneficial to sort waste in terms <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate char<strong>ac</strong>teristics<br />
in order to improve <strong>th</strong>e efficiency <strong>of</strong> <strong>th</strong>e treatment (Kylefors, 1997). This can be <strong>ac</strong>hieved<br />
by separation <strong>of</strong> le<strong>ac</strong>hate based on waste char<strong>ac</strong>teristics and by separation <strong>of</strong> le<strong>ac</strong>hate<br />
based on degradation phases. Fur<strong>th</strong>er, <strong>th</strong>e composition <strong>of</strong> <strong>th</strong>e waste landfilled can also be<br />
altered by <strong>th</strong>e addition <strong>of</strong> nutrients, seed and buffers to improve <strong>th</strong>e microbial processes<br />
wi<strong>th</strong>in <strong>th</strong>e fill. Generally, a combination <strong>of</strong> digested sewage sludge and alkaline ash is<br />
added to enhance me<strong>th</strong>anogenesis.<br />
Bottom Liners and Top Covers: The bottom liners are selected to prevent seepage<br />
<strong>of</strong> le<strong>ac</strong>hate into <strong>th</strong>e groundwater sources, whilst top covers aid in maintaining moisture<br />
wi<strong>th</strong>in <strong>th</strong>e fill as well as limiting infiltration, <strong>th</strong>us slowing down <strong>th</strong>e degradation process.<br />
2.8 Le<strong>ac</strong>hate Treatment<br />
Most solid waste disposal sites do not have <strong>th</strong>e proper le<strong>ac</strong>hate treatment system.<br />
Though varied treatment processes are used for le<strong>ac</strong>hate treatment, most <strong>of</strong> <strong>th</strong>em are not<br />
properly designed to cope wi<strong>th</strong> quantity and char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e generated le<strong>ac</strong>hate.<br />
Therefore, <strong>th</strong>e objective for le<strong>ac</strong>hate management in solid waste disposal should be to<br />
develop le<strong>ac</strong>hate treatment system having low area requirement and which is also cost<br />
effective, to identify significant f<strong>ac</strong>tors which have to be considered in le<strong>ac</strong>hate treatment<br />
system and finally to set up a suitable criteria and prepare guidelines for proper le<strong>ac</strong>hate<br />
treatment in municipal solid waste disposal dump sites so as to reduce contamination and<br />
environmental imp<strong>ac</strong>ts.<br />
Le<strong>ac</strong>hate treatment is dependent on <strong>th</strong>e quality and quantity <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate input,<br />
discharge limits or removal efficiency requirements, quantity <strong>of</strong> residual products and <strong>th</strong>eir<br />
management, site location and economics. However, high ammonia concentrations and <strong>th</strong>e<br />
typical phosphorus deficiency in landfill le<strong>ac</strong>hate hamper <strong>th</strong>e biological treatment<br />
efficiencies. Therefore, a general consensus among researchers is high nitrogen levels<br />
which are still hazardous to receiving waters and needs to be removed prior to discharge.<br />
This is generally carried out <strong>th</strong>rough biological nitrification-denitrification processes for<br />
young le<strong>ac</strong>hate and <strong>th</strong>rough physico-chemical processes for stabilised landfill le<strong>ac</strong>hate.<br />
The success <strong>of</strong> treatment process depends on <strong>th</strong>e char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate and age <strong>of</strong><br />
<strong>th</strong>e landfill.<br />
Several wastewater treatment processes have been generally used to treat landfill<br />
le<strong>ac</strong>hate (Amokrane, et al., 1997). The major biological treatment processes comprises <strong>of</strong><br />
<strong>ac</strong>tivated sludge (AS), sequencing batch re<strong>ac</strong>tor (SBR), rotating biological cont<strong>ac</strong>tor<br />
(RBC), etc and physical and chemical treatment processes comprises <strong>of</strong> oxidation,<br />
coagulation-flocculation, chemical precipitation, <strong>ac</strong>tivated carbon absorption and<br />
membrane processes.<br />
17
2.8.1 Biological Treatment Processes<br />
The majority <strong>of</strong> le<strong>ac</strong>hate treatment schemes <strong>th</strong>at have been successfully installed on<br />
landfill sites have been anaerobic biological treatment process <strong>th</strong>rough aerobic treatments<br />
have also been in use. The drawb<strong>ac</strong>ks generally experienced in biological le<strong>ac</strong>hate<br />
treatment originate from operational problems such as: foaming, metal toxicity, nutrient<br />
deficiency and sludge settling (Qasim and Chiang, 1994). Among <strong>th</strong>e various biological<br />
treatment processes, Sequencing Batch Re<strong>ac</strong>tors (SBR) have been proved as a reliable and<br />
robust me<strong>th</strong>od for le<strong>ac</strong>hate treatment to meet specified effluent consent values.<br />
Conventional aerobic systems consist <strong>of</strong> ei<strong>th</strong>er att<strong>ac</strong>hed or suspended grow<strong>th</strong> systems.<br />
The advantages and disadvantages <strong>of</strong> e<strong>ac</strong>h system is case specific. Aerobic systems range<br />
from aerated lagoons, <strong>ac</strong>tivated sludge and sequence batch re<strong>ac</strong>tors (SBR) while att<strong>ac</strong>hed<br />
grow<strong>th</strong> processes include trickling filters and rotating biological cont<strong>ac</strong>tors. Trickling<br />
filters are generally not used for le<strong>ac</strong>hate treatment when <strong>th</strong>e le<strong>ac</strong>hate contains high<br />
concentrations <strong>of</strong> organic matter (or precipitate-forming inorganic compounds), because <strong>of</strong><br />
<strong>th</strong>e large sludge production which result in clogging <strong>of</strong> <strong>th</strong>e filters.<br />
Activated Sludge Process<br />
The <strong>ac</strong>tivated sludge process is efficient in le<strong>ac</strong>hate treatment. Al<strong>th</strong>ough <strong>th</strong>ere is<br />
variability in <strong>th</strong>e le<strong>ac</strong>hate quality depending on <strong>th</strong>e source and over a period <strong>of</strong> time from a<br />
single source, biokinetic studies conducted by various researchers indicated a consistency<br />
in results as cited in Qasim and Chiang (1994) as presented in Table 2.8. A comparison <strong>of</strong><br />
biokinetic coefficients from various sources show remarkable consistency considering <strong>th</strong>e<br />
highly variation. It was found <strong>th</strong>at at any BOD concentration <strong>of</strong> landfill le<strong>ac</strong>hate, <strong>th</strong>e yield<br />
coefficient (Y) is in <strong>th</strong>e same range as domestic wastewater. This might be due to change<br />
in <strong>th</strong>e predominant species or change in <strong>th</strong>e carbon assimilation metabolism as substrate<br />
change. The biokinetic coefficients are used in <strong>th</strong>e biological grow<strong>th</strong> and substrate<br />
utilization rate equations, and are <strong>ac</strong>cepted for developing <strong>th</strong>e re<strong>ac</strong>tor design.<br />
In order to <strong>ac</strong>hieve good treatment efficiencies in <strong>ac</strong>tivated sludge processes, <strong>th</strong>e<br />
loading rate should not exceed 0.05 kg BOD5/kgTS.d. In an <strong>ac</strong>tivated sludge processes<br />
used for treating landfill le<strong>ac</strong>hate, general operation conditions are as follows:<br />
Operational conditions:<br />
MLVSS : 5,000 to 10,000 mg/L<br />
Food/Micro-organism : 0.02 to 0.06 per day<br />
Hydraulic Retention Time : 1 to 10 days<br />
Solids Retention Time : 15 to 60 days<br />
Nutrient requirements : BOD5: N: P = 100: 3.2: 0.5<br />
The process could obtain 90% to 99% BOD and COD removal and 80% to 99%<br />
metal removal.<br />
18
Table 2.8 Summary <strong>of</strong> Biokinetic Coefficient <strong>of</strong> Activated Sludge Process for Landfill<br />
Le<strong>ac</strong>hate Treatment<br />
So(BOD5)<br />
(mg/L)<br />
k<br />
(d -1 )<br />
Ks<br />
(mg/L)<br />
Y<br />
(mg/mg<br />
)<br />
kd<br />
(d -1 )<br />
19<br />
θc<br />
(d)<br />
T<br />
(°C)<br />
Reference<br />
36,000 0.75 200.0 0.33 0.0002 6.5 23 to 25 Ulo<strong>th</strong> and<br />
5<br />
Mavinic, 1977<br />
15,800* 0.6 175.0 0.40 0.050 - 22 to 24 Cook and<br />
Foree, 1974<br />
13,640 0.77 20.4 0.39 0.022 3.6 23 to 25 Zapf –Gilje and<br />
0.71 29.5 0.63 0.075 - 16 Mavinic, 1981<br />
0.46 14.6 0.50 0.028 - 9 Graham and<br />
0.29 11.8 0.43 0.008 7.5 5 Mavinic, 1979<br />
8,090 1.16 81.8 0.49 0.009 1.8 22 to 23 Wong and<br />
1.12 63.8 0.51 0.018 1.8 15 Mavinic, 1984<br />
0.51 34.6 0.51 0.006 4.0 10<br />
0.34 34.0 0.55 0.002 5.4 5<br />
1,000 4.50 99.0 0.59 0.040 0.42 22 to 23 Lee, 1979<br />
365 1.80 182.0 0.59 0.115 - 21 to 25 Palit and<br />
Qasim, 1977<br />
3,000 - - 0.44 - 1 to 20 10 Robinson and<br />
Marais, 1983<br />
2,000 0.46 180.0 0.50 0.100 2 to 10 25 Gaudy, et al.,<br />
1986<br />
Domestic 2-10 25-100 0.4-0.8 0.025- - - Tchobanoglous,<br />
Wastewater<br />
0.075<br />
et al., 2003<br />
So = BOD5 (* COD) k = substrate removal rate Ks = half-velocity constant<br />
Y = yield coefficient kd = endogenous decay coefficient Θc = solid retention time<br />
T = temperature<br />
Keenan, et al. (1984) investigated <strong>th</strong>e combined physico-chemical process wi<strong>th</strong><br />
<strong>ac</strong>tivated sludge process. It was observed <strong>th</strong>at <strong>th</strong>e reduction in ammonia by stripping and<br />
neutralization wi<strong>th</strong> H2SO4 and H3PO4 after <strong>th</strong>at entered to <strong>ac</strong>tivated sludge process. The<br />
organic matter in terms <strong>of</strong> BOD was reduced 99% and <strong>th</strong>e corresponding COD removal<br />
was 95%. The effluent BOD to COD ratio was 0.16. The reduction in ammonia was 90%<br />
and heavy metals removal ranged from 27% to 75%.<br />
Dzombak, et al. (1990) had studied <strong>th</strong>e treatment <strong>of</strong> le<strong>ac</strong>hate in an extended aeration<br />
system. The BOD/COD ratio <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate was below 0.1 which is a char<strong>ac</strong>teristic <strong>of</strong> old<br />
landfill le<strong>ac</strong>hate containing mainly refr<strong>ac</strong>tory organic compounds. Different mean-cell<br />
residence times from 15 to 60 days were investigated. It was observed <strong>th</strong>at maximum<br />
COD removal <strong>of</strong> 40% could be <strong>ac</strong>hieved wi<strong>th</strong> mean-cell residence time <strong>of</strong> 60 days. This<br />
suggested <strong>th</strong>at le<strong>ac</strong>hate from young landfills wi<strong>th</strong> organic matter containing high volatile<br />
<strong>ac</strong>ids can be more easily treated wi<strong>th</strong> an <strong>ac</strong>tivated sludge process <strong>th</strong>an old landfill le<strong>ac</strong>hate.<br />
Doyle, et al. (2001) performed <strong>th</strong>e sludge char<strong>ac</strong>terization studies in <strong>th</strong>e nitrification<br />
process used for ammonia removal in an “old” landfill le<strong>ac</strong>hate. Whilst most researchers<br />
(Knox, 1985; Robinson and Maris, 1983; Str<strong>ac</strong>han, et al., 2000) reported poor settleability
<strong>of</strong> sludge (possibly due to high ammonia and low BOD: N ratio) in <strong>th</strong>e <strong>ac</strong>tivated sludge<br />
treatment <strong>of</strong> le<strong>ac</strong>hate, Doyle, et al. (2001) reported good sludge settling wi<strong>th</strong> SVI ranging<br />
between 20 to 30 mL/g. A well-settled sludge generally exhibits an SVI <strong>of</strong> 80 to 150 mL/g.<br />
This was probably due <strong>th</strong>e presence <strong>of</strong> a high nitrifying fr<strong>ac</strong>tion in <strong>th</strong>e sludge. Fur<strong>th</strong>er, <strong>th</strong>e<br />
ability <strong>of</strong> sludge to settle well indicates <strong>th</strong>e enhanced removal efficiencies and hence,<br />
improved effluent quality.<br />
Sequencing Batch Re<strong>ac</strong>tors (SBR)<br />
Sequencing batch re<strong>ac</strong>tors (SBR) are commonly used as a biological treatment for<br />
le<strong>ac</strong>hate treatment. Several studies have been conducted to find out <strong>th</strong>e applicability <strong>of</strong><br />
SBR in le<strong>ac</strong>hate treatment. Doyle, et al. (2001) conducted a study <strong>of</strong> high-rate nitrification<br />
in SBR on a mature le<strong>ac</strong>hate obtained from a domestic landfill. The le<strong>ac</strong>hate possessed<br />
high ammonia content wi<strong>th</strong> an average concentration 880 mg/L, while <strong>th</strong>e average BOD5<br />
and COD concentrations were 60 and 1,100 mg/L, respectively. The ammonium oxidation<br />
rates upto 246 mg N/L.h and specific ammonium oxidation rates <strong>of</strong> 36 mg N/mg VSS.h<br />
were <strong>ac</strong>hieved in <strong>th</strong>is study. A complete ammonia oxidation <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate could be<br />
<strong>ac</strong>hieved wi<strong>th</strong> a HRT <strong>of</strong> 5 h.<br />
Hosomi, et al. (1989) also evaluated SBR for <strong>th</strong>e treatment <strong>of</strong> le<strong>ac</strong>hate containing<br />
high nitrogen and refr<strong>ac</strong>tory organic compounds. The advantages <strong>of</strong> <strong>th</strong>e SBR compared to<br />
nitrification-denitrification processes <strong>th</strong>at <strong>th</strong>ey are less likely to get damaged due to scale<br />
formation; easy for maintenance; sludge bulking is unlikely; by varying <strong>th</strong>e aerobic and<br />
anoxic cycles, a wide range <strong>of</strong> pollutant loads can be effectively treated, and certain nonbiodegradable<br />
halogenated organic compounds can also be degraded.<br />
Yalmaz and Ozturk (2001) conducted an investigation on <strong>th</strong>e use <strong>of</strong> SBR technology<br />
for <strong>th</strong>e treatment <strong>of</strong> high ammonia landfill le<strong>ac</strong>hate via nitrification-denitrification and<br />
anaerobic pre-treatment. The study was done in two folds: to evaluate SBR technology for<br />
<strong>th</strong>e treatment <strong>of</strong> high ammonia le<strong>ac</strong>hate and to investigate <strong>th</strong>e feasibility <strong>of</strong> using landfill<br />
le<strong>ac</strong>hate as a carbon source for denitrification. The SBR was fur<strong>th</strong>er tested for <strong>th</strong>e<br />
treatment <strong>of</strong> anaerobically pre-treated le<strong>ac</strong>hate from an up-flow anaerobic sludge blanket<br />
re<strong>ac</strong>tor (UASB). The SBR <strong>ac</strong>hieved a 90 % nitrogen removal when anaerobically pretreated<br />
le<strong>ac</strong>hate was treated while using Ca (CH3COO) 2 as a carbon source. The study<br />
revealed <strong>th</strong>at young landfill le<strong>ac</strong>hate wi<strong>th</strong> a COD/NH4-N greater <strong>th</strong>an 10 was also effective<br />
as a carbon source for denitrification. Al<strong>th</strong>ough a 2-stage combination biological treatment<br />
in <strong>th</strong>e form <strong>of</strong> UASB and SBR were used in <strong>th</strong>e treatment scheme, <strong>th</strong>e effluent emitted did<br />
not meet discharge standards and required additional post-treatment in <strong>th</strong>e form <strong>of</strong><br />
physical-chemical processes such as reverse osmosis or ozonation. This justifies findings<br />
by previous researchers who suggest <strong>th</strong>e most effective means <strong>of</strong> treating landfill le<strong>ac</strong>hate<br />
is a combination <strong>of</strong> physical-chemical and biological treatment.<br />
Rotating Biological Cont<strong>ac</strong>tor (RBC)<br />
The biological cont<strong>ac</strong>tor oxidation process is adopted to treat <strong>th</strong>e organic pollutant in<br />
<strong>th</strong>e le<strong>ac</strong>hate. Even wi<strong>th</strong> a low concentration or remarkable load fluctuation <strong>of</strong> organic<br />
pollutant, <strong>th</strong>e stable and effective treatment efficiency could be <strong>ac</strong>hieved. During an<br />
investigation conducted by Siegrist, et al. (1998) to study <strong>th</strong>e nitrogen loss in a nitrifying<br />
rotating cont<strong>ac</strong>tor to treat ammonium rich le<strong>ac</strong>hate wi<strong>th</strong>out organic carbon, it was found<br />
20
<strong>th</strong>at extensive loss <strong>of</strong> nitrogen (up to 70%) could be secured. DOC less <strong>th</strong>an 20 mg/L<br />
suggested <strong>th</strong>at <strong>th</strong>e heterotrophic denitrification could be excluded.<br />
The nitrification rate re<strong>ac</strong>hed 3-4 g NH4-N/m 2 .d at a pH <strong>of</strong> 7 to 7.3 in <strong>th</strong>e first two <strong>of</strong><br />
<strong>th</strong>ree RBC compartments. It was said <strong>th</strong>at an increasing partial pressure <strong>of</strong> oxygen and<br />
increasing ammonium concentration had favoured nitrogen removal over ammonium<br />
oxidation. The reduction <strong>of</strong> nitrite in <strong>th</strong>e aerobic bi<strong>of</strong>ilm layer close to <strong>th</strong>e surf<strong>ac</strong>e might<br />
have been <strong>th</strong>erefore coupled wi<strong>th</strong> ammonium oxidation, and probably took pl<strong>ac</strong>e in <strong>th</strong>e<br />
deeper or temporarily anoxic layer <strong>of</strong> <strong>th</strong>e bi<strong>of</strong>ilm. Henderson, et al. (1997) also found <strong>th</strong>at<br />
RBC could be effective in treating <strong>th</strong>e me<strong>th</strong>anogenic landfill le<strong>ac</strong>hate.<br />
Anaerobic Treatment<br />
The most common anaerobic treatment is <strong>th</strong>e me<strong>th</strong>anogenic degradation where <strong>th</strong>e<br />
organic matter is completely degraded to mainly me<strong>th</strong>ane and carbon dioxide. Anaerobic<br />
degradation as suggested by Kylefors (1997) follows a sequence where <strong>th</strong>e inter<strong>ac</strong>tion <strong>of</strong><br />
several different microorganisms performing hydrolysis, fermentation, <strong>ac</strong>etogenesis and<br />
me<strong>th</strong>anogenesis is required. Anaerobic processes are generally carried out in att<strong>ac</strong>hed film<br />
re<strong>ac</strong>tors. These re<strong>ac</strong>tors are insensitive to variations in loading, can retain biological solids<br />
irrespective <strong>of</strong> <strong>th</strong>e waste flow and maintain a sufficiently high solids concentration over an<br />
extended period. It has been reported <strong>th</strong>at removal efficiencies in anaerobic filters are<br />
higher <strong>th</strong>an anaerobic digesters maintained at <strong>th</strong>e same hydraulic retention time (Pohland<br />
and Kim, 1999).<br />
The main advantages <strong>of</strong> anaerobic treatment over aerobic treatment are:<br />
1. The energy requirement is lower since no oxygen is required, <strong>th</strong>us reducing <strong>th</strong>e<br />
operational cost.<br />
2. Since only 10 to 15 % <strong>of</strong> organic matter is transformed into biomass:<br />
• Low sludge production making <strong>th</strong>e sludge disposal unproblematic.<br />
• Low nutrient supplement requirement, which is beneficial for le<strong>ac</strong>hate<br />
treatment which is nutrient deficient.<br />
• Biogas production (85-90 %) favouring <strong>th</strong>e energy balance.<br />
• Possibility to treat le<strong>ac</strong>hate wi<strong>th</strong> high organic material concentration wi<strong>th</strong>out<br />
dilution as required by <strong>th</strong>e aerobic process, <strong>th</strong>us reducing <strong>th</strong>e sp<strong>ac</strong>e<br />
requirements, <strong>th</strong>e size <strong>of</strong> <strong>th</strong>e plant and capital cost.<br />
3. Anaerobic microorganisms seldom enter endogenous phase, which is important for<br />
<strong>th</strong>e treatment <strong>of</strong> le<strong>ac</strong>hate wi<strong>th</strong> variable volume and streng<strong>th</strong>.<br />
4. Anaerobic sludge is highly mineralized <strong>th</strong>an aerobic sludge, which increases its value<br />
as a fertilizer if toxic metals are removed.<br />
5. Anaerobic sludge tends to settle more easily <strong>th</strong>an aerobic sludge, where addition <strong>of</strong><br />
flocculants is required.<br />
The main drawb<strong>ac</strong>ks <strong>of</strong> anaerobic systems are:<br />
1. Working temperature above 30 °C is required for efficient kinetics.<br />
2. Complexity <strong>of</strong> start-up period and <strong>th</strong>e need for strict control <strong>of</strong> operating conditions.<br />
3. The apparently lower performance <strong>of</strong> anaerobic me<strong>th</strong>ods in elimination <strong>of</strong> heavy<br />
metals when compared wi<strong>th</strong> aerobic treatment.<br />
21
4. Need for complementary treatment in order to <strong>ac</strong>hieve high purification rates and<br />
<strong>ac</strong>ceptable effluent quality.<br />
Cameron and Koch (1980) experimented anaerobic digestion at temperature from 29<br />
to 38 o C. The initial <strong>ac</strong>climation <strong>of</strong> <strong>th</strong>is system were supplemented by adding lime to<br />
correct pH and phosphorus to maintain BOD:N:P proportion. This process could reduce<br />
BOD <strong>of</strong> 65% to 80% and heavy metals <strong>of</strong> 40% to 85%.<br />
Mendez, et al. (1989) conducted a le<strong>ac</strong>hate treatment from young landfill by using<br />
anaerobic digestion. The COD removal efficiency was 65% wi<strong>th</strong> a HRT <strong>of</strong> 8 days.<br />
Fur<strong>th</strong>ermore, <strong>th</strong>is study revealed <strong>th</strong>at <strong>th</strong>e COD removal efficiency <strong>of</strong> le<strong>ac</strong>hate from young<br />
landfill is higher <strong>th</strong>an <strong>th</strong>e le<strong>ac</strong>hate from <strong>th</strong>e old landfill, due to <strong>th</strong>e lower percent <strong>of</strong><br />
refr<strong>ac</strong>tory organic compounds.<br />
Upflow Anaerobic Sludge Blanket Re<strong>ac</strong>tor (UASB)<br />
As <strong>of</strong>ten pointed out, le<strong>ac</strong>hate varies widely in quantity and in composition, from one<br />
pl<strong>ac</strong>e to ano<strong>th</strong>er (Kennedy, et al., 1988). Such variability along wi<strong>th</strong> o<strong>th</strong>er f<strong>ac</strong>tors make <strong>th</strong>e<br />
applicability <strong>of</strong> a me<strong>th</strong>od to treat le<strong>ac</strong>hate highly dependent on <strong>th</strong>e char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e<br />
le<strong>ac</strong>hate and <strong>th</strong>e tolerance <strong>of</strong> <strong>th</strong>e me<strong>th</strong>od against changes in le<strong>ac</strong>hate quality (Henry, 1982).<br />
The UASB re<strong>ac</strong>tor has <strong>ac</strong>hieved widespread <strong>ac</strong>ceptance as a high-rate partial<br />
treatment process for high organic streng<strong>th</strong> wastewaters <strong>th</strong>roughout <strong>th</strong>e world. This helps<br />
us to <strong>ac</strong>cept UASB as a le<strong>ac</strong>hate treatment process. Blakey, et al. (1992) have studied <strong>th</strong>e<br />
influence <strong>of</strong> temperature, supply <strong>of</strong> nutrient and microorganism composition in <strong>th</strong>e re<strong>ac</strong>tor<br />
treatment efficiency. As a pre-treatment system, high rate anaerobic processes (as UASB)<br />
have been shown to be efficient in <strong>th</strong>e treatment <strong>of</strong> municipal landfill le<strong>ac</strong>hate having a<br />
COD higher <strong>th</strong>an 800 mg/L and <strong>th</strong>e BOD/COD ratio higher <strong>th</strong>an 0.3 (Kettunen, 1996).<br />
Especially, UASB re<strong>ac</strong>tors have exhibited superior performance compared to <strong>th</strong>e o<strong>th</strong>er<br />
processes at high volumetric loading rates and wi<strong>th</strong> toxic and organic shock loads.<br />
Blakey, et al. (1992) performed <strong>th</strong>e UASB wi<strong>th</strong> <strong>th</strong>e young le<strong>ac</strong>hate containing<br />
BOD/COD ratio <strong>of</strong> 0.67. The unit was operated at an average loading rate <strong>of</strong> 11 kg<br />
COD/m 3 .d wi<strong>th</strong> a HRT <strong>of</strong> 1.8 days. The average removal <strong>of</strong> COD, BOD, TOC and SS<br />
were 82%, 85%, 84%, and 90%, respectively. The biogas yield <strong>of</strong> 496 ml/g COD removed<br />
could be <strong>ac</strong>hieved. When Jans, et al. (1992) investigated UASB at loading rate <strong>of</strong> 25 kg<br />
COD/m 3 .d an efficient COD removal could be <strong>ac</strong>hieved.<br />
Nitrification and Denitrification Process<br />
The two main difficulties f<strong>ac</strong>ed by <strong>th</strong>e researchers in biologically treating <strong>th</strong>e<br />
le<strong>ac</strong>hate are:<br />
1. The le<strong>ac</strong>hate contains high nitrogen concentration wi<strong>th</strong> low COD: N ratio (Robinson<br />
and Maris, 1985)<br />
2. The high ammonia concentration causes toxicity and <strong>th</strong>e difficulty which is enhanced<br />
by phosphorous limitation (Keenan, et al., 1984).<br />
As <strong>th</strong>e high ammonium concentration affects <strong>th</strong>e le<strong>ac</strong>hate treatment, nitrification and<br />
denitrification processes play a significant role in le<strong>ac</strong>hate treatment. The ammonia toxicity<br />
occurs at a concentration <strong>of</strong> 31 to 49 mg/L (Cheung, et al., 1997). Complete removal <strong>of</strong><br />
22
ammonia could only be <strong>ac</strong>hieved when <strong>th</strong>e N: BOD5 ratio does not exceed 3.6:100. Fur<strong>th</strong>er,<br />
when ammonia concentrations exceed 200 mg/L (as N), in <strong>th</strong>e mixed liquor, <strong>th</strong>e sludge<br />
settling is also adversely affected (Robinson and Maris, 1985). Hence, removal <strong>of</strong> nitrogen<br />
and nitrogen compounds from <strong>th</strong>e le<strong>ac</strong>hate by a pre-treatment prior to biological treatment<br />
processes is <strong>of</strong> prime importance.<br />
Biological nitrification-denitrification is one <strong>of</strong> <strong>th</strong>e most economical processes for<br />
nitrogen removal. The successful application <strong>of</strong> <strong>th</strong>is system is dependent on <strong>th</strong>e microbial<br />
population, composition, char<strong>ac</strong>teristic <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate and a variety <strong>of</strong> physical and<br />
chemical parameters (Table 2.9). The process essentially consists <strong>of</strong> oxidation <strong>of</strong> ammonia<br />
to nitrates wi<strong>th</strong> nitrite as an intermediate compound and finally nitrates to nitrogen gas.<br />
Biological nitrification is preferred in absence <strong>of</strong> inhibitory substances which interfere wi<strong>th</strong><br />
<strong>th</strong>e microbial ammonium oxidation process (Doyle, et al., 2001).<br />
Table 2.9 Operational and Environmental Conditions for Nitrification-Denitrification<br />
Processes (Kylefors, 1997)<br />
Parameter Unit Nitrification Denitrification<br />
Substance<br />
transformed<br />
NH4 + NO3 -<br />
End Product NO3 - Intermediate Product NO2<br />
N2<br />
- NO2 - , N2O<br />
pH 7.5 to 8.6 6 to 8<br />
Alkalinity mmol <strong>of</strong> HCO3 - /mg <strong>of</strong> N Consuming 0.14 Producing 0.07<br />
Oxygen mg O2/L > 2 (aerobic) < 0.5 (anoxic)<br />
Organic Material mg COD/mg <strong>of</strong> N - 3<br />
Phosphorus content mg <strong>of</strong> P/g <strong>of</strong> N > 4 > 11<br />
Production <strong>of</strong> Sludge g/g <strong>of</strong> N 0.17 0.45<br />
Temperature A 10 °C increase gives about 2 times specific rate<br />
Denitrification processes occur generally in anaerobic <strong>ac</strong>tivated sludge, anaerobic<br />
filter and anaerobic lagoon. Me<strong>th</strong>anol is usually added as an organic carbon source prior to<br />
denitrification; however, dosing should be monitored to prevent hydrogen sulphide<br />
formation and its inhibition (Reeves, 1972). Endogenous respiration is not frequently used<br />
as it results in weak kinetics and requires larger volumes.<br />
In an extensive study conducted by Illies (1999) to treat high ammonia le<strong>ac</strong>hate wi<strong>th</strong><br />
a four stage nitrification-denitrification process which is biological nutrient removal, an<br />
initial ammonia concentration <strong>of</strong> 200 mg/L was step-wise increased in an attempt to<br />
improve process ability to handle high ammonia concentrations. The initial trial resulted in<br />
severe nitrification inhibition due to insufficient <strong>ac</strong>climation after increment <strong>of</strong> 300 mg/L<br />
ammonia at e<strong>ac</strong>h stage upto a final ammonia concentration <strong>of</strong> 2,300 mg/L. Fur<strong>th</strong>er,<br />
me<strong>th</strong>anol was added in <strong>th</strong>e denitrification zone simultaneously wi<strong>th</strong> increase in ammonia<br />
concentration. This led to excess <strong>of</strong> me<strong>th</strong>anol leading to inhibition <strong>of</strong> denitrification. When<br />
<strong>th</strong>e system was operated at low HRT <strong>of</strong> 1.5-1.7 h for denitrification and 3-3.4 h for<br />
nitrification wi<strong>th</strong> an SRT <strong>of</strong> 20 days, removal efficiencies were found to be greater <strong>th</strong>an<br />
90%.<br />
Bae, et al. (1997) proposed a treatment scheme consisting <strong>of</strong> an anaerobic filter (pall<br />
rings media) and 2-stage <strong>ac</strong>tivated sludge process for <strong>th</strong>e removal <strong>of</strong> ammonia and <strong>th</strong>en<br />
23
using Fenton’s treatment process which is chemical treatment using strong oxidizing agent<br />
like H2O2, FeSO4 and post-AS for COD reduction. The system was able to completely<br />
nitrify <strong>th</strong>e ammonia nitrogen wi<strong>th</strong> an initial concentration between 1,400 and 1,800 mg/L.<br />
COD was reduced from 4,000-7,000 mg/L in <strong>th</strong>e raw le<strong>ac</strong>hate to 150-200 mg/L in <strong>th</strong>e<br />
effluent. The nitrification process seemed to suggest nitrification via nitrite <strong>th</strong>an nitrate<br />
could be more advantageous due to high re<strong>ac</strong>tion rate, low organic requirements, low<br />
sludge production and low oxygen requirements. The results were in <strong>ac</strong>cordance wi<strong>th</strong> <strong>th</strong>e<br />
hypo<strong>th</strong>esis prescribed by o<strong>th</strong>er researchers (Turk and Mavinic, 1989; Abeling and Seyfried,<br />
1992).<br />
Welander, et al. (1998) investigated <strong>th</strong>e suspended carrier bi<strong>of</strong>ilm process (SCBP) in<br />
<strong>th</strong>e biological removal <strong>of</strong> nitrogen and organic matter from landfill le<strong>ac</strong>hate. In <strong>th</strong>e system,<br />
COD removal <strong>of</strong> 20 % wi<strong>th</strong> maximum volumetric nitrification and denitrification rates <strong>of</strong><br />
24 g N/m 3 .h and 55 g N/m 3 .h, respectively could be <strong>ac</strong>hieved. Total nitrogen removal was<br />
found to be 90 %. The study by Wetlander, et al. (1998) revealed <strong>th</strong>at nitrification rates<br />
could be improved by an att<strong>ac</strong>hed grow<strong>th</strong> on plastic carrier media. However, <strong>th</strong>is does not<br />
imply <strong>th</strong>at nitrification would proportionally increase wi<strong>th</strong> an increase in carrier surf<strong>ac</strong>e<br />
area since effective mass transfer <strong>of</strong> oxygen to <strong>th</strong>e bi<strong>of</strong>ilm and choice <strong>of</strong> media also<br />
governs <strong>th</strong>e process.<br />
In a study done by Imai, et al. (1993), <strong>th</strong>e feasibility <strong>of</strong> <strong>th</strong>e simultaneous removal <strong>of</strong><br />
refr<strong>ac</strong>tory organic compounds and nitrogen in an “old” landfill le<strong>ac</strong>hate was investigated<br />
by microorganisms att<strong>ac</strong>hed <strong>ac</strong>tivated carbon fluidised bed process (MAACFB). The<br />
study was conducted in anaerobic and aerobic fluidised beds arranged in series wi<strong>th</strong> a<br />
recycling <strong>of</strong> effluent from <strong>th</strong>e aerobic to <strong>th</strong>e anaerobic re<strong>ac</strong>tors for <strong>th</strong>e removal <strong>of</strong> nitrogen<br />
by denitrification. The le<strong>ac</strong>hate source was obtained from a co-disposal site <strong>of</strong> municipal<br />
and industrial waste typical <strong>of</strong> “old” le<strong>ac</strong>hate wi<strong>th</strong> a biodegradability <strong>of</strong> less <strong>th</strong>an 0.1 and<br />
total nitrogen content <strong>of</strong> 214 mg/L. The performance <strong>of</strong> <strong>th</strong>e system indicated a 60 %<br />
removal <strong>of</strong> refr<strong>ac</strong>tory organic compounds and a 70 % removal <strong>of</strong> total nitrogen.<br />
The review <strong>of</strong> biological processes highlighted <strong>th</strong>e large sp<strong>ac</strong>e, energy and volume<br />
requirements necessary for sequence batch re<strong>ac</strong>tors, however <strong>th</strong>eir advantage are immunity<br />
to shock loading and minimal operator input. Whilst biological processes are able to<br />
remove readily biodegradable organics, <strong>th</strong>e non-biodegradable matter remains untreated.<br />
Biological nitrification on <strong>th</strong>e o<strong>th</strong>er hand, is generally difficult to <strong>ac</strong>hieve in landfill<br />
le<strong>ac</strong>hate due to large amounts <strong>of</strong> inhibitory substances present in <strong>th</strong>e le<strong>ac</strong>hate. Table 2.10<br />
and Table 2.11 present a comparison <strong>of</strong> different studies wi<strong>th</strong> aerobic and anaerobic<br />
treatments, respectively. The majority <strong>of</strong> physical processes are effective in ammonia<br />
stripping but have minimal effect on removal <strong>of</strong> organics.<br />
2.8.2 Physical Treatment<br />
Physical processes include <strong>ac</strong>tivated carbon adsorption, pressure-driven membrane<br />
filtration processes, and evaporation. These processes generally cannot be applied<br />
successfully to remove <strong>th</strong>e organic material from raw le<strong>ac</strong>hate, <strong>th</strong>erefore Pohland and<br />
Harper (1985) suggested <strong>th</strong>at reverse osmosis, <strong>ac</strong>tivated carbon (PAC and GAC) and ion<br />
exchange could be more successful when used as a post-treatment for landfill le<strong>ac</strong>hate after<br />
biological treatment. However, al<strong>th</strong>ough e<strong>ac</strong>h process is coupled wi<strong>th</strong> biological system,<br />
<strong>th</strong>ey have a limited application and <strong>th</strong>erefore <strong>th</strong>ey can be even more effective when<br />
physico-chemical treatment is used as pre and post treatment for biological systems.<br />
24
Table 2.10 Treatment Efficiencies <strong>of</strong> Different Aerobic Biological Treatment Systems<br />
Processes<br />
Fill-and-draw batch<br />
SBR<br />
Aerated lagoon<br />
Activated sludge<br />
HRT<br />
(d)<br />
Temperature<br />
( O C)<br />
COD<br />
Loading<br />
(kg/m 3 -d)<br />
25<br />
Initial COD<br />
(mg/L)<br />
pH<br />
BOD/COD<br />
Ratio<br />
COD<br />
Removal<br />
(%)<br />
Initial NH4-N<br />
(mg/L)<br />
NH4-H<br />
Removal<br />
(%)<br />
Reference<br />
1-5 23-25 0.5-1.7 3,000-9,000 6.0-8.0 0.5-0.8 30-90 - - Boyle and Ham, 1974<br />
10 22 1.66 16,000 7.6-8.4 0.4 97 TN 280 92-95 Cook and Foree, 1974<br />
5 22 3.32 16,000 8.0 0.4 47 TN 280 58 Cook and Foree, 1974<br />
1 20 0.1 100-150 - - 36-38 100-330 99 Hosomi, et al., 1989<br />
0.5 25<br />
-<br />
5,295 9.1 0.4-0.5 60-68 872<br />
- Dollerer and Wilderer,<br />
1996<br />
3.2 -<br />
0.69 2,200 6.8-7.1 0.46 95<br />
35<br />
>99 Zaloum and Abbott,<br />
1997<br />
20 -<br />
0.62 12,400 - 0.4<br />
91<br />
179<br />
>99 Zaloum and Abbott,<br />
1997<br />
8.5 20-25 - 1,690 - 0.05 - 616 >99 Fisher and Fell, 1999<br />
0-20 99 Robinson and Maris,<br />
1985<br />
20 10 0.06 1,200 - 0.2<br />
41<br />
370<br />
90 Robinson and Maris,<br />
1985<br />
0.3 - - 250-1,200 - - 85-90 - - Schuk and James, 1986<br />
31 15-18 0.4 12,500 - 0.6 93-96 - - Avezzu, et al., 1992<br />
RBC 2.9 - 2.8 9,300 - 0.7 86 - - Vicevic, et al., 1992
Table 2.11 Treatment Efficiencies <strong>of</strong> Different Anaerobic Biological Treatment Systems<br />
Processes<br />
Anaerobic digestion<br />
HRT<br />
(d)<br />
Temperature<br />
( O C)<br />
26<br />
COD Loading<br />
(kg/m 3 -d)<br />
Initial COD<br />
(mg/L)<br />
pH<br />
BOD/COD<br />
Ratio<br />
COD Removal<br />
(%)<br />
Reference<br />
12.5 15 0.7 8,400 6.9-8.1 0.7 73 Boyle and Ham, 1974<br />
5-20 23 0.4-2.2 2,700-12,000 6.9-8.1 0.6-0.8 87-96 Boyle and Ham, 1974<br />
12.5 10 0.7 8,300 6.9-8.1 0.8 22 Boyle and Ham, 1974<br />
5-20 29-38 0.2-1.3 20,000-30,000 5.0-5.3 0.5 65-80 Cameron and Koch, 1980<br />
Anaerobic pond 86 20-25 - 6,280 6.6 0.7-0.8 95 Bull, et al., 1983<br />
Anaerobic filter<br />
UASB<br />
2-4 21-25 1.5-2.9 13,780 7.3-7.7 0.7 68-95 Henry, et al., 1987<br />
0.5-1.0 21-25 1.3-3.1 3,750 7.0-7.2 0.3 60-95 Henry, et al., 1987<br />
0.5-1.0 21-25 1.4-2.7 1,870 7.1-7.9 - 88-90 Henry, et al., 1987<br />
17 37 3.8 9,000 - 0.7 83 Wu, et al., 1988<br />
0.3-0.5 33-35 15-25 25,000-35,000 7.4-7.8 - 80-85 Jans, et al., 1992<br />
1.0-3.2 28-32 3.6-20 11,500-33,400 - 0.7 66-92 Blakey, et al., 1992<br />
0.6 15-20 5-15 2,800-13,000 - - 73-93 Garcia, et al., 1996<br />
0.5-1.0 - 1.2-19.7 4,800-9,840 - 0.86 77-91 Kennedy and Lentz, 2000<br />
USB/AF 2.5-5.0 30 1.3-2.5 17,000-20,000 - - 80-97 Nedwell and Reynolds, 1996<br />
AnSBR 1.5-10.0 35 0.4-9.4 3,800-15,900 7.4-8.0 0.54-0.67 65-85 Timur and Ozturk, 1999<br />
Note: USB/AF = Upflow hybrid sludge bed/fixed bed anaerobic system<br />
AnSBR = Anaerobic sequencing batch re<strong>ac</strong>tors
Activated Carbon Adsorption<br />
Granular <strong>ac</strong>tivated carbon in combination wi<strong>th</strong> biological pretreatment is <strong>th</strong>e leading<br />
technology for <strong>th</strong>e treatment <strong>of</strong> landfill le<strong>ac</strong>hate for <strong>th</strong>e removal <strong>of</strong> chemical oxygen<br />
demand (COD), adsorbable organic halogens (AOX) and o<strong>th</strong>er toxic substances. More <strong>th</strong>an<br />
130 different types <strong>of</strong> organics have been identified on spent carbon from le<strong>ac</strong>hate<br />
treatment plants. Granular <strong>ac</strong>tivated carbon is used to remove AOX and COD, bo<strong>th</strong> <strong>of</strong><br />
which are not primary focus <strong>of</strong> biological treatment systems and <strong>th</strong>erefore, <strong>th</strong>e effluent<br />
quality may be found above discharge consent levels from such treatment systems. Wi<strong>th</strong><br />
particularly dilute le<strong>ac</strong>hate, it may be operated wi<strong>th</strong> a plate separator or pressurized sand<br />
filter removing suspended solids from <strong>th</strong>e flow, in order to ensure <strong>th</strong>at <strong>th</strong>e carbon filter is<br />
not blocked wi<strong>th</strong> solids. It is necessary to ensure <strong>th</strong>at <strong>th</strong>ere are no substances in <strong>th</strong>e<br />
le<strong>ac</strong>hate which will damage <strong>th</strong>e carbon prior to selecting such a system.<br />
When Fettig (1996) studied <strong>th</strong>e treatment <strong>of</strong> landfill le<strong>ac</strong>hate by preozonation and<br />
adsorption in <strong>ac</strong>tivated carbon columns, <strong>th</strong>e data evaluation revealed <strong>th</strong>at degradation took<br />
pl<strong>ac</strong>e inside <strong>th</strong>e <strong>ac</strong>tivated carbon beds. Therefore, <strong>th</strong>e total removal efficiency <strong>of</strong> ozonated<br />
le<strong>ac</strong>hate in <strong>ac</strong>tivated carbon columns was found to be higher <strong>th</strong>an <strong>th</strong>e removal efficiency<br />
due to adsorption processes. A review <strong>of</strong> physical-chemical processes done by Qasim and<br />
Chiang (1994) indicated <strong>th</strong>at adsorption by <strong>ac</strong>tivated carbon was more effective in organic<br />
removal from raw le<strong>ac</strong>hate <strong>th</strong>an chemical precipitation wi<strong>th</strong> COD removal efficiencies <strong>of</strong><br />
59 to 94 %. The humic substances remains unaffected by <strong>ac</strong>tivated carbon treatment while,<br />
1,000 MW fluvic substances could be easily removed by <strong>ac</strong>tivated carbon.<br />
Membrane Filtration<br />
A membrane is defined as a material <strong>th</strong>at forms a <strong>th</strong>in wall capable <strong>of</strong> selectively<br />
resisting <strong>th</strong>e transfer <strong>of</strong> different constituents <strong>of</strong> a fluid and <strong>th</strong>us affecting separation <strong>of</strong> <strong>th</strong>e<br />
constituents. The principle objective <strong>of</strong> membrane manuf<strong>ac</strong>ture is to produce a material <strong>of</strong><br />
reasonable mechanical streng<strong>th</strong> <strong>th</strong>at can maintain a high <strong>th</strong>roughput <strong>of</strong> a desired permeate<br />
wi<strong>th</strong> a high degree <strong>of</strong> selectivity (Visvana<strong>th</strong>an, et al., 2000). The optimal physical structure<br />
<strong>of</strong> <strong>th</strong>e membrane material is based on a <strong>th</strong>in layer <strong>of</strong> material wi<strong>th</strong> a narrow range <strong>of</strong> pore<br />
size and a high surf<strong>ac</strong>e porosity. This concept is extended to include <strong>th</strong>e separation <strong>of</strong><br />
dissolved solutes in liquid streams and <strong>th</strong>e separation <strong>of</strong> gas mixtures for membrane<br />
filtration.<br />
The classification <strong>of</strong> membrane separation processes are based on particle and<br />
molecular size. The processes such as reverse osmosis (RO), nan<strong>of</strong>iltration (NF),<br />
ultrafiltration (UF) and micr<strong>of</strong>iltration (MF) do not generally require <strong>th</strong>e addition <strong>of</strong><br />
aggressive chemicals and can be operated at ambient temperature making <strong>th</strong>ese processes<br />
bo<strong>th</strong> an environmentally and economically attr<strong>ac</strong>tive alternative to <strong>th</strong>e conventional<br />
operating units. Table 2.12 summarizes <strong>th</strong>e various membrane processes and its separation<br />
potential. RO membranes can remove more <strong>th</strong>an 99 % <strong>of</strong> organic m<strong>ac</strong>romolecules and<br />
colloids from feed-water and up to 99 % <strong>of</strong> <strong>th</strong>e inorganic ions.<br />
27
Table 2.12 Membrane Processes (Rautenb<strong>ac</strong>h and Albrecht, 1989)<br />
Membrane Mixtures Separated Driving Force Preferably Permeating<br />
Processes<br />
Component<br />
Reverse Aqueous low Pressure difference Solvent<br />
Osmosis molecular mass<br />
solutions, Aqueous<br />
organic solutions<br />
(≤ 100 bar)<br />
Ultrafiltration M<strong>ac</strong>romolecular Pressure difference Solvent<br />
solutions,<br />
emulsions<br />
(≤ 10 bar)<br />
Micr<strong>of</strong>iltration Suspensions, Pressure difference Continuous phase<br />
(cross flow) emulsions (≤ 5 bar)<br />
Gas Permeation Gas mixtures, Pressure difference Preferably permeating<br />
water-vapour gas<br />
mixtures<br />
(≤ 80 bar)<br />
component<br />
Pervaporation Organic mixtures, Permeate side: Ratio Preferably permeating<br />
aqueous organic <strong>of</strong> partial pressure to component<br />
mixtures<br />
saturation pressure<br />
Due to high rejection ability, reverse osmosis membranes retain bo<strong>th</strong> organic and<br />
inorganic contaminants dissolved in water wi<strong>th</strong> rejection rates <strong>of</strong> 98 to 99 % <strong>th</strong>us being<br />
useful for purifying <strong>of</strong> liquid waste such as le<strong>ac</strong>hate. Permeate generated from <strong>th</strong>e reverse<br />
osmosis unit is low in inorganic and organic contaminants which meet <strong>th</strong>e discharge<br />
standards. Reverse osmosis technology was reported as <strong>th</strong>e most effective in COD removal<br />
among different physical-chemical processes evaluated. The removal efficiencies are<br />
dependent on <strong>th</strong>e choice <strong>of</strong> membrane material. Chian and DeWalle (1976) reported 50 to<br />
70 % removal <strong>of</strong> TOC wi<strong>th</strong> cellulose <strong>ac</strong>etate membranes while <strong>th</strong>e use <strong>of</strong> polye<strong>th</strong>ylamine<br />
membranes increased efficiency to 88 %.<br />
Reverse osmosis fur<strong>th</strong>er <strong>of</strong>fers <strong>th</strong>e advantage <strong>of</strong> almost complete total solid removal<br />
and is effective as ei<strong>th</strong>er a pre-treatment or a polishing treatment for a biologically or ion<br />
exchange treated effluent.<br />
Membrane filtration is less effective in treating young or <strong>ac</strong>idogenic le<strong>ac</strong>hate. The<br />
efficiency <strong>of</strong> different membrane technology in treating me<strong>th</strong>anogenic le<strong>ac</strong>hate is<br />
presented in Table 2.13. Al<strong>th</strong>ough nan<strong>of</strong>iltration and reverse osmosis are quite effective in<br />
le<strong>ac</strong>hate treatment in terms <strong>of</strong> organic, inorganic, nitrogen and AOX removal, <strong>th</strong>e<br />
disadvantage <strong>of</strong> membrane treatment system is its susceptibility to fouling and short<br />
lifetime.<br />
Table 2.13 Removal Efficiency <strong>of</strong> Moderate to High Concentrations <strong>of</strong> Pollutants Using<br />
Nan<strong>of</strong>iltration, Ultrafiltration and Reverse Osmosis (Kylefors, 1997)<br />
Parameter Reverse Osmosis Nan<strong>of</strong>iltration Ultrafiltration<br />
Removal (%) Removal (%) Removal (%)<br />
COD 95 to 99 80 to 90 25 to 60<br />
NH4(N), pH = 6.5 90 to 98 80 to 90 < 20<br />
AOX 95 to 99 70 to 90 30 to 60<br />
Chloride 90 to 99 40 to 90 < 40<br />
28
Colloidal material as well as metal precipitation can cause fouling and clogging in<br />
<strong>th</strong>e membranes. Fouling leads to an increase in osmotic pressure and hydraulic resistance,<br />
<strong>th</strong>us increasing <strong>th</strong>e energy consumption. In order to minimize <strong>th</strong>e fouling effect, <strong>th</strong>e pH<br />
can be adjusted from 4 to 7.5.<br />
Since membranes cannot retain volatile fatty <strong>ac</strong>ids, <strong>ac</strong>idogenic le<strong>ac</strong>hate is poorly<br />
treated using membrane systems. A coupling <strong>of</strong> a membrane and <strong>ac</strong>tivated sludge process<br />
to form a membrane biore<strong>ac</strong>tor may be more viable as <strong>th</strong>e membrane ensures total solids<br />
retention. For moderate to strong me<strong>th</strong>anogenic le<strong>ac</strong>hate, a good removal <strong>of</strong> several<br />
substances, including metals can be <strong>ac</strong>hieved using biore<strong>ac</strong>tors. Hence, a combination <strong>of</strong><br />
an <strong>ac</strong>tivated sludge process wi<strong>th</strong> a membrane system, <strong>th</strong>e membrane biore<strong>ac</strong>tor technology<br />
can <strong>ac</strong>hieve high treatment efficiency wi<strong>th</strong> an excellent effluent quality.<br />
The application <strong>of</strong> reverse osmosis for large-scale application had been done in<br />
Germany. The process train is as shown in Figure 2.6. The reverse osmosis system had a<br />
cap<strong>ac</strong>ity <strong>of</strong> 36m 3 /h and had been in operation for long wi<strong>th</strong> a change <strong>of</strong> a membrane after 8<br />
years (Peters, 1997). Operational pressure was ranged from 36 to 60 bars depending on<br />
feed char<strong>ac</strong>teristics. Membrane filtration took pl<strong>ac</strong>e at ambient temperature and at a<br />
permeate flux <strong>of</strong> 15 L/m 2 .h. The performance <strong>of</strong> <strong>th</strong>e plant is illustrated in Table 2.14.<br />
When a reverse osmosis in Germany was operated at a cap<strong>ac</strong>ity <strong>of</strong> 1.8m 3 /h, a salt<br />
rejection <strong>of</strong> 98 % and COD removal <strong>of</strong> 99 % could be <strong>ac</strong>hieved. The membrane was<br />
changed after 3 years <strong>of</strong> operation due to <strong>th</strong>e flux reduction. The illustrations indicated <strong>th</strong>at<br />
reverse osmosis is effective in landfill le<strong>ac</strong>hate treatment provided <strong>th</strong>at <strong>th</strong>e le<strong>ac</strong>hate<br />
char<strong>ac</strong>teristic is considered and <strong>th</strong>e membrane module modified adapted to meet <strong>th</strong>e design<br />
criteria (Peters, 1997).<br />
Le<strong>ac</strong>hate<br />
Binding<br />
Reagents<br />
Reverse Osmosis I Reverse Osmosis II<br />
RO Permeate I<br />
Solidification<br />
<strong>of</strong> Residue<br />
Concentrate I<br />
Concentrate<br />
Stabilized Materials<br />
Figure 2.6 Treatment <strong>of</strong> Landfill Le<strong>ac</strong>ahte wi<strong>th</strong> Two Stage Reverse Osmosis<br />
(Peters, 1997)<br />
29<br />
Concentrate II<br />
(Recirculation to RO I)<br />
RO Permeate II
Table 2.14 Typical Reverse Osmosis Plant Performance for Le<strong>ac</strong>hate Purification,<br />
Germany (Peters, 1997).<br />
Parameter Unit Le<strong>ac</strong>hate<br />
RO<br />
Permeate I<br />
RO<br />
Permeate II<br />
Rejection<br />
(%)<br />
pH - 7.7 6.8 6.6<br />
Electrical Conductivity µS/cm 17,250 382 20 99.9<br />
COD mg O2/L 1,797 < 15 < 15 > 99.2<br />
Ammonium mg/L 366 9.8 0.66 99.9<br />
Chloride mg/L 2,830 48.4 1.9 99.9<br />
Sodium mg/L 4,180 55.9 2.5 99.9<br />
Heavy Metals mg/L 0.25 < 0.005 < 0.005 > 98<br />
Evaporation<br />
As cited by Ehrig (1998), <strong>th</strong>rough evaporation, le<strong>ac</strong>hate can be separated into a clear<br />
liquid and a solid phase bearing <strong>th</strong>e pollutants. Pr<strong>ac</strong>tically, <strong>th</strong>is is difficult as <strong>th</strong>e solid<br />
phase or <strong>th</strong>e condensate laden wi<strong>th</strong> volatile or chlorinated organic compounds and<br />
ammonia requires fur<strong>th</strong>er treatment. Concentration and nitrogen recovery wi<strong>th</strong> <strong>th</strong>e<br />
evaporation technology is possible wi<strong>th</strong> evaporation technology. Physicalchemical<br />
le<strong>ac</strong>hate treatment plants consist <strong>of</strong> many technical points and equipments which<br />
have to be taken into <strong>ac</strong>count in <strong>th</strong>e maintenance <strong>of</strong> <strong>th</strong>e plant. Evaporation is a simpler<br />
technology wi<strong>th</strong> easy application and less complicated technical difficulties. Evaporation is<br />
also a cost-effective option.<br />
But, <strong>th</strong>e problems concerned wi<strong>th</strong> evaporation <strong>of</strong> raw le<strong>ac</strong>hate as cited by Cossu, et<br />
al. (1992) are:<br />
1. Formation <strong>of</strong> foam due to high organic content<br />
2. Encrustation and corrosion, causing equipment damage<br />
3. Fouling on <strong>th</strong>e heat-transfer surf<strong>ac</strong>e<br />
4. Need for post-treatment for removal <strong>of</strong> ammonium and halogenated organic material<br />
5. High energy costs.<br />
2.8.3 Chemical Treatment<br />
A wide scope <strong>of</strong> chemical treatment is available for le<strong>ac</strong>hate treatment. The<br />
advantages <strong>of</strong> chemical treatment me<strong>th</strong>ods in general include immediate start-up, easy<br />
automation, insensitivity to temperature changes and simplicity <strong>of</strong> plant and material<br />
requirements. However, <strong>th</strong>e advantages are outweighed by <strong>th</strong>e disadvantages <strong>of</strong> large<br />
quantities <strong>of</strong> sludge generated due to <strong>th</strong>e addition <strong>of</strong> flocculants and chemicals wi<strong>th</strong> high<br />
running costs. Thus, chemical and physical treatment is merely used as pre or posttreatment<br />
<strong>of</strong> le<strong>ac</strong>hate to complement biological processes. The various chemical treatment<br />
processes used in le<strong>ac</strong>hate treatment are coagulation, precipitation, oxidation, stripping, etc.<br />
Coagulation and Precipitation<br />
Coagulation/precipitation involves <strong>th</strong>e addition <strong>of</strong> chemicals to alter <strong>th</strong>e physical<br />
state <strong>of</strong> dissolved and suspended solids and f<strong>ac</strong>ilitate removal by sedimentation. This<br />
treatment is effective on le<strong>ac</strong>hate wi<strong>th</strong> high molecular weight organic material such as<br />
fulvic and humic <strong>ac</strong>id. Since <strong>th</strong>ese components are generally difficult to degrade<br />
30
iologically, physical-chemical processes prove beneficial wi<strong>th</strong> approximately 60 %<br />
reduction in COD for me<strong>th</strong>anogenic le<strong>ac</strong>hate.<br />
Lime as a precipitating agent can reduce colour upto 85% and remove metals <strong>th</strong>rough<br />
precipitation. Chian and DeWalle (1977) and Ho, et al. (1974) reported <strong>th</strong>at precipitation<br />
using lime could remove organic matter wi<strong>th</strong> molecular weight greater <strong>th</strong>an 50,000 Da.<br />
This particular fr<strong>ac</strong>tion is present in a low concentration in young landfills and absent in<br />
older landfills. Therefore, lime treatment is most effective in medium-age landfills. Whilst<br />
easily biodegradable fatty <strong>ac</strong>ids are however impervious to coagulation/precipitation and<br />
hence should be treated biologically.<br />
The concurrent COD and phosphorus removal via lime precipitation is independent<br />
<strong>of</strong> air flow rate. The change in colour <strong>of</strong> <strong>th</strong>e raw le<strong>ac</strong>hate from dark brown to pale yellow<br />
after precipitation indicated <strong>th</strong>e removal <strong>of</strong> <strong>th</strong>e organic fr<strong>ac</strong>tions <strong>th</strong>at contributed to <strong>th</strong>e<br />
colour (humic substances). Chian and DeWalle (1976) mentioned <strong>th</strong>at <strong>th</strong>e minimal<br />
reduction in COD (20 %) could be attributed to lime precipitation, as <strong>th</strong>e molecular weight<br />
greater <strong>th</strong>an 50,000 Da contributing to some amount <strong>of</strong> COD fr<strong>ac</strong>tion was removed.<br />
However, an increase in lime dosage did not prompt a concomitant increase in COD<br />
precipitation. Phosphorus was removed by calcium hydroxide precipitation.<br />
Chemical Oxidation<br />
Chemical oxidation technologies are useful in <strong>th</strong>e oxidative degradation or<br />
transformation <strong>of</strong> a wide range <strong>of</strong> pollutants present in drinking water, groundwater and<br />
wastewater treatment (Venkatadri and Peters, 1993). Generally, chemical oxidation<br />
processes are incorporated into treatment sequences to treat constituents <strong>of</strong> wastewaters<br />
<strong>th</strong>at are resistant to biodegradation or create toxicity in biological re<strong>ac</strong>tors. Chemical<br />
oxidation process is widely used in le<strong>ac</strong>hate treatment. A variety <strong>of</strong> chemical oxidants are<br />
used for le<strong>ac</strong>hate treatment. The various oxidants used for le<strong>ac</strong>hate treatment are hydrogen<br />
peroxide, ozone, chlorine, chlorine dioxide, hypochlorite, UV-radiation and wet oxidation.<br />
Based on <strong>th</strong>e oxidative potentials, hydroxyl radicals exhibit a stronger oxidation behavior<br />
<strong>th</strong>an ozone. Since, oxidation processes are energy intensive and expensive, <strong>th</strong>eir<br />
application is limited. Fur<strong>th</strong>er, as oxidation processes are dependent on <strong>th</strong>e stoichiometry, a<br />
large amount <strong>of</strong> oxygen is required for higher organic concentrations (Webber and Smi<strong>th</strong>,<br />
1986). Chlorine, chlorine dioxide, hypochlorite compounds are not used for oxidation due<br />
to <strong>th</strong>eir toxicity.<br />
(a) Hydrogen Peroxide<br />
Wi<strong>th</strong>out an oxygen supplement, <strong>th</strong>e oxidizing potential <strong>of</strong> hydrogen peroxide is<br />
insufficient to reduce <strong>th</strong>e content <strong>of</strong> organic compounds, especially humic substances and<br />
f<strong>ac</strong>ilitate degradation. However, hydrogen peroxide in <strong>th</strong>e presence <strong>of</strong> a suitable catalyst,<br />
usually iron salts or UV-radiation (Steensen, 1997), can form hydroxyl radicals, which<br />
have a greater oxidation potential <strong>th</strong>an hydrogen peroxide or ozone individually.<br />
According to Steensen (1993), <strong>th</strong>e economic feasibility <strong>of</strong> adopting hydrogen peroxide as a<br />
chemical oxidation option is poor as 120 to 250 kWh/kg COD removed is required.<br />
31
(b) UV-Radiation<br />
UV-radiation is generally coupled wi<strong>th</strong> hydrogen peroxide or ozone to form an<br />
oxidation complex. UV oxidize only certain organic compounds present in le<strong>ac</strong>hate and is<br />
a good disinfectant. When decomposition <strong>of</strong> dioxins in a landfill by advanced oxidation<br />
processes were studied, O3/H2O2 and UV/O3/H2O2 processes were tested to evaluate <strong>th</strong>eir<br />
performances in decomposing dioxins present in a landfill le<strong>ac</strong>hate. The data suggested<br />
<strong>th</strong>at <strong>th</strong>e UV/O3/H2O2 process had better removal efficiency <strong>of</strong> total dioxins <strong>th</strong>an O3/H2O2<br />
process in terms <strong>of</strong> toxicity (Sota, et al., 1999).<br />
(c) Ozonation<br />
The chemical oxidation wi<strong>th</strong> ozone is an innovative technology for <strong>th</strong>e treatment <strong>of</strong><br />
effluents and le<strong>ac</strong>hate <strong>th</strong>at are highly contaminated wi<strong>th</strong> organic chemicals because <strong>of</strong> its<br />
capability to completely convert <strong>th</strong>e organic contaminants to carbon dioxide.<br />
Ozone due to its strong oxidizing ability is effective and pr<strong>ac</strong>tical as a pre-treatment<br />
to remove refr<strong>ac</strong>tory species and as a polishing step to treat organic or increase <strong>th</strong>e<br />
biodegradability <strong>of</strong> refr<strong>ac</strong>tory compounds. The oxidation potential <strong>of</strong> ozone is sufficient for<br />
<strong>th</strong>e direct degradation <strong>of</strong> organic substances. The oxidation <strong>of</strong> organic compounds by<br />
ozone is a zero order re<strong>ac</strong>tion, i.e. <strong>th</strong>e re<strong>ac</strong>tion rate is constant until about 20 % <strong>of</strong> <strong>th</strong>e<br />
initial amount is left (Kylefors, 1997).<br />
Bjorkman and Mavinic (1977) conducted an extensive study <strong>of</strong> physio-chemical<br />
treatment <strong>of</strong> landfill le<strong>ac</strong>hate. The study included <strong>th</strong>e use <strong>of</strong> lime, alum, ozone and <strong>th</strong>eir<br />
various combinations for <strong>th</strong>e treatment <strong>of</strong> municipal solid waste. In <strong>th</strong>e study, after treating<br />
<strong>th</strong>e le<strong>ac</strong>hate wi<strong>th</strong> ozone, <strong>th</strong>e le<strong>ac</strong>hate was re-circulated in an attempt to improve effluent<br />
degradation. It was found <strong>th</strong>at counter-current re-circulation minimized <strong>th</strong>e foaming<br />
problem experienced in <strong>th</strong>e treatment process. However, it was concluded wi<strong>th</strong> ozone<br />
concentrations above 100 mg/L was effective in marginally reducing COD present in <strong>th</strong>e<br />
le<strong>ac</strong>hate.<br />
Gierlich and Kollb<strong>ac</strong>h (1998) reported <strong>th</strong>at ozone was effective in reducing 80 %<br />
ammonia. It was also suggested <strong>th</strong>at ozone treatment was more effective and economical if<br />
biological treatment was adopted as a pretreatment.<br />
Sludge disintegration has been commonly used as a pretreatment for sludge digestion.<br />
The digested sludge has <strong>th</strong>e advantage <strong>of</strong> controlling and reducing sludge bulking in<br />
conventional <strong>ac</strong>tivated sludge processes and <strong>th</strong>us providing an internal carbon source for<br />
biological nutrient removal. However, <strong>th</strong>e feasibility <strong>of</strong> using ozone to chemically<br />
oxygenate sludge to provide an internal carbon source for denitrification processes had not<br />
yet been investigated. This was <strong>th</strong>e research basis for a study conducted by Ahn, et al.<br />
(2001). In <strong>th</strong>e study, <strong>th</strong>e ozonated sludge resulted in a sludge mass reduction and<br />
improvement in <strong>th</strong>e settleability <strong>of</strong> <strong>th</strong>e sludge. The effect <strong>of</strong> sludge ozonation was<br />
determined in terms <strong>of</strong> ei<strong>th</strong>er mineralization or solubilization and changes in residual solid<br />
char<strong>ac</strong>teristics. Bo<strong>th</strong> <strong>th</strong>e solubilization and mineralization increases wi<strong>th</strong> increase in ozone<br />
dosage.<br />
32
Ammonia Stripping<br />
Air stripping <strong>of</strong> ammonia involves passage <strong>of</strong> large quantities <strong>of</strong> air over <strong>th</strong>e exposed<br />
surf<strong>ac</strong>e <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate, <strong>th</strong>us causing <strong>th</strong>e partial pressure <strong>of</strong> <strong>th</strong>e ammonia gas wi<strong>th</strong>in <strong>th</strong>e<br />
water to drive <strong>th</strong>e ammonia from <strong>th</strong>e liquid to <strong>th</strong>e gas phase. Ammonia stripping can also<br />
be undertaken by water falling <strong>th</strong>rough a flow <strong>of</strong> air as in stripping towers or by diffusion<br />
<strong>of</strong> air <strong>th</strong>rough water in <strong>th</strong>e form <strong>of</strong> bubbles. Stripping towers are more efficient since <strong>th</strong>ere<br />
is better cont<strong>ac</strong>t between <strong>th</strong>e gas and liquid phases when dispersion <strong>of</strong> liquid takes pl<strong>ac</strong>e in<br />
<strong>th</strong>e form <strong>of</strong> fine droplets. Since, ammonia stripping is mass transfer controlled, <strong>th</strong>e surf<strong>ac</strong>e<br />
area <strong>of</strong> <strong>th</strong>e liquid exposed must be maximised. This can be <strong>ac</strong>hieved by creating fine<br />
droplets wi<strong>th</strong> <strong>th</strong>e help <strong>of</strong> diffusers or sprayers. The process is fur<strong>th</strong>er subject to careful pH<br />
control and involves <strong>th</strong>e mass transfer <strong>of</strong> volatile contaminants from water to air.<br />
The formation <strong>of</strong> free ammonia is favoured when <strong>th</strong>e pH is above 7. At pH greater<br />
<strong>th</strong>an 10, over 85 % <strong>of</strong> ammonia present may be liberated as gas <strong>th</strong>rough agitation in <strong>th</strong>e<br />
presence <strong>of</strong> air (Reeves, 1972). Ammonium hydroxide (NH4OH) is formed as an<br />
intermediate at pH between 10 and 11 in <strong>th</strong>e re<strong>ac</strong>tion. The bubbling <strong>of</strong> air <strong>th</strong>rough<br />
ammonium hydroxide solutions results in <strong>th</strong>e freeing <strong>of</strong> ammonia gas. This process is<br />
subject to temperature and solubility interferences. Since ammonia is highly soluble in<br />
water, solubility increases at low ambient temperatures.<br />
To review <strong>th</strong>e effectiveness <strong>of</strong> ammonia stripping as a pre-treatment option for<br />
landfill le<strong>ac</strong>hate, Cheung, et al. (1997) investigated air flow rate and pH as critical<br />
parameters for <strong>th</strong>e optimisation <strong>of</strong> ammonia stripping in a stirred tank. In <strong>th</strong>e study, to<br />
evaluate <strong>th</strong>e effective pH, air flow rate <strong>of</strong> 0, 1, 5 mL/min and lime dosage <strong>of</strong> 0-10,000<br />
mg/L was varied. The study revealed an enhanced ammonia removal (86-93 %) could be<br />
<strong>ac</strong>hieved at air flow rate <strong>of</strong> 5 mL/min and pH greater <strong>th</strong>an 11. It was realized <strong>th</strong>at<br />
effectiveness <strong>of</strong> <strong>th</strong>e process was also dependent on area (A): volume (V) ratio <strong>of</strong> <strong>th</strong>e tank<br />
and le<strong>ac</strong>hate quality. The efficiencies in previous studies by o<strong>th</strong>er researchers were 40 to<br />
53 % for A: V = 23 m -1 and 19 % for A: V = 1.8 m -1 (Cheung, et al., 1997). This indicated<br />
<strong>th</strong>at <strong>th</strong>e mass transfer governed <strong>th</strong>e mechanism for ammonia stripping and it was fur<strong>th</strong>er<br />
revealed <strong>th</strong>at ammonia desorption into <strong>th</strong>e air bubbles was less significant <strong>th</strong>an <strong>th</strong>e airwater<br />
interf<strong>ac</strong>ial area. The provision <strong>of</strong> air to <strong>th</strong>e system promotes air bubble formation and<br />
turbulence at <strong>th</strong>e air-water interf<strong>ac</strong>e, which aids in increasing <strong>th</strong>e surf<strong>ac</strong>e area for ammonia<br />
removal. Thus, an indefinite increase in air flow rate could greatly enhance ammonia<br />
stripping efficiency over a short detention time. The pr<strong>ac</strong>ticality <strong>of</strong> <strong>th</strong>is appro<strong>ac</strong>h depends<br />
on <strong>th</strong>e power mixer efficiency and mass transfer rate, which should be optimised to render<br />
<strong>th</strong>e process cost-effective. Fur<strong>th</strong>er, ammonia stripping has <strong>th</strong>e advantage <strong>of</strong> precipitating<br />
organics and heavy metals present in <strong>th</strong>e le<strong>ac</strong>hate.<br />
There has been a plenty number <strong>of</strong> investigations performed on <strong>th</strong>e physico-chemical<br />
treatments to investigate <strong>th</strong>eir potential in treating le<strong>ac</strong>hate. A comparison <strong>of</strong> different<br />
studies wi<strong>th</strong> physico-chemical treatments is presented in Table 2.15.<br />
2.8.4 Natural Le<strong>ac</strong>hate Treatment Systems<br />
Natural le<strong>ac</strong>hate treatment is distinguished from conventional systems based on <strong>th</strong>e<br />
source <strong>of</strong> energy <strong>th</strong>at predominates in bo<strong>th</strong> <strong>th</strong>e systems. In conventional systems, forced<br />
aeration, mechanical mixing and chemical addition are input for <strong>th</strong>e pollutant degradation.<br />
Natural systems however, utilize renewable energy sources such as solar radiation or wind.<br />
33
Table 2.15 Treatment Efficiencies <strong>of</strong> Different Physico-chemical Treatment Systems<br />
Processes<br />
Chemical precipitation<br />
Detention<br />
Time<br />
Initial COD<br />
(mg/L)<br />
34<br />
Initial NH3<br />
(mg/L)<br />
COD<br />
Removal<br />
(%)<br />
NH3<br />
Removal<br />
(%)<br />
Reference<br />
- Alum - 800-1,500 137-330 35 - Diamadopoulos, 1994<br />
- FeCl 3 - 800-1,500 137-330 56 - Diamadopoulos, 1994<br />
- Lime - 14,900 - 13 - Cook and Foree, 1974<br />
- 550 - 10-25 - Graham, 1981<br />
- Magnesium ammonium<br />
phosphate 7 d 13,600 2,170-2,360 80 90 Kabdasli, et al., 2000<br />
Chemical oxidation<br />
- Electrochemical 4 h 4,100-5,000 2,600 92 100 Chiang, et al., 1995<br />
1,200 380 Cossu, et al., 1998<br />
- H 2O 2 + Fe(II) - 1,150 - 70 - Kim, et al., 1997<br />
30 min 1,940 151 70 81 Lin and Chang, 2000<br />
Air stripping 24 h 800-1,500 137-330 - 95 Diamadopoulos, 1994<br />
Carbon adsorption<br />
24 h 448-557 556-705 30-48 86-93 Cheung, et al., 1997<br />
17 h - 1,210-1,940 25 85 Ozturk, et al., 1999<br />
24 h - 2,170-2,360 26 85 Kabdasli, et al., 2000<br />
24 h 240 150 - 89 Marttinen, et al., 2002<br />
- Powder <strong>ac</strong>tivated carbon - 800-1,500 137-330 70 - Diamadopoulos, 1994<br />
Albers and<br />
- 742 - 43 - Kruckeberg, 1992<br />
- MAACFB - 81-157 * 214 60 70 Imai, et al., 1993<br />
- BACFB 1-4 d 81-157 * - 42-58 - Imai, et al., 1995<br />
Reverse Osmosis - 1,300 - >99 - Jans, et al., 1992<br />
- 1,000-1,500 99 - Weber and Holz, 1992<br />
- 1,800 366 >99 >99 Peters, 1997<br />
Baumgarten and<br />
- 1,300 1.9 >99 - Seyfried, 1996<br />
Note: * Dissolved organic carbon (DOC)<br />
MAACFB = Microorganism-att<strong>ac</strong>hed <strong>ac</strong>tivated carbon fluidized bed process<br />
BACFB = Biological <strong>ac</strong>tivated carbon fluidized bed process
These systems are land intensive whilst conventional systems are energy intensive. Typical<br />
natural systems used for landfill le<strong>ac</strong>hate treatment include wetlands, le<strong>ac</strong>hate recirculation<br />
and aquatic systems.<br />
Le<strong>ac</strong>hate Re-circulation<br />
Moisture addition by means <strong>of</strong> rain infiltration and le<strong>ac</strong>hate recirculation is critical to<br />
<strong>th</strong>e stabilization <strong>of</strong> landfill waste, enhancement <strong>of</strong> gas production, improvement <strong>of</strong> le<strong>ac</strong>hate<br />
quality, reducing long-term environmental consequences and liability <strong>of</strong> waste storage and<br />
improving economic viability <strong>of</strong> waste storage. The landfill effectively <strong>ac</strong>ts as an<br />
uncontrolled anaerobic filter and promotes me<strong>th</strong>anogenic conditions for <strong>th</strong>e enhancement<br />
<strong>of</strong> organic degradation (Knox, 1985; Str<strong>ac</strong>han, et al., 2000).<br />
The in situ treatment <strong>of</strong> le<strong>ac</strong>hate by recycling <strong>th</strong>e le<strong>ac</strong>hate to <strong>th</strong>e landfill reduces <strong>th</strong>e<br />
time required for biological stabilization <strong>of</strong> <strong>th</strong>e readily biodegradable le<strong>ac</strong>hate constituents<br />
and increases <strong>th</strong>e rate <strong>of</strong> biostablization <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate. Re-circulated le<strong>ac</strong>hate reduces <strong>th</strong>e<br />
stabilization time from 15 to 20 years to 2 to 3 years (Pohland and Harper, 1985). It can be<br />
suggested <strong>th</strong>at by managing <strong>th</strong>e moisture content wi<strong>th</strong>in <strong>th</strong>e landfill, <strong>th</strong>e rate and<br />
char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate generated can be controlled by diluting <strong>th</strong>e inhibitory and<br />
refr<strong>ac</strong>tory compounds. Fur<strong>th</strong>er, seed, nutrients and buffers can be added to supplement <strong>th</strong>e<br />
biological <strong>ac</strong>tivity wi<strong>th</strong>in <strong>th</strong>e landfill and <strong>th</strong>us, create an engineered biore<strong>ac</strong>tor in <strong>th</strong>e<br />
landfill. Whilst <strong>th</strong>is is effective in removing <strong>th</strong>e organic constituents in <strong>th</strong>e le<strong>ac</strong>hate, <strong>th</strong>e<br />
landfill biore<strong>ac</strong>tor has been demonstrated as being ineffective in treating elevated ammonia<br />
concentrations.<br />
Pohland (1972, 1975), Leckie, et al. (1975, 1979) and Pohland, et al. (1990),<br />
performed le<strong>ac</strong>hate recirculation studies. The results indicated a rapid decline in COD due<br />
to <strong>th</strong>e <strong>ac</strong>tive development <strong>of</strong> anaerobic me<strong>th</strong>ane forming b<strong>ac</strong>teria in <strong>th</strong>e fill, which was<br />
enhanced by recirculation <strong>of</strong> le<strong>ac</strong>hate and seeding wi<strong>th</strong> municipal sewage sludge. The<br />
COD reduction showed a similar trend as reduction in BOD, TOC, VFA, phosphate,<br />
ammonia-nitrogen and TDS.<br />
Reed Beds<br />
A reed bed system (Root zone treatment) can be designed to treat le<strong>ac</strong>hate. The<br />
wastewater to be treated in root zone treatment passes <strong>th</strong>rough <strong>th</strong>e rhizomes <strong>of</strong> <strong>th</strong>e common<br />
reed in a shallow contained bed <strong>of</strong> permeable medium. The rhizomes introduce oxygen<br />
into <strong>th</strong>e bed and as effluent percolates <strong>th</strong>rough it; microbial communities become<br />
established at <strong>th</strong>e roots and degrade contaminants. Nutrients such as nitrogen and<br />
phosphorus may also be removed directly as <strong>th</strong>e reeds utilise <strong>th</strong>em for grow<strong>th</strong>. Reed beds<br />
cannot be used as a primary treatment for le<strong>ac</strong>hate since <strong>th</strong>ey are poor at removing<br />
ammonia even from a sewage having a low concentration <strong>of</strong> 30 mg/L. Fur<strong>th</strong>er, <strong>th</strong>e<br />
<strong>ac</strong>cumulation <strong>of</strong> heavy metals wi<strong>th</strong>in <strong>th</strong>e bed may affect rhizome grow<strong>th</strong> and bed<br />
permeability. Reed beds are <strong>th</strong>erefore generally used as a polishing step for le<strong>ac</strong>hate<br />
treatment (Robinson, et al., 1992).<br />
2.8.5 Co-Treatment wi<strong>th</strong> Municipal Wastewater<br />
Current le<strong>ac</strong>hate treatment pr<strong>ac</strong>tice includes discharge <strong>of</strong> le<strong>ac</strong>hate into municipal<br />
wastewater (MWW) drains followed by <strong>th</strong>e treatment <strong>of</strong> bo<strong>th</strong> domestic wastewater and<br />
35
le<strong>ac</strong>hate in municipal wastewater treatment plants. A combined treatment may provide a<br />
better effluent quality as a result <strong>of</strong> <strong>th</strong>e maintenance <strong>of</strong> a more heterogeneous population,<br />
increased availability <strong>of</strong> nutrient and possible dilution <strong>of</strong> potential inhibitors. Ano<strong>th</strong>er<br />
advantage <strong>of</strong> co-treatment <strong>of</strong> le<strong>ac</strong>hate wi<strong>th</strong> domestic sewage is <strong>th</strong>at le<strong>ac</strong>hate contains<br />
excess <strong>of</strong> nitrogen while sewage contains excess <strong>of</strong> phosphorus which eliminates <strong>th</strong>e need<br />
for addition <strong>of</strong> nutrients. However, <strong>th</strong>e main disadvantage is <strong>th</strong>e high concentrations <strong>of</strong><br />
organic and inorganic components contributed by bo<strong>th</strong> young and old le<strong>ac</strong>hate.<br />
To review <strong>th</strong>e <strong>of</strong> co-treatment <strong>of</strong> le<strong>ac</strong>hate in MWW plants, Qasim and Chiang (1994)<br />
summarized research conducted by various researchers (Chian and DeWalle, 1977; Henry,<br />
1985; Raina and Mavinic, 1985). From <strong>th</strong>e review, it was evident <strong>th</strong>at a disagreement arose<br />
as to whe<strong>th</strong>er <strong>th</strong>is option was viable and under what conditions. Whilst Raina and Mavinic<br />
(1985) successfully treated le<strong>ac</strong>hate-MWW combinations <strong>of</strong> 20 to 40 %, Henry (1985),<br />
Chian and DeWalle (1977) and o<strong>th</strong>ers reported poor performance in <strong>th</strong>e co-treatment for<br />
le<strong>ac</strong>hate to MWW a ratio <strong>of</strong> less as 10 %. Since, <strong>th</strong>ere are contradicting results from<br />
various researchers, it is unknown whe<strong>th</strong>er <strong>th</strong>is treatment option is suitable under pr<strong>ac</strong>tical<br />
application. Al<strong>th</strong>ough BOD5, COD and heavy metal reduction is well established, <strong>th</strong>e<br />
relative proportions <strong>of</strong> le<strong>ac</strong>hate effectively treated is effected by ammonia conversions,<br />
temperature, sludge production, foaming, poor solids settleability, heavy metal<br />
<strong>ac</strong>cumulation and precipitate formation.<br />
2.9 Combined Treatment F<strong>ac</strong>ility<br />
A single treatment technology is not efficient in <strong>th</strong>e le<strong>ac</strong>hate treatment due to <strong>th</strong>e<br />
complexity involved in treating le<strong>ac</strong>hate having a varied composition and char<strong>ac</strong>teristic.<br />
Le<strong>ac</strong>hate treatment entails <strong>th</strong>e integration <strong>of</strong> several treatment processes. The coupling <strong>of</strong><br />
units for <strong>th</strong>e development <strong>of</strong> treatment sequences should be modular to allow maximum<br />
flexibility in order to vary <strong>th</strong>e order <strong>of</strong> arrangement and for addition/removal <strong>of</strong> unit<br />
operations. This effectively creates different treatment lines and <strong>th</strong>us better adapted to <strong>th</strong>e<br />
changing qualitative conditions <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate (Qasim and Chiang, 1994; Bressi and<br />
Favali, 1997).<br />
Physical-chemical treatment processes for le<strong>ac</strong>hate from young landfills are not as<br />
effective as biological processes, whereas <strong>th</strong>ey are extremely efficient for stabilized<br />
le<strong>ac</strong>hate. COD/TOC and BOD/COD ratios, absolute COD concentration and age <strong>of</strong> <strong>th</strong>e<br />
landfill are necessary determinants in <strong>th</strong>e le<strong>ac</strong>hate char<strong>ac</strong>teristics for selection <strong>of</strong><br />
appropriate treatment system. In treating le<strong>ac</strong>hate, <strong>th</strong>e treatment sequence should be able to<br />
meet ei<strong>th</strong>er <strong>th</strong>e standards for discharge in receiving water bodies or an <strong>ac</strong>ceptable limit for<br />
discharge into water treatment works. To review <strong>th</strong>e treatment sequences prior to<br />
development <strong>of</strong> optimum treatment sequence, few treatment combinations have been<br />
reviewed.<br />
2.9.1 Biological Treatment and Reverse Osmosis<br />
A treatment sequence <strong>th</strong>at is capable <strong>of</strong> removing mineralized material should<br />
include anaerobic digestion, suspended grow<strong>th</strong> biological waste treatment, partial s<strong>of</strong>tening,<br />
filtration and reverse osmosis (RO). The anaerobic digester stabilizes <strong>th</strong>e waste while <strong>th</strong>e<br />
aeration system degrades <strong>th</strong>e biological matter. The effluent could be polished in a gravity<br />
filter and demineralised in a RO unit, <strong>th</strong>us <strong>ac</strong>hieving an effluent devoid <strong>of</strong> dissolved salts<br />
and low in organics. The process train is as shown in Figure 2.7(a). Wi<strong>th</strong> increase in age,<br />
36
<strong>th</strong>e biological treatment can be repl<strong>ac</strong>ed by coagulation precipitation process followed by<br />
re-carbonation, filtration and RO in le<strong>ac</strong>hate treatment. The upgraded f<strong>ac</strong>ility could be as<br />
shown in Figure 2.7(b).<br />
Influent<br />
Influent<br />
Anaerobic<br />
Digestion<br />
To Drying Bed<br />
Gas<br />
Gas<br />
Anaerobi<br />
c<br />
A<br />
Aerobic Treatment<br />
Return Sludge<br />
Sludge to Digestion<br />
Clarifier<br />
(a)<br />
(b)<br />
Figure 2.7 Schematic Diagram <strong>of</strong> Biological Treatment and Reverse Osmosis for<br />
Le<strong>ac</strong>hate Treatment (Qasim and Chiang, 1994)<br />
2.9.2 Micr<strong>of</strong>iltration and Reverse Osmosis<br />
M<br />
Chemical Treatment<br />
Clarifie<br />
Recarbonation<br />
Incorporation <strong>of</strong> a multiple membrane system by <strong>th</strong>e combination <strong>of</strong> micr<strong>of</strong>iltration<br />
(MF) and reverse osmosis (RO) could be <strong>th</strong>e basis <strong>of</strong> <strong>th</strong>e treatment sequence developed for<br />
le<strong>ac</strong>hate treatment. The process could be suitable for le<strong>ac</strong>hate <strong>of</strong> all ages and for low to<br />
medium flow processes. The two-stage processes entails precipitation and micr<strong>of</strong>iltration<br />
for <strong>th</strong>e removal <strong>of</strong> toxic metals and suspended solids and reverse osmosis for concentration<br />
<strong>of</strong> residual organics as shown in Figure 2.8. The first step <strong>of</strong> precipitation and<br />
micr<strong>of</strong>iltration provides a simple pre-treatment for <strong>th</strong>e RO unit and <strong>th</strong>us producing a high<br />
quality effluent free <strong>of</strong> solids and dissolved organics. However, similar to o<strong>th</strong>er membrane<br />
processes, <strong>th</strong>e system is susceptible to fouling; hence, development <strong>of</strong> antifouling<br />
strategies and reduction in bi<strong>of</strong>ouling needs to be evaluated.<br />
37<br />
Granular<br />
Filter Media<br />
Granular<br />
Filter Media<br />
RO Concentrate<br />
RO Concentrate<br />
RO Permeate<br />
RO Permeate
Influent<br />
Figure 2.8 Schematic Diagram <strong>of</strong> Micr<strong>of</strong>iltration/Reverse Osmosis for Le<strong>ac</strong>hate Treatment<br />
(Qasim and Chiang, 1994)<br />
2.9.3 Denitrification-Nitrification/Ultrafiltration and Reverse Osmosis<br />
The application <strong>of</strong> membrane biore<strong>ac</strong>tors combined wi<strong>th</strong> reverse osmosis on a full<br />
scale le<strong>ac</strong>hate treatment was evaluated by PCI Memtech. The process train is as shown in<br />
Figure 2.9.<br />
Initially a RO unit was used in <strong>th</strong>e le<strong>ac</strong>hate treatment; however, combination <strong>of</strong><br />
composted wastewater and le<strong>ac</strong>hate led to a decrease in <strong>th</strong>e RO performance. Therefore, an<br />
aerobic MBR was adopted. The treatment scheme consists <strong>of</strong> separate nitrificationdenitrification<br />
re<strong>ac</strong>tors followed by an external UF membrane. The performance <strong>of</strong> <strong>th</strong>e<br />
plant is illustrated in Table 2.16.<br />
Le<strong>ac</strong>hate<br />
Flow<br />
Equalization<br />
Chemical<br />
Treatment<br />
Micr<strong>of</strong>iltration Reverse Osmosis<br />
Figure 2.9 Schematic Diagram <strong>of</strong> Denitrification-Nitrification/UF and Reverse Osmosis for<br />
Le<strong>ac</strong>hate Treatment<br />
38<br />
Solids<br />
Filter Press<br />
Denitrification Ultrafiltration<br />
Reverse Osmosis I<br />
Permeate II<br />
Discharge to<br />
Surf<strong>ac</strong>e Water<br />
Concentrate II<br />
Concentrate I<br />
(To Landfill Site)<br />
Reverse Osmosis II<br />
Effluent<br />
RO Concentrate<br />
(Recirculation)<br />
Permeate I
Table 2.16 Typical Le<strong>ac</strong>hate Composition at E<strong>ac</strong>h Stage <strong>of</strong> Le<strong>ac</strong>hate Treatment Plant<br />
Parameter (mg/L) Raw Le<strong>ac</strong>hate MBR Process RO Permeate I RO Permeate II<br />
COD<br />
TKN<br />
AOX<br />
NOx-N<br />
5,000<br />
2,000<br />
4,000<br />
-<br />
Note: AOX = Adsorbable Organic Halogens<br />
1,250<br />
100<br />
2,500<br />
<strong>ac</strong>tivity to degrade <strong>th</strong>e pollutants. Lead is one <strong>of</strong> <strong>th</strong>e important toxicant due to its abilities<br />
to causes devastating and irreversible neurological damage to children, leading to learning<br />
disabilities and damage to <strong>th</strong>e brain and nervous system. Exposures at high doses <strong>of</strong> lead<br />
can lead to coma, convulsions and dea<strong>th</strong> (LaGrega, et al., 1994). Inhibitory effects on<br />
biological treatment can be observed by reduced organic removal efficiency, and poor<br />
settling char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e microorganism in <strong>th</strong>e biological process. The toxicity <strong>of</strong> <strong>th</strong>e<br />
pollutant depends on <strong>th</strong>e concentration and type <strong>of</strong> organism present. In <strong>th</strong>is context, <strong>th</strong>e<br />
importance <strong>of</strong> toxicity or inhibition can not be neglected.<br />
Various me<strong>th</strong>ods have been described in <strong>th</strong>e literature to determine <strong>th</strong>e toxicity <strong>of</strong><br />
chemicals to microorganisms. Normally, <strong>th</strong>e toxicity <strong>of</strong> <strong>th</strong>e compound is evaluated wi<strong>th</strong><br />
organism such as algae, water flea, and fish, which is costly and time consuming. The<br />
focus <strong>of</strong> <strong>th</strong>ese me<strong>th</strong>ods is to mainly investigate <strong>th</strong>e inhibition <strong>of</strong> microbial respiration in<br />
relation to rate <strong>of</strong> oxygen consumption.<br />
In biological treatment, toxicity is generally monitored by measuring certain<br />
<strong>ac</strong>tivities <strong>of</strong> <strong>th</strong>e microorganisms. This may be observed by changes in respiratory <strong>ac</strong>tivity<br />
or biochemical tests which measure <strong>th</strong>e concentration <strong>of</strong> certain biochemical agents<br />
(Talinli and Tokta, 1994; Chen, et al., 1997; Madoni, et al., 1999). It is possible to<br />
determine <strong>th</strong>e inhibitory effects <strong>of</strong> compounds wi<strong>th</strong> <strong>th</strong>e help <strong>of</strong> feed from <strong>ac</strong>tivated sludge<br />
batch re<strong>ac</strong>tors in which a biological seed and various concentrations <strong>of</strong> inhibitors are<br />
mixed. Respiratory response is a sensitive determinant which provides a faster and more<br />
<strong>ac</strong>curate estimate <strong>of</strong> which is <strong>ac</strong>ceptable toxicity studies (Morgan and de Villiers, 1978).<br />
Toxicity detection system uses a variety <strong>of</strong> biological responses and process<br />
variables, for a wide range <strong>of</strong> biological species. The measurement <strong>of</strong> oxygen uptake,<br />
organic removal efficiency, or enzymatic <strong>ac</strong>tivity indicates biological responses to <strong>th</strong>e<br />
various conditions. A variety <strong>of</strong> toxic agents can cause different patterns <strong>of</strong> inhibition (i.e.,<br />
<strong>ac</strong>tivity per unit biomass vs toxicant concentration), on <strong>th</strong>e o<strong>th</strong>er hand, various <strong>ac</strong>tivity<br />
indicators may show different inhibition patterns for a single toxic agent (Patterson, et al.,<br />
1970).<br />
DO concentration is an important variable in <strong>th</strong>e operation <strong>of</strong> <strong>th</strong>e biological treatment.<br />
The toxicity could be tested by comparing <strong>th</strong>e respiration rate before and after addition <strong>of</strong><br />
toxicant (Temmink, et al., 1993; Madoni, et al., 1999). The results obtained from toxicity<br />
test could tell <strong>th</strong>e extent to which <strong>th</strong>e efficiency and operation <strong>of</strong> biological treatment could<br />
be affected.<br />
The respiration rate <strong>of</strong> <strong>ac</strong>tivated sludge depends on <strong>th</strong>e <strong>ac</strong>tivity <strong>of</strong> biomass which are<br />
also depends on some operating conditions in <strong>th</strong>e <strong>ac</strong>tivated sludge process. The operating<br />
conditions include mean cell residence time, organic loading rate, substrate limitation,<br />
environmental conditions such as pH, temperature, and toxic substances. The maximum<br />
respiration rate should be constant under normal operating conditions. In <strong>th</strong>e presence <strong>of</strong><br />
toxicant in <strong>th</strong>e system, <strong>th</strong>e maximum respiration rate and <strong>th</strong>e performance <strong>of</strong> <strong>th</strong>e system<br />
will decrease (Kim, et al., 1994).<br />
Temmink, et al. (1993) had conducted a study <strong>of</strong> copper (Cu) toxicity. During <strong>th</strong>e<br />
experiment, <strong>th</strong>e copper concentration in <strong>th</strong>e wastewater was increased from 25 to 200 mg/L.<br />
It was found <strong>th</strong>at <strong>th</strong>e respiration rate decreased about 30% at <strong>th</strong>e copper concentration <strong>of</strong><br />
50 mg/L. The sludge had been completely in<strong>ac</strong>tivated when <strong>th</strong>e copper concentration in <strong>th</strong>e<br />
40
influent re<strong>ac</strong>hed 200 mg/L. For <strong>th</strong>e wastewater polluted wi<strong>th</strong> phenol, phenol concentration<br />
range <strong>of</strong> 1,000-1,500 mg/L could inhibit <strong>th</strong>e respiration <strong>of</strong> <strong>th</strong>e sludge by 37%.<br />
Kim, et al. (1994) investigated <strong>th</strong>e toxicity by using respiration meter, <strong>th</strong>e data<br />
evaluation show <strong>th</strong>at <strong>th</strong>e respiration rate decreased about 20% at Cobalt (Co) concentration<br />
<strong>of</strong> 28 mg/L. It was reported <strong>th</strong>at <strong>th</strong>e grow<strong>th</strong> microorganisms was inhibited even at a<br />
concentration lower <strong>th</strong>an 0.08 mg/L. In addition, <strong>th</strong>e toxicity test was conducted in high<br />
and low pH conditions and it was found <strong>th</strong>at respiration rate decreased in bo<strong>th</strong>.<br />
Madoni, et al. (1996, 1999) investigated <strong>th</strong>e effect <strong>of</strong> lead toxicity on <strong>ac</strong>tivated<br />
sludge process. The respiration rate was inhibited 67% at <strong>th</strong>e soluble lead concentration <strong>of</strong><br />
16.9 mg/L after one hour exposure. The <strong>ac</strong>ute toxicity <strong>of</strong> lead to organisms has been<br />
reported at concentration ranging from 2 to 6 mg/L.<br />
The concentrations <strong>of</strong> various toxicants and <strong>th</strong>eir inhibitory on b<strong>ac</strong>terial respiration<br />
are summarized in Table 2.17.<br />
Table 2.17 Inhibitory Effect <strong>of</strong> Various Toxicants<br />
Toxicants Concentration Inhibition <strong>of</strong> Respiration Reference<br />
(mg/L)<br />
(%)<br />
Co 28 20 Kim, et al., 1994<br />
Cu 50 30 Temmink, et al., 1993<br />
Cd 40 50 Talinli and Tokta, 1994<br />
Ni 9 50 Talinli and Tokta, 1994<br />
Pb 16.9 67 Madoni, et al., 1999<br />
Phenol 1,000-1,500<br />
37<br />
Temmink, et al., 1993<br />
1,600<br />
50<br />
Talinli and Tokta, 1994<br />
2.11 Membrane Biore<strong>ac</strong>tors<br />
Biore<strong>ac</strong>tors are re<strong>ac</strong>tors <strong>th</strong>at convert or produce materials using functions naturally<br />
endowed to living creatures. Re<strong>ac</strong>tors using immobilized enzymes, microorganisms,<br />
animal, or plant cells and <strong>th</strong>ose applying new me<strong>th</strong>odologies such as genetic manipulation<br />
or cell fusion are typical biore<strong>ac</strong>tors (Belfort, 1989). Therefore, biore<strong>ac</strong>tors are re<strong>ac</strong>tors<br />
used to produce material wi<strong>th</strong> new or advanced technology by <strong>th</strong>e application <strong>of</strong> biological<br />
functions.<br />
The combination <strong>of</strong> membranes to biological processes for treatment has led to <strong>th</strong>e<br />
emergence <strong>of</strong> membrane biore<strong>ac</strong>tors (MBR) for separation and retention <strong>of</strong> solids; for<br />
bubble-less aeration wi<strong>th</strong>in <strong>th</strong>e biore<strong>ac</strong>tor; and for extr<strong>ac</strong>tion <strong>of</strong> priority organic pollutants<br />
from industrial contaminated water (Stephenson, et al., 2000). The membrane unit can be<br />
configured external to or immersed in <strong>th</strong>e biore<strong>ac</strong>tor (Figure 2.10).<br />
In an external circuit, <strong>th</strong>e membranes can be ei<strong>th</strong>er internally or externally skinned<br />
whilst submerged membrane re<strong>ac</strong>tors should contain membranes <strong>th</strong>at are externally<br />
skinned. The incorporating <strong>of</strong> membranes into <strong>th</strong>e biological re<strong>ac</strong>tor has eliminated <strong>th</strong>e<br />
sedimentation tank from biological treatment step associated wi<strong>th</strong> conventional wastewater<br />
treatment pr<strong>ac</strong>tices.<br />
41
Air Compressor<br />
Influent<br />
Air Diffuser<br />
Air Outlet<br />
Bio-Re<strong>ac</strong>tor<br />
Return Sludge<br />
Membrane Unit<br />
(a) (b)<br />
Figure 2.10 Schematic Diagrams <strong>of</strong> (a) External Recirculation MBR and (b) Submerged<br />
MBR System<br />
2.11.1 Membrane Configuration<br />
Effluent<br />
Influent<br />
Membrane biore<strong>ac</strong>tor configurations include: extr<strong>ac</strong>tive membrane biore<strong>ac</strong>tors<br />
(EMBR), bubble-less aeration membrane biore<strong>ac</strong>tors (MABR), recycle membrane<br />
biore<strong>ac</strong>tors and membrane separation biore<strong>ac</strong>tors.<br />
Treatment by aerobic processes is <strong>of</strong>ten limited by insufficient oxygen while using<br />
air as an oxygen source. The implementation <strong>of</strong> oxygen as opposed to air as an aeration<br />
medium would increase <strong>th</strong>e degradation rate <strong>of</strong> <strong>th</strong>e system. However, since conventional<br />
aeration devices have high power requirements and a high rate <strong>of</strong> mixing, <strong>th</strong>ese devices<br />
cannot be used wi<strong>th</strong> bi<strong>of</strong>ilm processes. MABR process uses gas permeable membranes to<br />
directly supply high purity oxygen wi<strong>th</strong>out bubble formation in a bi<strong>of</strong>ilm (Stephenson, et<br />
al., 2000). The membranes are generally configured in ei<strong>th</strong>er a plate-and-frame or hollow<br />
fibre module. However, research has focussed on <strong>th</strong>e hollow fibre arrangement wi<strong>th</strong> gas on<br />
<strong>th</strong>e lumen-side and wastewater on <strong>th</strong>e shell-side. The hollow fibre modules are preferred<br />
since <strong>th</strong>e membrane provides a high surf<strong>ac</strong>e area for oxygen transfer while occupying a<br />
small volume wi<strong>th</strong>in <strong>th</strong>e re<strong>ac</strong>tor.<br />
The membrane recycle biore<strong>ac</strong>tor consists <strong>of</strong> a re<strong>ac</strong>tion vessel operated as a stirred<br />
tank re<strong>ac</strong>tor and a membrane module containing <strong>th</strong>e membrane. The substrate and<br />
biocatalyst are added to <strong>th</strong>e re<strong>ac</strong>tion vessel in pre-determined concentrations. Thereafter,<br />
<strong>th</strong>e mixture is continuously pumped <strong>th</strong>rough <strong>th</strong>e membrane. While <strong>th</strong>e biocatalyst adheres<br />
to <strong>th</strong>e membrane surf<strong>ac</strong>e, <strong>th</strong>e medium permeates <strong>th</strong>rough <strong>th</strong>e membrane and is recycled to<br />
<strong>th</strong>e re<strong>ac</strong>tor vessel.<br />
A summary <strong>of</strong> <strong>th</strong>e advantages and disadvantages <strong>of</strong> e<strong>ac</strong>h biore<strong>ac</strong>tor configuration is<br />
presented in Table 2.18.<br />
The versatility and treatment capability <strong>of</strong> membrane biore<strong>ac</strong>tors has catapulted <strong>th</strong>e<br />
technology as a viable alternative in water and wastewater treatment over a short period.<br />
Initial design configurations <strong>of</strong> external loop systems were prone to fouling which<br />
prevented stable operation and hence was confined to small-scale operations wi<strong>th</strong> limited<br />
value and applicability.<br />
42<br />
Feed Tank<br />
Compressed Air Effluent<br />
Level Control<br />
Tank<br />
Membrane<br />
Air Diffuser
Table 2.18 Advantages and Disadvantages <strong>of</strong> Membrane Biore<strong>ac</strong>tors (Stephenson, et al.,<br />
2000)<br />
Advantages Disadvantages<br />
Membrane Separation Biore<strong>ac</strong>tors<br />
Small footprint<br />
Complete solids removal from effluent<br />
Effluent disinfection<br />
Combined COD, solids and nutrient removal in a<br />
single unit<br />
High loading rate cap<strong>ac</strong>ity<br />
Low/zero sludge production<br />
Rapid start up<br />
Sludge bulking not a problem<br />
Modular/ retr<strong>of</strong>it<br />
Membrane Aeration Biore<strong>ac</strong>tors<br />
High oxygen utilization<br />
Highly efficient energy utilization<br />
Small footprint<br />
Feed-forward control <strong>of</strong> O demand<br />
Modular/retr<strong>of</strong>it<br />
Extr<strong>ac</strong>tive Membrane Biore<strong>ac</strong>tors<br />
Treatment <strong>of</strong> toxic industrial effluent<br />
Small effluent<br />
Modular/retr<strong>of</strong>it<br />
Isolation <strong>of</strong> b<strong>ac</strong>teria from wastewater<br />
43<br />
Aeration limitations<br />
Membrane fouling<br />
Membrane costs<br />
Susceptible to membrane<br />
fouling<br />
High capital costs<br />
Unproven at full-scale<br />
Process complexity<br />
High capital cost<br />
Unproven at full-scale<br />
Process complexity<br />
Systems were designed wi<strong>th</strong> long HRT and SRT resulting in little or no sludge<br />
production. The basic problem wi<strong>th</strong> membrane biore<strong>ac</strong>tor technology in <strong>th</strong>e early<br />
development stages was <strong>th</strong>e high energy costs and <strong>th</strong>e high cost <strong>of</strong> membranes.<br />
Application was <strong>th</strong>erefore limited to small industrial and commercial systems <strong>th</strong>at used<br />
large diameter membranes wi<strong>th</strong> little pre-screening and could handle large concentrations<br />
<strong>of</strong> solids in <strong>th</strong>e mixed liquor typically <strong>of</strong> 20,000 to 40,000 mg/L.<br />
The membrane biore<strong>ac</strong>tor was revolutionised when focus shifted to immersed<br />
membrane biore<strong>ac</strong>tor systems. The membrane was immersed directly into <strong>th</strong>e <strong>ac</strong>tivated<br />
sludge tank wi<strong>th</strong> constant flow maintained by an upstream level control tank. The system<br />
SRT was maintained, however, MLSS concentrations were lowered to 15,000 from 25,000<br />
mg/L. The evolutions away from <strong>th</strong>e external circuit reduced energy consumption and<br />
broaden <strong>th</strong>e membrane scope to large-scale varied applications. However, as cited in<br />
McCann (2002), <strong>th</strong>e membrane costs were high; fluxes were low and a standardised<br />
operating protocol incorporating flux enhancement and chemical cleaning was not<br />
established.<br />
Later, large-scale systems were developed and optimization for municipal<br />
wastewater treatment. The MLSS was fur<strong>th</strong>er lowered to 15,000 from 20,000 mg/L while<br />
<strong>th</strong>e SRT remained long to limit sludge production. Developments in <strong>th</strong>e optimization <strong>of</strong><br />
operating conditions has allowed for prolonging membrane life to approximately 5 years.<br />
Process developments included 3-mm pre-screening, increase in membrane and plant size,
optimization <strong>of</strong> <strong>th</strong>e filtration cycle, improvement <strong>of</strong> aerator reliability and improved<br />
cleaning strategies on a rotational basis.<br />
The development <strong>of</strong> membrane module, improved anti-trash screening and cyclic<br />
aeration and standardised design which are <strong>th</strong>e recent advancements. This allowed for <strong>th</strong>e<br />
systems to be handled at peak loads and prolonged membrane life to at least 5 years and<br />
reduced membrane costs.<br />
The first full-scale plant was located in Sou<strong>th</strong> West England, where <strong>th</strong>e MBR was<br />
designed to treat municipal wastewater in a site wi<strong>th</strong> area restrictions and located close to a<br />
be<strong>ac</strong>h and residential area. The plant was able to treat 13,000 m 3 /d and enclosed in a<br />
building 105 m long. The system was effective in removing b<strong>ac</strong>teria and ammonia. The<br />
second plant was built in <strong>th</strong>e open and used for dairy effluent treatment. The plant was<br />
simple in design and unsophisticated yet was able to treat an effluent load <strong>of</strong> 16 ton/d on<br />
BOD and was able to discharge effluent directly into a river. The MBR units were located<br />
in 10 tanks, e<strong>ac</strong>h wi<strong>th</strong> a flow <strong>of</strong> 1,000 m 3 /d <strong>of</strong> screened effluent prior to discharge into an<br />
existing oxidation ditch. Though, initially it had been used for treating domestic<br />
wastewater, later its application widened.<br />
2.11.2 Application <strong>of</strong> Membrane Biore<strong>ac</strong>tors<br />
Bressi and Favari (1997) conducted studies on a MBR system consisting <strong>of</strong> an<br />
<strong>ac</strong>tivated sludge process coupled wi<strong>th</strong> an external hollow fibre ceramic MF unit. The<br />
system was aerated by means <strong>of</strong> diffusers and <strong>th</strong>e mixed liquor passed <strong>th</strong>rough <strong>th</strong>e lumen<br />
<strong>of</strong> membrane and was recycled to <strong>th</strong>e <strong>ac</strong>tivated sludge whilst permeate was extr<strong>ac</strong>ted on<br />
<strong>th</strong>e shell side. The continuous recycle aided in maintaining homogeneous conditions wi<strong>th</strong>in<br />
<strong>th</strong>e aerobic re<strong>ac</strong>tor.<br />
Hall, et al. (1995) investigated <strong>th</strong>e system for removal <strong>of</strong> adsorbable organic halogen<br />
(AOX). It gained 61% AOX removal during <strong>th</strong>e operation at HRT <strong>of</strong> 24 h. It was operated<br />
under condition <strong>of</strong> MLSS from 10,000 to 20,000 mg/L and wi<strong>th</strong> an initial AOX from 21 to<br />
50 mg/L. Lubbecke, et al. (1995) experimented <strong>th</strong>e pilot scale for landfill le<strong>ac</strong>hate<br />
treatment by MBR process. Concentration <strong>of</strong> raw le<strong>ac</strong>hate contains 2,700 to 4,300 mg/L<br />
COD, 200 to 350 mg/L BOD, and 1.5 to 4.4 mg/L AOX. This system was operated at HRT<br />
from 15 to 25 hours and pressure from 2.5 to 4.5 bars. It <strong>ac</strong>hieved 75% to 80% COD<br />
removal and 30% to 60% AOX reduction under <strong>th</strong>e average permeate flux 15 L/m 2 -h for<br />
<strong>th</strong>e NF membrane. While, for an average permeate flux <strong>of</strong> 40 L/m 2 -h for UF membrane, it<br />
could eliminate 65% and 25% to 30% <strong>of</strong> COD and AOX, respectively. Jensen, et al. (2001)<br />
investigated MBR for le<strong>ac</strong>hate treatment. This process was conducted at pH range from 6.5<br />
to 6.8 wi<strong>th</strong> HRT <strong>of</strong> 2.7 days <strong>th</strong>e performance <strong>ac</strong>hieved a COD removal efficiency <strong>of</strong> more<br />
<strong>th</strong>an 90%.<br />
Results from <strong>th</strong>e study indicated <strong>th</strong>at <strong>th</strong>e membrane biore<strong>ac</strong>tor processes have great<br />
potential wi<strong>th</strong> respect to biomass retention and <strong>th</strong>eir treatment efficiency. The study<br />
showed <strong>th</strong>at <strong>th</strong>e incorporation <strong>of</strong> membranes in <strong>th</strong>e system retains <strong>ac</strong>tive biological b<strong>ac</strong>teria<br />
population and produces a high quality effluent. The system also showed <strong>th</strong>at it was<br />
probably capable <strong>of</strong> higher loading rates and has yet to <strong>ac</strong>hieve its maximum treatment<br />
cap<strong>ac</strong>ity. This was made possible wi<strong>th</strong> good control <strong>of</strong> b<strong>ac</strong>teria population in <strong>th</strong>e re<strong>ac</strong>tor<br />
provided by <strong>th</strong>e membranes. Throughout <strong>th</strong>e study, <strong>th</strong>ere was negligible biomass loss<br />
44
<strong>th</strong>rough <strong>th</strong>e effluent. Different operational conditions for <strong>th</strong>e application <strong>of</strong> MBR in<br />
wastewater treatment are presented in Table 2.19.<br />
When <strong>th</strong>e performance <strong>of</strong> MBR was evaluated, <strong>th</strong>e removal efficiencies was found to<br />
be between 78 to 94 % for young le<strong>ac</strong>hate wi<strong>th</strong> COD > 10,000 mg/L, 60 to 65 % for<br />
intermediate le<strong>ac</strong>hate wi<strong>th</strong> COD ranging from 5,000 to 7,000 mg/L and 23 to 46 % in <strong>th</strong>e<br />
case <strong>of</strong> stabilized le<strong>ac</strong>hate wi<strong>th</strong> COD < 2,500 mg/L. However, <strong>th</strong>e membrane biore<strong>ac</strong>tor<br />
alone was not able to treat <strong>th</strong>e pollutant to meet effluent discharge as it was unable to<br />
reduce chlorides, sulphates, ammonia-nitrogen and refr<strong>ac</strong>tory organic compounds.<br />
When combined reverse osmosis-nan<strong>of</strong>iltration system has been operated at a landfill<br />
site in Halle-Lochau, Germany, consistency wi<strong>th</strong> a permeate recovery rate <strong>of</strong> 95 to 97.5 %<br />
could be <strong>ac</strong>hieved. The primary disadvantages <strong>of</strong> membrane biore<strong>ac</strong>tors include capital<br />
costs for <strong>th</strong>e membranes and operating costs associated wi<strong>th</strong> routine membrane cleaning.<br />
However, one <strong>of</strong> <strong>th</strong>e major disadvantages <strong>of</strong> reverse osmosis and membrane<br />
processes is membrane fouling, more especially bi<strong>of</strong>ouling. Bi<strong>of</strong>ouling is a serious<br />
problem for <strong>th</strong>e operation <strong>of</strong> membrane biore<strong>ac</strong>tor systems because it results in decreased<br />
trans-membrane fluxes. Bi<strong>of</strong>ouling involves <strong>th</strong>e combined effects <strong>of</strong> biological, physical,<br />
and chemical clogging <strong>of</strong> membrane pores. Clogged pores result in: (a) reduced transmembrane<br />
fluxes, (b) a need for higher operating pressures, and (c) deterioration <strong>of</strong> <strong>th</strong>e<br />
membrane. To eliminate <strong>th</strong>e problems associated wi<strong>th</strong> bi<strong>of</strong>ouling, it is necessary to study<br />
bi<strong>of</strong>ilm att<strong>ac</strong>hment and formation on membrane surf<strong>ac</strong>es. By understanding <strong>th</strong>e<br />
mechanisms <strong>of</strong> bi<strong>of</strong>ilm formation, <strong>th</strong>e initiation <strong>of</strong> bi<strong>of</strong>ouling formation can be eliminated.<br />
If <strong>th</strong>e initiation <strong>of</strong> bi<strong>of</strong>ouling is eliminated, <strong>th</strong>e costs associated wi<strong>th</strong> cleaning <strong>th</strong>e<br />
membranes could be dramatically reduced.<br />
Membrane biore<strong>ac</strong>tors are fur<strong>th</strong>er able to pre-treat le<strong>ac</strong>hate more successfully <strong>th</strong>an<br />
SBR processes prior to disposal in <strong>th</strong>e sewers. Due to <strong>th</strong>e presence <strong>of</strong> membrane; a<br />
complete retention <strong>of</strong> solids is still possible to maintain. However, membrane systems are<br />
susceptible to shock loading <strong>of</strong> ammonia. When <strong>th</strong>is occurs, biomass may be affected.<br />
2.11.3 Sludge Char<strong>ac</strong>teristics<br />
In <strong>th</strong>e membrane biore<strong>ac</strong>tor (MBR) system, membrane fouling is attributed to <strong>th</strong>e<br />
physico-chemical inter<strong>ac</strong>tion between <strong>th</strong>e bi<strong>of</strong>ilm and membrane. When <strong>th</strong>e bi<strong>of</strong>ilm gets<br />
deposited on <strong>th</strong>e membrane surf<strong>ac</strong>e, <strong>th</strong>is leads to decline in <strong>th</strong>e permeate flux. This cake<br />
layer can be removed from <strong>th</strong>e membrane <strong>th</strong>rough a suitable washing protocol. On <strong>th</strong>e<br />
o<strong>th</strong>er hand, internal fouling caused by <strong>th</strong>e adsorption <strong>of</strong> dissolved matter into <strong>th</strong>e<br />
membrane pores could be generally removed by chemical cleaning.<br />
The phenomenon <strong>of</strong> membrane fouling in <strong>th</strong>e MBR system is very complex and<br />
difficult to understand. The sludge char<strong>ac</strong>teristic is one <strong>of</strong> main f<strong>ac</strong>tors influencing <strong>th</strong>e<br />
membrane fouling which includes mixed liquor suspended solids (MLSS), dissolved<br />
substances, floc size and extr<strong>ac</strong>ellular polymeric substances (EPS). The components <strong>of</strong> <strong>th</strong>e<br />
mixed liquor, ranging from flocculant solids to dissolved polymers such as extr<strong>ac</strong>ellular<br />
polymeric substances (EPS) can lead to membrane fouling.<br />
45
Table 2.19 Operating Conditions <strong>of</strong> Membrane Biore<strong>ac</strong>tor Process for Treatment <strong>of</strong> Different Kinds <strong>of</strong> Wastewater<br />
Wastewater<br />
Industrial<br />
Wastewater<br />
Le<strong>ac</strong>hate<br />
Volume<br />
(L)<br />
HRT<br />
(h)<br />
Initial COD<br />
(mg/L)<br />
46<br />
BOD/COD<br />
MLSS<br />
(mg/L)<br />
SRT<br />
(d)<br />
OLR<br />
(kg COD/m 3 .d)<br />
Reference<br />
5500 30,000-50,000 20,000 50 2.2-10.2 Nagano, et al., 1992<br />
2750 140 42,660<br />
10,900 16 5.40 Krau<strong>th</strong> and Staab,<br />
1993<br />
1900 144-240 29,400 1,800 50-75 2.5-4.9 Zaloum, et al., 1994<br />
- 24 13,300 0.49 - - - Scott and Smi<strong>th</strong>, 1997<br />
15 24 21-50 (AOX) 10,000-20,000 - - Hall, et al., 1995<br />
220 15-25 2,700-4,300 30,000-47,000 Lubbecke, et al., 1995<br />
287 (m 3 ) 54 14,200 28,700 31 6.3 Mishra, et al., 1996<br />
180 (m 3 ) 28.8 4,000 0.2<br />
Dijk and Roncken,<br />
1997<br />
9,500 240 8,000 (BOD) 4,000 30 Ahn, et al., 1999<br />
303 (m 3 ) 65 850-4,200 0.40-0.75 8,000-10,000 80 Jensen, et al., 2001
Mixed Liquor Suspended Solids and Dissolved Substances<br />
The effects <strong>of</strong> <strong>th</strong>e MLSS concentration on <strong>th</strong>e membrane fouling have been reported<br />
by many researchers as membrane resistance varies proportionally in MLSS concentration<br />
(Fane, et al., 1981) and when <strong>th</strong>e MLSS concentration exceeded 40,000 mg/L, <strong>th</strong>e flux is<br />
found <strong>th</strong>at dramatically decrease (Yamamoto, et al., 1989). However, Lubbecke, et al.<br />
(1995) illustrated <strong>th</strong>at MLSS concentrations upto 30,000 mg/L is not directly responsible<br />
for irreversible fouling, and <strong>th</strong>at viscosity and dissolved matter have a more significant<br />
imp<strong>ac</strong>t on flux decline. The increase in viscosity to yield a substantial suction pressure<br />
increase can causes <strong>th</strong>e failure <strong>of</strong> MBR system (Ueda, et al., 1996).<br />
The effects <strong>of</strong> MLSS, dissolved matter, and viscosity on membrane fouling could be<br />
estimated as given by Sato and Ishii (1991) in <strong>th</strong>e following manner:<br />
Where:<br />
0.<br />
926<br />
47<br />
1.<br />
368<br />
0.<br />
326<br />
R = 842 . 7 * ∆P<br />
* ( MLSS)<br />
* ( COD)<br />
* ( µ )<br />
Eq. 2.1<br />
R = Filtration resistance, m -1<br />
∆P = Transmembrane pressure, Pa<br />
µ = Viscosity, Pa.s<br />
MLSS = mixed liquor suspended solid, mg/L<br />
COD = Soluble chemical oxygen demand, mg/L<br />
According to <strong>th</strong>e few researches, <strong>th</strong>e role <strong>of</strong> mixed liquor in membrane fouling was<br />
due to <strong>th</strong>e presence <strong>of</strong> suspended solids (SS), colloids, and dissolved matter which<br />
contributed to resistance against filtration by 65, 30, and 5 % respectively (Derfrance, et al.,<br />
2000). Through fr<strong>ac</strong>tionation <strong>of</strong> <strong>th</strong>e mixed liquor <strong>of</strong> <strong>ac</strong>tivated sludge into floc cell, EPS<br />
and dissolved mater, Chang and Lee (1998) indicated EPS as an important component<br />
contributing to fouling causing resistance in <strong>th</strong>e filtration process. However, <strong>th</strong>ese studies<br />
show <strong>th</strong>at individual fouling resistances were not additive due to <strong>th</strong>e sum <strong>of</strong> <strong>th</strong>e resistances<br />
given by e<strong>ac</strong>h component was found to be greater <strong>th</strong>an <strong>th</strong>e measured total resistance.<br />
Wisniewski and Grasmick (1998) fr<strong>ac</strong>tionated <strong>th</strong>e <strong>ac</strong>tivated sludge suspension into<br />
settleable particles (particle size above 100 µm), supr<strong>ac</strong>olloidal-colloidal fr<strong>ac</strong>tion (nonsettleable<br />
particle wi<strong>th</strong> a size ranging from 0.05 to 100 µm), and soluble fr<strong>ac</strong>tion (obtained<br />
after filtration wi<strong>th</strong> 0.05 µm membrane). They revealed <strong>th</strong>at 52% <strong>of</strong> <strong>th</strong>e total resistance<br />
could be attributed to soluble components.<br />
Particle Size Distribution<br />
Many researchers have sought to establish <strong>th</strong>e influence <strong>of</strong> particle size on <strong>th</strong>e cake<br />
layer resistance. Generally, <strong>th</strong>e particle size <strong>of</strong> an <strong>ac</strong>tivated sludge floc ranges from 1.2 to<br />
600 µm (Jorand, et al., 1995). The break-up <strong>of</strong> biological flocs, generating fine colloids<br />
and cells which later form a denser cake layer on <strong>th</strong>e membrane is due to <strong>th</strong>e shear force<br />
rising as a result <strong>of</strong> pumping during cross-flow filtration (Wisniewski and Grasmick, 1998;<br />
Kim, et al., 2001). According to Wisniewski, et al. (2000), after <strong>th</strong>e floc breakup, <strong>th</strong>e<br />
suspension produced consists mainly <strong>of</strong> particles having a size <strong>of</strong> around 2 µm causing a<br />
decrease in flux. 97% <strong>of</strong> <strong>th</strong>e particles in <strong>th</strong>e MBR system have an average diameter smaller<br />
<strong>th</strong>an 10 µm, while <strong>th</strong>e <strong>ac</strong>tivated sludge contained flocs range from 20 to 200 µm in size<br />
(Cicek, et al., 1999).
Floc breakup exposes <strong>th</strong>e EPS present inside <strong>th</strong>e floc structure as well as increasing<br />
<strong>th</strong>e EPS level in bulk solution, which causing seriously membrane fouling (Chang and Lee,<br />
2001). The floc breakup also leads to a loss <strong>of</strong> biological <strong>ac</strong>tivity (Brockmann and<br />
Seyfried, 1996; Ghyoot, et al., 1999; Chang and Lee, 2001), change in microorganism<br />
population (Rosenberg, et al., 1999) and decreasing settleability (Cicek, et al., 1999).<br />
Extr<strong>ac</strong>ellular Polymeric Substances (EPS)<br />
The EPS production is a general property <strong>of</strong> microorganisms in natural environments<br />
and occurs in b<strong>ac</strong>teria, algae, yeast, and fungi (Flemming and Wingender, 2001). They are<br />
construction materials for microbial aggregates such as bi<strong>of</strong>ilm, floc, and sludge.<br />
An <strong>ac</strong>tivated sludge floc is a microbial entity which is formed by different species<br />
<strong>of</strong> biomass. The components <strong>of</strong> <strong>th</strong>e floc are embedded in a polymeric network <strong>of</strong> EPS. A<br />
significant barrier to permeate flow in <strong>th</strong>e MBR is due to EPS providing a highly hydrated<br />
gel matrix in which microorganisms are embedded. Microbial EPS are high molecularweight<br />
mucous secretions from microbial cells. They are important for floc formation in<br />
<strong>ac</strong>tivated sludge liquors (Sanin and Vesilind, 2000; Liao, et al., 2001). The EPS matrix is<br />
very heterogeneous, wi<strong>th</strong> polymeric materials which includes polys<strong>ac</strong>charides, proteins,<br />
lipids, and nucleic <strong>ac</strong>ids (Bura, et al., 1998; Nielson and Jahn, 1999)<br />
Many MBR studies have identified EPS as <strong>th</strong>e most significant biological f<strong>ac</strong>tor<br />
responsible for membrane fouling. Chang and Lee (1998) found <strong>th</strong>ere to be a linear<br />
relationship between membrane fouling and EPS levels. Nagaoka, et al. (1996, 1999)<br />
found <strong>th</strong>at increase in hydraulic resistance and viscosity <strong>of</strong> <strong>th</strong>e mixed liquor was due to <strong>th</strong>e<br />
<strong>ac</strong>cumulated EPS in <strong>th</strong>e system and also on <strong>th</strong>e membrane. There was a linear relationship<br />
between <strong>th</strong>e hydraulic resistance and viscosity <strong>of</strong> <strong>th</strong>e mixed liquor, which caused rapid<br />
att<strong>ac</strong>hment <strong>of</strong> <strong>th</strong>e suspended EPS. Huang, et al. (2001) found soluble organic substances<br />
wi<strong>th</strong> high molecular weights, mostly attributable to metabolic products, to <strong>ac</strong>cumulate in<br />
<strong>th</strong>e biore<strong>ac</strong>tor. These had an indirect proportionality wi<strong>th</strong> <strong>th</strong>e membrane permeability.<br />
Accumulation <strong>of</strong> 50 mgTOC/L resulted in 70% decrease in flux. The fouling proneness<br />
due to specific EPS components has also been studied. Shin, et al. (1999) ascribed 90% <strong>of</strong><br />
<strong>th</strong>e cake resistance to EPS and found resistance varied wi<strong>th</strong> <strong>th</strong>e ratio <strong>of</strong> carbohydrate and<br />
protein in <strong>th</strong>e EPS, <strong>th</strong>ereby influencing permeated flux during ultrafiltration. The permeate<br />
flux decreased wi<strong>th</strong> an increasing protein content (Mukai, et al., 2000). Kim, et al. (1998)<br />
found <strong>th</strong>at <strong>th</strong>e addition <strong>of</strong> powdered <strong>ac</strong>tivated carbon to <strong>th</strong>e MBR was shown to increase<br />
permeability by reducing dissolved EPS levels from 121-196 mg/gVSS to 90-127<br />
mg/gVSS.<br />
Most studies on <strong>th</strong>e effect <strong>of</strong> EPS on membrane fouling rely on EPS extr<strong>ac</strong>tion from<br />
<strong>th</strong>e sludge flocs. However, relatively large amounts <strong>of</strong> EPS can originate from<br />
unmetabolized wastewater components and b<strong>ac</strong>terial products arising ei<strong>th</strong>er from cell-lysis<br />
<strong>of</strong> cell-structural polymeric components (Dign<strong>ac</strong>, et al., 1998). Thus, <strong>th</strong>e quantitative<br />
expression <strong>of</strong> flux as a function <strong>of</strong> EPS concentration has an inherent limitation.<br />
48
2.12 Yeasts<br />
2.12.1 Introduction<br />
The yeast degrade organics ei<strong>th</strong>er anaerobically (fermentation) or aerobically<br />
(oxidation). The most typical yeast process applied in food or beverage industries is<br />
anaerobic, also known as alcoholic fermentation. The end products <strong>of</strong> fermentation can be<br />
alcohols, <strong>ac</strong>ids, esters, glycerol and aldehydes. A typical re<strong>ac</strong>tion <strong>of</strong> sugar fermentation by<br />
yeasts is shown in <strong>th</strong>e following re<strong>ac</strong>tion:<br />
C6H12O6 + nutrients C2H5OH + CO2 + new biomass<br />
Under aerobic process, complete oxidation <strong>of</strong> organics yields carbon dioxide and<br />
water. Abundant supply <strong>of</strong> oxygen enhances considerable yeast grow<strong>th</strong>; whereas<br />
incomplete oxidation is <strong>ac</strong>companied by <strong>th</strong>e <strong>ac</strong>cumulation <strong>of</strong> <strong>ac</strong>ids and o<strong>th</strong>er intermediary<br />
products. There are differences in <strong>th</strong>e compounds which can be assimilated by various<br />
species <strong>of</strong> yeasts. Some can degrade pentoses, polys<strong>ac</strong>charides (starch), sugars, alcohols,<br />
organic <strong>ac</strong>ids (l<strong>ac</strong>tic, <strong>ac</strong>etic, citric) and o<strong>th</strong>er organic substrates.<br />
COHNS + O2 + nutrients CO2 + H2O + new biomass + end products<br />
(Organic matter)<br />
Yeasts may utilize <strong>th</strong>e nitrogen required in <strong>th</strong>eir metabolism for <strong>th</strong>e syn<strong>th</strong>esis <strong>of</strong><br />
protein from organic (amino <strong>ac</strong>ids, urea, vitamins, peptone, aliphatic amines, etc.) and<br />
inorganic sources (ammonia, nitrite and nitrate). Most species can utilize <strong>th</strong>e ammonium<br />
ionmaking it appropriate for le<strong>ac</strong>hate treatment. O<strong>th</strong>er nutrients required for yeast grow<strong>th</strong><br />
include phosphorous, sulfur (organic sulfur and sulphate), minerals (potassium, magnesium,<br />
sodium and calcium). The C:N:P ratio <strong>of</strong> Candida utilis biomass was found to be 100:20:5.<br />
Therefore, nutrient demands <strong>of</strong> yeasts are higher <strong>th</strong>an <strong>th</strong>at <strong>of</strong> b<strong>ac</strong>teria whose BOD5:N:P<br />
ratio is 100:5:1 (Defrance, 1993).<br />
Yeasts can grow in a wide pH range (from 2.2 to 8.0). In general, yeasts grow well<br />
on media wi<strong>th</strong> <strong>ac</strong>id re<strong>ac</strong>tions (from 3.8 to 4.0), whereas optimum pH values for b<strong>ac</strong>teria<br />
grow<strong>th</strong> range from 7.5 to 8.5. Yeasts have been used in <strong>th</strong>e fermentation industry which<br />
requiring operation at a high substrate concentrations and under high loads. It is noted <strong>th</strong>at<br />
yeast can be utilized to treat <strong>th</strong>e wastewater containing solids, high concentrations <strong>of</strong><br />
organic matter and salt, and o<strong>th</strong>er substances, which are difficult to treat using <strong>ac</strong>tivated<br />
sludge process (Nishihara ESRC Ltd., 2001). Fur<strong>th</strong>ermore, yeasts can grow in<br />
temperatures ranging from 0 to 47 o C, <strong>th</strong>e optimum temperature being from 20 to 30 o C.<br />
2.12.2 Applications <strong>of</strong> Yeasts for Wastewater Treatment<br />
Miskiewicz, et al. (1982) developed yeast based treatment for fresh piggery wastes<br />
by adding carbon source (beet molasses or sucrose). Candida tropicalis, Candida<br />
tropicalis, Candida robusta and Candida utilis were <strong>th</strong>e yeast strains <strong>th</strong>at were cultured in<br />
<strong>th</strong>e aerated batch re<strong>ac</strong>tor. According to <strong>th</strong>e study, molasses are <strong>th</strong>e most appropriate carbon<br />
source <strong>of</strong> yeast. The use <strong>of</strong> raw piggery waste wi<strong>th</strong>out carbon supplement leads to low<br />
biomass yield and low treatment efficiency, inspite <strong>of</strong> nutrients (N, P) content being high.<br />
The culture <strong>of</strong> C. utilis on molasses-enriched piggery waste (5,570 mg COD/L) could<br />
49
obtain high treatment efficiencies <strong>of</strong> 76% TKN, 60% COD, 84% phosprorus removal at<br />
HRT <strong>of</strong> 7 hours and wi<strong>th</strong> a F/M ratio <strong>of</strong> 1.73 g COD/g MLSS.d. The maximum specific<br />
grow<strong>th</strong> rate <strong>of</strong> C. utilis was found to be 0.19 h -1<br />
Hu (1989) used ten different yeast strains in cultures to treat vermicelli wastewater<br />
which contained BOD ranging from 24,000 to 44,000 mg/L and high concentration <strong>of</strong><br />
starch, l<strong>ac</strong>tic <strong>ac</strong>id and protein. Based on <strong>th</strong>e ability <strong>of</strong> starch degradation, protein<br />
hydrolysis and l<strong>ac</strong>tic <strong>ac</strong>id tolerance, <strong>th</strong>ese yeast strains were screened from 391 colonies<br />
isolated from soil samples. Most <strong>of</strong> <strong>th</strong>em could grow well wi<strong>th</strong> pH range <strong>of</strong> 3.0-5.0, 4.0<br />
being <strong>th</strong>e optimum. The results shows <strong>th</strong>at <strong>th</strong>e two strains could reduce soluble COD by<br />
92% at HRT <strong>of</strong> 7 days, F/M ratio <strong>of</strong> 0.48 g COD/g MLSS.d and VLR <strong>of</strong> 1.03 kg<br />
COD/m 3 .d. Due to <strong>th</strong>e poor settling ability <strong>of</strong> yeasts, <strong>th</strong>ey could not be flocculated or<br />
settled as in a conventional <strong>ac</strong>tivated sludge process and were easily washed out wi<strong>th</strong> <strong>th</strong>e<br />
effluent. Therefore, <strong>th</strong>e HRT in <strong>th</strong>is process have to keep long and same as <strong>th</strong>e SRT. The<br />
au<strong>th</strong>or postulated <strong>th</strong>at <strong>th</strong>e fungi contamination prevented <strong>th</strong>e formation <strong>of</strong> yeast flocs.<br />
Chigusa, et al. (1996) used nine different strains <strong>of</strong> yeasts capable <strong>of</strong> decomposing<br />
<strong>th</strong>e oil to treat wastewater from oil manuf<strong>ac</strong>turing plants. A pilot scale yeast treatment<br />
system had been run for one year. According to <strong>th</strong>e results, 10,000 mg/L <strong>of</strong> hexane extr<strong>ac</strong>ts<br />
in <strong>th</strong>e raw wastewater were reduced by <strong>th</strong>e yeast mixture to about 100 mg/L.<br />
Elmaleh et al.(1996) investigated <strong>th</strong>e yeast treatment <strong>of</strong> highly concentrated <strong>ac</strong>idic<br />
wastewater from <strong>th</strong>e food processing industry. The strain Candida utilis was cultured in<br />
continuously completed mixed re<strong>ac</strong>tors. This system did not have a separate settling tank;<br />
<strong>th</strong>e SRT and HRT <strong>of</strong> <strong>th</strong>e system were identical. A mixture <strong>of</strong> <strong>ac</strong>etic <strong>ac</strong>id, propionic and<br />
butyric <strong>ac</strong>id was <strong>th</strong>e carbon source <strong>of</strong> feed wastewater. The pH was maintained at 3.5 to<br />
prevent any b<strong>ac</strong>terial contamination. The TOC removal obtained was 97% at high loading<br />
rates (30 kg TOC/m 3 .d). The grow<strong>th</strong> yield and maximum specific grow<strong>th</strong> rate <strong>of</strong> yeasts<br />
were similar to <strong>th</strong>ose for conventional <strong>ac</strong>tivated sludge (µmax = 0.5 h - ; Y = 0.85-1.05 kg<br />
SS/kg TOC for <strong>ac</strong>etic <strong>ac</strong>id).<br />
Olive mill wastewater normally contains high concentration <strong>of</strong> fats, sugars, phenols,<br />
volatile fatty <strong>ac</strong>ids which contribute to a very high COD concentration (100,000-200,000<br />
mg/L). Scioli and Vollaro (1997) reported <strong>th</strong>at Yarrowia lipolytica cultured in aerated<br />
fermenter was capable <strong>of</strong> reducing <strong>th</strong>e COD level <strong>of</strong> olive oil processing wastewater by<br />
80% in 24 h. Fats and sugars were completely assimilated while me<strong>th</strong>anol and e<strong>th</strong>anol<br />
were present. The effluent had a pleasant smell due to <strong>th</strong>e presence <strong>of</strong> <strong>th</strong>ese compounds.<br />
The au<strong>th</strong>ors asserted <strong>th</strong>at a possible appro<strong>ac</strong>h for pollution reduction in olive-oil-producing<br />
countries is to use membrane to filter effluent before discharging into <strong>th</strong>e sewage system.<br />
Useful biomass (40% protein) and valuable lipase enzyme could also be obtained in <strong>th</strong>is<br />
process.<br />
Arnold, et al. (2000) investigated <strong>th</strong>e ability <strong>of</strong> selected yeast strains (C. utilis and<br />
Gal<strong>ac</strong>tomyces geotrichum) to purify silage wastewater containing high COD concentration<br />
<strong>of</strong> 30,000 to 80,000 mg/L by using <strong>th</strong>e shaker-flask. High removal efficiencies <strong>of</strong> COD<br />
(74-95%), VFA (85-99%) and phosphate (82-99%) were obtained after 24 hrs and some<br />
ammonia was also removed. During treatment, pH rose from initial values <strong>of</strong> 3.7-5.8 to<br />
8.5-9.0. This was presumably due to removal <strong>of</strong> l<strong>ac</strong>tic <strong>ac</strong>id and VFAs. An efficient<br />
removal <strong>of</strong> P from <strong>th</strong>e system could lead to <strong>th</strong>e shortage <strong>of</strong> phosphorus.<br />
50
Nishihara ESRC Ltd. (2001) studied <strong>th</strong>e effect <strong>of</strong> <strong>th</strong>e Yeast Cycle System on dried<br />
food and marine products processing wastewater. In <strong>th</strong>is system, <strong>th</strong>e yeast<br />
treatment/pretreatment could be conducted wi<strong>th</strong> high organic and nutrient loadings. The<br />
organic removal obtained was more <strong>th</strong>an 90%. Moreover, <strong>th</strong>is system is relatively<br />
unaffected by load variation and <strong>th</strong>e structure <strong>of</strong> yeast flocs f<strong>ac</strong>ilitated oxygen diffusion.<br />
Table 2.20 gives a comparison wi<strong>th</strong> conventional complete mixing <strong>ac</strong>tivated sludge in<br />
terms <strong>of</strong> <strong>th</strong>e operating conditions. Dried food products processing wastewater has BOD5<br />
concentrations ranging from 2,920-15,800 mg/L and SS concentration 1,360 mg/L. Marine<br />
products processing wastewater has BOD5 and SS concentrations ranging from 3,550-<br />
8,850 mg/L and 680-940 mg/L respectively. Some yeast strains, Candida edax, Candida<br />
valdivana and Candida emobii, were predominantly grown during enrichment wi<strong>th</strong> <strong>th</strong>is<br />
raw wastewater. The predominance <strong>of</strong> yeast strains wi<strong>th</strong> <strong>th</strong>e enrichment culture technique<br />
is based on free competition among different organisms in real wastewater. It was found<br />
<strong>th</strong>at <strong>th</strong>e yeast treatment process can obtain high efficiency at a higher volumetric loading<br />
(5–6 times), F/M ratio (2–3 times) when compared wi<strong>th</strong> <strong>th</strong>e AS process. The efficiency <strong>of</strong><br />
<strong>th</strong>is system is presented in Table 2.21.<br />
Table 2.20 Operating Conditions <strong>of</strong> Yeast System Compared wi<strong>th</strong> Activated Sludge<br />
Process (Nishihara ESRC Ltd., 2001)<br />
Parameter Unit Dried Food Marine Activated<br />
Products Products Sludge*<br />
Influent BOD5<br />
BOD5 volumetric<br />
loading<br />
mg/L<br />
kg/m<br />
5,200 5,450 110-400<br />
3 .day 9.12 8.48 0.8 – 1.9<br />
Yeast concentration mg/L 8,000-13,500 8,000-<br />
10,000<br />
2,500 – 4,000<br />
BOD5 sludge loading kgBOD5 0.9 0.9 0.2 – 0.6<br />
(F/M)<br />
/kgVSS.day<br />
Water temperature °C 27 26 23 – 30<br />
pH 6.5 4.8 6.5 – 8.5<br />
DO mg/L 0.8 0.7 ≥ 2<br />
SVI ml/g 53 66 100 – 120<br />
Remark * Complete mixed <strong>ac</strong>tivated sludge (Tchobanoglous and Burton, 1991)<br />
Table 2.21 Performance <strong>of</strong> Yeast Based Treatment System in Dried Food Products and<br />
Marine Product Industry (Nishihara ESRC Ltd., 2001)<br />
Parameter (mg/L)<br />
Dried Food Products Marine Products<br />
BOD5 SS T-N T-P Cl -<br />
BOD5 SS T-N T-P Cl -<br />
Influent<br />
After pretreatment<br />
5,450 798 153 33 5,160 5,218 1,360 198 38 1,080<br />
by yeast 150 113 72 18 5,080 118 95 109 22 1,068<br />
Efficiency (%)<br />
After <strong>ac</strong>tivated<br />
97 86 53 46 2 98 93 45 42 1<br />
sludge 4 15 10 15 5,080 12 18 16 7 1,068<br />
Efficiency (%) 97 87 86 17 - 90 81 85 68 -<br />
51
Dan, et al. (2002) conducted <strong>th</strong>e high salinity wastewater wi<strong>th</strong> yeast membrane<br />
biore<strong>ac</strong>tor. The COD removal efficiency obtained was from 60% to 85% wi<strong>th</strong> a volumetric<br />
loading rate <strong>of</strong> 3.4 to 16.3 kg COD/m 3 .d. It was found <strong>th</strong>at yeast cell size, low operating<br />
pH, and poor adhesion cap<strong>ac</strong>ity reduced membrane fouling. To reduce <strong>th</strong>e problems <strong>of</strong><br />
frequent membrane fouling, <strong>th</strong>e application <strong>of</strong> yeast to treat wastewater is considered.<br />
2.13 Rationale for <strong>th</strong>e Study and Proposed Treatment Sequence<br />
2.13.1 Le<strong>ac</strong>hate Char<strong>ac</strong>teristic<br />
The development <strong>of</strong> a treatment sequence incorporating biological and physicochemical<br />
processes is necessary for <strong>th</strong>e treatment <strong>of</strong> medium-age or intermediate landfill<br />
le<strong>ac</strong>hate. In <strong>th</strong>e proposed study, le<strong>ac</strong>hate obtained from a sanitary landfill in Pa<strong>th</strong>um<strong>th</strong>ani,<br />
Thailand which has been in operation for 5 years, toge<strong>th</strong>er wi<strong>th</strong> le<strong>ac</strong>hate derived from<br />
compression <strong>of</strong> fresh domestic waste from a transfer station in Bangkok, Thailand were<br />
mixed to simulate a medium-age le<strong>ac</strong>hate.<br />
The le<strong>ac</strong>hate was simulated to mimic a low biodegradable, high ammonia le<strong>ac</strong>hate<br />
wi<strong>th</strong> BOD, COD and TKN ranging from 2,500±500, 8,000±1,000 and 1,900±100 mg/L,<br />
respectively.<br />
The decision to syn<strong>th</strong>esize a le<strong>ac</strong>hate by combining <strong>th</strong>e two le<strong>ac</strong>hate sources was to<br />
attain consistent char<strong>ac</strong>teristic was based on <strong>th</strong>e continual variability <strong>of</strong> le<strong>ac</strong>hate obtained<br />
from a single source. Hence, little or no control <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate can be exercised in<br />
development <strong>of</strong> a treatment sequence making it more complicated. Since, it has been<br />
proposed by previous researchers <strong>th</strong>at some degree <strong>of</strong> control should be maintained over<br />
<strong>th</strong>e waste dumped and le<strong>ac</strong>hate generated, a syn<strong>th</strong>etic le<strong>ac</strong>hate is justified. Fur<strong>th</strong>er,<br />
Thailand’s tropical climate drastically affects <strong>th</strong>e le<strong>ac</strong>hate quality. Therefore, over a longterm<br />
experimental investigation, it is deemed unfeasible to attempt to use a raw le<strong>ac</strong>hate<br />
source.<br />
2.13.2 Need for Ammonia Stripping<br />
Due to <strong>th</strong>e presence <strong>of</strong> elevated ammonia concentrations in <strong>th</strong>e le<strong>ac</strong>hate, sludge<br />
properties are affected resulting in a fine floc which is difficult to settle. The high<br />
ammonium concentration also poses toxicity to <strong>th</strong>e microorganisms, <strong>th</strong>us affecting <strong>th</strong>e<br />
degradation process. Therefore, <strong>th</strong>e effect <strong>of</strong> ammonia concentrations <strong>of</strong> 2,000 mg/L was<br />
investigated wi<strong>th</strong> yeast and b<strong>ac</strong>terial cultures. Due to toxicity, removal <strong>of</strong> ammonia was<br />
<strong>th</strong>erefore apparent for le<strong>ac</strong>hate treatment. Thus, ammonia stripping was evaluated.<br />
Ammonia removal by air stripping was selected as a pre-treatment for <strong>th</strong>e reduction<br />
<strong>of</strong> ammonia from 2,000 to 200 mg/L. Ammonia stripping has <strong>th</strong>e advantage <strong>of</strong> reducing<br />
refr<strong>ac</strong>tory compounds and <strong>th</strong>ereby reducing COD concentrations, by precipitation when<br />
pH is adjusted. This appro<strong>ac</strong>h was adopted in <strong>th</strong>e conventional biological nitrificationdenitrification<br />
process since nitrification-denitrification processes were subjected to many<br />
operation problems such as nitrification-denitrification inhibition.<br />
Fur<strong>th</strong>er, for <strong>th</strong>e le<strong>ac</strong>hate char<strong>ac</strong>teristic, treatment efficiency by nitrificationdenitrification<br />
is considered poor wi<strong>th</strong> BOD/TKN < 2.5, BOD/NH3 < 4 and COD/TKN < 5<br />
(Grady, et al., 1999). In order to ensure successful removal <strong>of</strong> ammonia in <strong>th</strong>e<br />
52
nitrification-denitrification process, an external carbon source in <strong>th</strong>e form <strong>of</strong> le<strong>ac</strong>hate,<br />
me<strong>th</strong>anol etc. could be necessary. An external carbon source could fur<strong>th</strong>er increase <strong>th</strong>e<br />
operational costs. Chemical treatment by coagulation, flocculation and precipitation<br />
eliminates <strong>th</strong>e increased chemical costs making <strong>th</strong>is option realistic for ammonia removal.<br />
Thus, ammonia stripping seems to be <strong>th</strong>e most viable option. While ammonia stripping can<br />
be conducted in p<strong>ac</strong>ked towers wi<strong>th</strong> efficiencies up to 95 %, <strong>th</strong>e intention <strong>of</strong> <strong>th</strong>is study is to<br />
merely reduce le<strong>ac</strong>hate wi<strong>th</strong> total nitrogen content <strong>of</strong> 1,800-2,000 mg/L to a level below<br />
toxicity for fur<strong>th</strong>er biological treatment, for which a conventional ammonia stripping<br />
would be sufficient. Thus, by maintaining an optimal operating condition by controlling,<br />
air flowrate and pH, an ideal condition based on ammonia removal, ammonia toxicity and<br />
mixing power efficiency could be obtained using a conventional stirred tank.<br />
One <strong>of</strong> <strong>th</strong>e main disadvantages <strong>of</strong> ammonia stripping is <strong>th</strong>e high cost associated wi<strong>th</strong><br />
pH adjusters. The choice <strong>of</strong> pH adjuster is also crucial in design and rendering <strong>th</strong>e process<br />
cost effective, a reduction in <strong>th</strong>e amount <strong>of</strong> adjuster can be brought about by pre-aerating<br />
<strong>th</strong>e le<strong>ac</strong>hate. The syn<strong>th</strong>etic le<strong>ac</strong>hate used in <strong>th</strong>is study has an average pH <strong>of</strong> 8.5 ±0.5. Since,<br />
<strong>th</strong>is is already in <strong>th</strong>e alkaline range; <strong>th</strong>e amount <strong>of</strong> buffer added to raise pH for ammonia<br />
stripping is not significant.<br />
2.13.3 Need for Membrane Biore<strong>ac</strong>tors<br />
If <strong>th</strong>e pre-treatment <strong>of</strong> ammonia stripping fails, <strong>th</strong>is would lead to shock loading in<br />
<strong>th</strong>e biological system, making it difficult for <strong>th</strong>e floc to settle down. This problem can be<br />
solved by <strong>th</strong>e adoption <strong>of</strong> a membrane process to repl<strong>ac</strong>e <strong>th</strong>e clarifier in a normal <strong>ac</strong>tivated<br />
sludge process since <strong>th</strong>e membranes can retain total solids until <strong>th</strong>e sludge recovers from<br />
shock loading <strong>of</strong> ammonia.<br />
Purification <strong>of</strong> le<strong>ac</strong>hate by membrane processes aids in preventing fur<strong>th</strong>er<br />
contamination <strong>of</strong> groundwater resources and surf<strong>ac</strong>e water. However, in selecting a<br />
treatment option, or a combination <strong>of</strong> treatment operations, <strong>th</strong>e economic feasibility and<br />
affordability <strong>of</strong> <strong>th</strong>e technology should also be considered. In <strong>th</strong>is regard, membrane<br />
filtration has proven to be a justifiable and economic solution in most cases, even when <strong>th</strong>e<br />
overall costs for <strong>th</strong>e purification are compared wi<strong>th</strong> o<strong>th</strong>er appro<strong>ac</strong>hes for le<strong>ac</strong>hate treatment<br />
(Peters, 1997).<br />
By coupling <strong>of</strong> a membrane wi<strong>th</strong> <strong>th</strong>e <strong>ac</strong>tivated sludge re<strong>ac</strong>tor, a membrane biore<strong>ac</strong>tor<br />
emerges as a logical treatment option. The reduced operational costs associated wi<strong>th</strong><br />
immersed membrane biore<strong>ac</strong>tors proves advantageous in its application and <strong>th</strong>erefore<br />
preferred in <strong>th</strong>e present study.<br />
The use <strong>of</strong> a MBR allows <strong>th</strong>e HRT to be reduced from 1 to 10 days (Qasim and<br />
Chiang, 1994) to less <strong>th</strong>an 24 h. This reduction is drastic and viable in terms <strong>of</strong> operation<br />
costs and effectiveness. Reduction in SRT from conventional <strong>ac</strong>tivated sludge SRT <strong>of</strong> 15<br />
to 60 d has <strong>th</strong>e advantage <strong>of</strong> reducing air requirements in <strong>th</strong>e MBR. Maintaining a lower<br />
MLSS is advantageous since lower <strong>th</strong>e sludge produced, <strong>th</strong>e greater is <strong>th</strong>e effectiveness <strong>of</strong><br />
aeration. This appro<strong>ac</strong>h effectively reduces <strong>th</strong>e aeration requirements and a smaller SRT<br />
and HRT reduces <strong>th</strong>e required re<strong>ac</strong>tor volume and <strong>th</strong>us <strong>th</strong>e capital cost.<br />
53
3.1 Introduction<br />
Chapter 3<br />
Me<strong>th</strong>odology<br />
The present study on landfill le<strong>ac</strong>hate treatment comprises <strong>of</strong> four experimental<br />
stages, namely: toxicity study, ammonia stripping, membrane biore<strong>ac</strong>tor study and sludge<br />
char<strong>ac</strong>terization. The different experimental stages <strong>of</strong> <strong>th</strong>is study are shown in <strong>th</strong>e Figure<br />
3.1.<br />
MBR process<br />
HRT Sludge char<strong>ac</strong>teristics<br />
Figure 3.1 Flowchart Showing Different Stages <strong>of</strong> Experimental Study<br />
3.2 Le<strong>ac</strong>hate Char<strong>ac</strong>terization<br />
Acclimatized yeast and<br />
b<strong>ac</strong>teria sludges<br />
Toxicity study<br />
Ammonia stripping<br />
study<br />
Membrane biore<strong>ac</strong>tor<br />
study<br />
MWCO<br />
The le<strong>ac</strong>hate used for <strong>th</strong>e treatment was obtained from Pa<strong>th</strong>um<strong>th</strong>ani Landfill Site and<br />
Ram-Indra Transfer Station, which were initially char<strong>ac</strong>terized. After char<strong>ac</strong>terization<br />
<strong>th</strong>ese le<strong>ac</strong>hates were mixed in an appropriate proportion to simulate a medium-aged<br />
le<strong>ac</strong>hate composition. The char<strong>ac</strong>teristic <strong>of</strong> <strong>th</strong>e simulated le<strong>ac</strong>hate used for <strong>th</strong>e study is<br />
shown in Table 3.1.<br />
54<br />
Ammonia nitrogen<br />
Lead<br />
pH<br />
Gradient velocity<br />
Cont<strong>ac</strong>t time<br />
Coupling ammonia stripping<br />
wi<strong>th</strong> MBR process<br />
Sludge char<strong>ac</strong>teristics<br />
MWCO
Table 3.1 Composition <strong>of</strong> Simulated Le<strong>ac</strong>hate<br />
Parameters Concentration<br />
pH<br />
7.8-8.2<br />
COD (mg/L)<br />
8,000±1,000<br />
BOD/COD<br />
0.40±0.05<br />
NH4-N (mg/L)<br />
1,700±100<br />
TKN (mg/L)<br />
1,900±100<br />
TDS (mg/L)<br />
12,000±1,000<br />
Note: Pb concentration is below 0.3 mg/L, which has no effect on microbial toxicity.<br />
3.3 Seed Study<br />
3.3.1 Yeast and B<strong>ac</strong>terial Sludge<br />
a) Yeast Sludge<br />
The mixed yeast sludge comprises <strong>of</strong> a mixture <strong>of</strong> wild yeast varieties <strong>th</strong>at exist in<br />
<strong>th</strong>e raw wastewater and which quantitatively propagate under normal enrichment<br />
conditions. The procedure for enrichment <strong>of</strong> yeasts was carried out <strong>ac</strong>cording to <strong>th</strong>e<br />
Standard Me<strong>th</strong>ods for <strong>th</strong>e examination <strong>of</strong> water and wastewater (APHA, et al., 1998). The<br />
yeast strains were selected based on competition among different organisms present in<br />
wastewater (Nishihara Ltd., 2001) by <strong>th</strong>e enrichment culture technique. Figure 3.2<br />
illustrates <strong>th</strong>e procedure for enrichment <strong>of</strong> yeast.<br />
Seed Seed yeast yeast sludge sludge<br />
(from (from sediments sediments) )<br />
Filling<br />
Aeration Aeration 24 24 h h<br />
MLSS<br />
Completion Enriched Completion Enriched culture<br />
> 3,000 mg/L<br />
Figure 3.2 Diagram Illustrating <strong>th</strong>e Enrichment Procedure<br />
55<br />
< 3,000 mg/L<br />
Drawing<br />
Settling
The yeast sludge was collected from <strong>th</strong>e bottom sediments <strong>of</strong> a pond from <strong>th</strong>e<br />
Non<strong>th</strong>aburi landfill site, Thailand. A two-liter container was used for enrichment and was<br />
done using fill-and-draw process. The wastewater feed (having glucose as substrate) was<br />
mixed wi<strong>th</strong> a diffused aeration system. The pH was adjusted to 3.5 which is optimum for<br />
yeast grow<strong>th</strong> and can prevent b<strong>ac</strong>terial contamination (Elmaleh, et al., 1996). After 24<br />
hours <strong>of</strong> aeration, <strong>th</strong>e biomass suspension was allowed to settle for 10 hours. Yeast cells,<br />
normally, settle in <strong>th</strong>e bottom, whereas <strong>th</strong>e <strong>ac</strong>id-tolerant b<strong>ac</strong>teria and filamentous fungi<br />
would remain in <strong>th</strong>e suspension. The b<strong>ac</strong>teria and fungi present in <strong>th</strong>e supernatant were<br />
removed by decanting <strong>th</strong>e supernatant. Around 1.5 liters <strong>of</strong> supernatant was decanted and<br />
fresh medium was added to <strong>th</strong>e next batch. When MLSS <strong>of</strong> <strong>th</strong>e yeast biomass exceeded<br />
3,000 mg/L, <strong>th</strong>e enrichment process was <strong>ac</strong>complished.<br />
b) B<strong>ac</strong>teria Sludge<br />
The b<strong>ac</strong>terial seed sludge was collected from <strong>th</strong>e aeration tank in <strong>th</strong>e <strong>ac</strong>tivated sludge<br />
process <strong>of</strong> a wastewater treatment plant.<br />
3.3.2 Acclimatization<br />
Acclimatization was done in order to obtain a mixed b<strong>ac</strong>terial and yeast culture<br />
which can tolerate le<strong>ac</strong>hate containing low biodegradable organics and high ammonia<br />
concentration. Five-liter batch re<strong>ac</strong>tors were used for <strong>ac</strong>climatization <strong>th</strong>rough fill-and-draw<br />
process. The operating conditions for <strong>th</strong>e re<strong>ac</strong>tors are summarized in Table 3.2.<br />
Table 3.2 Operating Conditions for Yeast and B<strong>ac</strong>teria Acclimatization<br />
Operating Conditions Yeast Re<strong>ac</strong>tor B<strong>ac</strong>teria Re<strong>ac</strong>tor<br />
HRT (h) 24 24<br />
MLSS (mg/L) 10,000 5,000<br />
COD (mg/L) 8,000±1,000 8,000±1,000<br />
Temperature ( O C) 25 to 30 25 to 30<br />
pH 3.5 to 3.8 6.8 to 7.0<br />
Bo<strong>th</strong> <strong>th</strong>e re<strong>ac</strong>tors were aerated by a diffused aeration system and <strong>th</strong>e pH was adjusted<br />
to 3.5 - 3.8 for yeast grow<strong>th</strong> and 6.8 - 7.0 for b<strong>ac</strong>terial grow<strong>th</strong>, respectively. After 24 hours<br />
<strong>of</strong> aeration, <strong>th</strong>e biomass was allowed to settle for 3 hours. After 3 hours <strong>of</strong> settlement, <strong>th</strong>e<br />
supernatant was collected and centrifuged at 4000 rpm for 15 minutes. The experiment was<br />
repeated for <strong>th</strong>e next batch under <strong>th</strong>e same conditions until a COD removal <strong>of</strong> 70% could<br />
be <strong>ac</strong>hieved. Once <strong>th</strong>e COD removal efficiency re<strong>ac</strong>hed a value greater <strong>th</strong>an 70%, <strong>th</strong>e<br />
<strong>ac</strong>climatization was presumed to be complete.<br />
3.4 Toxicity Studies<br />
The toxicity studies were done wi<strong>th</strong> yeast and b<strong>ac</strong>terial culture. The toxicity <strong>of</strong> <strong>th</strong>e<br />
culture was tested for different concentrations <strong>of</strong> ammonia and lead.<br />
56
3.4.1 Ammonia Toxicity<br />
The experiments were conducted in a closed 0.9-liter batch respirometer equipped<br />
wi<strong>th</strong> a recorder, DO meter, and water j<strong>ac</strong>ket vessel to maintain a constant temperature as<br />
shown in Figure 3.3.<br />
2<br />
7<br />
Figure 3.3 Respirometer<br />
The operating conditions for yeast and b<strong>ac</strong>terial culture used in <strong>th</strong>is experiment are<br />
given in Table 3.3. The experiment was conducted wi<strong>th</strong> low So/Xo (initial substrate<br />
concentration/biomass concentration) ratio. The oxygen uptake rate (OUR) was measured<br />
until <strong>th</strong>e OUR re<strong>ac</strong>hes a constant value, which is approximately equal to OUR in <strong>th</strong>e<br />
endogenous phase (Ekama, et al., 1986). The results from <strong>th</strong>e respirometric experiments<br />
would provide <strong>th</strong>e OUR data which can be applied to evaluate <strong>th</strong>e inhibition effects <strong>of</strong><br />
ammonia on <strong>th</strong>e microorganisms. Ammonium chloride (NH4Cl) was used as a source <strong>of</strong><br />
ammonia. The NH4-N concentration was varied from 200 to 2,000 mg/L.<br />
Table 3.3 Operating Conditions for Yeast and B<strong>ac</strong>teria Mixtures in Respirometer<br />
4<br />
3<br />
1 5<br />
6<br />
1. Respiration Cell 2. Water J<strong>ac</strong>ket 3. Air Diffuser<br />
4. DO Probe 5. Magnetic Bar 6. Magnetic Stirrer<br />
7. Expansion Funnel 8. DO Meter 9. Recorder<br />
Operating Conditions Yeast Mixture B<strong>ac</strong>teria Mixture<br />
pH 3.5 to 3.8 6.8 to 7.0<br />
Temperature ( o C) 30±0.5 30±0.5<br />
MLVSS (mg/L) 800 to 1,000 800 to 1,000<br />
So/Xo ratio 0.01 to 0.02 0.01 to 0.02<br />
Suppressing nitrification None Adding 70 mg/L as NH3-N *<br />
Remark: * Liebeskind (1999)<br />
The experimental procedure for <strong>th</strong>e determination <strong>of</strong> <strong>th</strong>e inhibitory effects is as<br />
follows:<br />
57<br />
9<br />
8
1. Obtaining endogenous sludge: 0.9 liter <strong>of</strong> fresh sludge wi<strong>th</strong>out <strong>th</strong>e substrate was<br />
obtained in a respirometer and aerated for two hours.<br />
2. Suppressing nitrification: Wi<strong>th</strong> high ammonia concentration during <strong>th</strong>e organic<br />
oxidation, <strong>th</strong>e oxygen uptake rate <strong>of</strong> nitrification process was constant. Hence,<br />
NH4Cl <strong>of</strong> concentration 70 mg/L was added.<br />
3. Recording endogenous oxygen uptake rate (OUR): After suppressing <strong>th</strong>e nitrification<br />
process, <strong>th</strong>e mixture was aerated for half an hour before measuring <strong>th</strong>e endogenous<br />
OUR.<br />
4. Adding substrate: An <strong>ac</strong>curate dose <strong>of</strong> substrate was injected into <strong>th</strong>e respirometer<br />
and <strong>th</strong>e total OUR was recorded by respirogram. Re-aeration was done once <strong>th</strong>e DO<br />
concentration dropped below 2 mg/L.<br />
3.4.2 Lead Toxicity<br />
The lead toxicity on <strong>th</strong>e b<strong>ac</strong>terial and yeast culture was conducted in <strong>th</strong>e same<br />
manner as described in <strong>th</strong>e section 3.4.1. Lead nitrate (Pb (NO3)2) was used as Lead (Pb)<br />
source. Soluble Pb concentration was varied from 0 to 20 mg/L. At e<strong>ac</strong>h concentration, <strong>th</strong>e<br />
sample was filtered wi<strong>th</strong> 0.45 µm membrane filter and soluble Pb concentration was<br />
analyzed using an atomic absorption spectrophotometer (AAS).<br />
3.5 Ammonia Stripping<br />
The char<strong>ac</strong>teristics <strong>of</strong> le<strong>ac</strong>hate used for <strong>th</strong>e experiment are as described in Table 3.1.<br />
The summary <strong>of</strong> <strong>th</strong>e experiments conducted in order to optimize ammonia stripping is<br />
illustrated in Figure 3.4.<br />
The efficiency <strong>of</strong> ammonia stripping in ammonia removal was tested varying <strong>th</strong>ree<br />
parameters namely- pH, cont<strong>ac</strong>t time and <strong>th</strong>e velocity gradient.<br />
The experiments conducted are as follows:<br />
1. Optimum pH for air stripping: The pH was varied from 9-12 (9, 10, 11, and 12) using<br />
12 N NaOH solution. The removal efficiency <strong>of</strong> ammonia at varying pH was<br />
assessed wi<strong>th</strong> a velocity gradient <strong>of</strong> 2,850 s -1 for two hours.<br />
2. Optimum velocity gradient and cont<strong>ac</strong>t time: After <strong>th</strong>e optimum pH was obtained,<br />
<strong>th</strong>e velocity gradient and <strong>th</strong>e cont<strong>ac</strong>t time were varied. The velocity gradients at<br />
which <strong>th</strong>e experiment was done were 1,530, 2,850, and 4,330 s -1 . The cont<strong>ac</strong>t time<br />
was varied from 1 to 6 hours.<br />
58
Figure 3.4 Experiments Conducted to Optimize Ammonia Stripping<br />
3.6 Membrane Biore<strong>ac</strong>tor<br />
3.6.1 Membrane Resistance Measurement<br />
The new membrane module requires a test in order to find out <strong>th</strong>e initial membrane<br />
resistance. Membrane resistance was measured based on <strong>th</strong>e resistance-in-series model<br />
which provides a simple means <strong>of</strong> describing <strong>th</strong>e relationship between permeate flux and<br />
trans-membrane pressure. According to <strong>th</strong>is model, it is expressed by <strong>th</strong>e following<br />
equation:<br />
Where:<br />
NaOH Solution<br />
J = TMP Eq. 3.1<br />
µ Rt<br />
J = permeate flux (m 3 /m 2 .s)<br />
TMP = trans-membrane pressure (Pa)<br />
µ = permeate viscosity (Pa.s)<br />
Rt = total resistance for filtration (1/m)<br />
For fur<strong>th</strong>er understanding <strong>of</strong> <strong>th</strong>e components <strong>of</strong> membrane resistances causing <strong>th</strong>e<br />
membrane clogging, <strong>th</strong>e total resistance (Rt) was measured right after <strong>th</strong>e run wi<strong>th</strong> <strong>th</strong>e<br />
membrane still in its clogging condition. Rm and Rn were obtained by measuring <strong>th</strong>e<br />
resistance <strong>of</strong> <strong>th</strong>e membrane after being washed wi<strong>th</strong> tap water to remove <strong>th</strong>e cake layer.<br />
The membrane resistance at <strong>th</strong>e beginning <strong>of</strong> <strong>th</strong>e run after chemical clean was considered<br />
as Rm. Rc Value was derived from Rt, Rm, and Rn using Equation 3.2.<br />
59<br />
Le<strong>ac</strong>hate<br />
pH Adjustment<br />
(for pH 9, 10, 11 and 12)<br />
Variation <strong>of</strong> Velocity Gradient<br />
and Cont<strong>ac</strong>t Time<br />
(for 2, 3, 4, 5 and 6 h)<br />
Control<br />
1,530 s -1<br />
2,850 s -1<br />
4,330 s -1
Where:<br />
Rt = Rm + Rn + Rc Eq. 3.2<br />
Rm = intrinsic resistance (1/m)<br />
Rn = resistance due to irreversible fouling (1/m)<br />
Rc = resistance due to cake layer (1/m)<br />
The membrane after clogging was taken out <strong>of</strong> <strong>th</strong>e re<strong>ac</strong>tor for cleaning. The<br />
membrane was first cleaned wi<strong>th</strong> tap water to remove <strong>th</strong>e cake layer att<strong>ac</strong>hing on <strong>th</strong>e<br />
membrane surf<strong>ac</strong>e follows by chemical cleaning as listed in Table 3.4 until <strong>th</strong>e membrane<br />
resistance was recovered to <strong>th</strong>e initial membrane resistance.<br />
Table 3.4 Description <strong>of</strong> <strong>th</strong>e Chemical Cleaning<br />
Stage Cleaning Agent Concentration Running Time (min)<br />
1 NaOH 3% by weight 20<br />
2 Ultra pure water 10<br />
3 HNO3 1% by weight 20<br />
4 Ultra pure water 10<br />
3.6.2 Experimental Set-up<br />
The experiments were conducted in two re<strong>ac</strong>tors namely: (1) yeast membrane<br />
biore<strong>ac</strong>tor (YMBR), and (2) b<strong>ac</strong>terial membrane biore<strong>ac</strong>tor (BMBR) as shown in Figure<br />
3.5. The re<strong>ac</strong>tor and <strong>th</strong>e membrane dimensions <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast biore<strong>ac</strong>tor were<br />
similar. The experimental set-up consists <strong>of</strong> a feed tank pl<strong>ac</strong>ed above <strong>th</strong>e biore<strong>ac</strong>tors. The<br />
volume <strong>of</strong> <strong>th</strong>e feed entering <strong>th</strong>e biore<strong>ac</strong>tor from <strong>th</strong>e feed tank was maintained by a level<br />
controller tank. A volume <strong>of</strong> 5L was maintained in <strong>th</strong>e biore<strong>ac</strong>tor. The technical details <strong>of</strong><br />
<strong>th</strong>e membrane biore<strong>ac</strong>tor are given in Table 3.5.<br />
Table 3.5 Technical Parameters <strong>of</strong> <strong>th</strong>e Experimental Plant<br />
Parameters Description<br />
Manuf<strong>ac</strong>ture Mitsubishi Rayon<br />
Model STNM424<br />
Membrane surf<strong>ac</strong>e (m 2 ) 0.42<br />
Type <strong>of</strong> module Hollow fibre<br />
Membrane material Polye<strong>th</strong>ylene<br />
Nominal pore size (µm) 0.1<br />
Re<strong>ac</strong>tor shape Cylindrical<br />
Re<strong>ac</strong>tor material Transparent <strong>ac</strong>rylic<br />
Re<strong>ac</strong>tor diameter (cm) 10<br />
Re<strong>ac</strong>tor volume (L) 5<br />
Aeration Stone diffuser<br />
B<strong>ac</strong>kwashing Air b<strong>ac</strong>kwash<br />
Cleaning 3% NaOH and 1% HNO3<br />
60
Le<strong>ac</strong>hate<br />
Option<br />
Ammonia Stripping<br />
Re<strong>ac</strong>tor<br />
Feed Tank<br />
P<br />
Level Control<br />
Tank<br />
Air Compressor<br />
Air Compressor<br />
Air Filter<br />
Pressure<br />
Gauge<br />
Air Outlet<br />
Figure 3.5 Schematic Diagrams <strong>of</strong> Membrane Biore<strong>ac</strong>tor wi<strong>th</strong> and wi<strong>th</strong>out Ammonia Stripping<br />
61<br />
Timer<br />
Yeast Membrane Biore<strong>ac</strong>tor<br />
pH Controller<br />
Dosing<br />
Pump<br />
P<br />
V<strong>ac</strong>uum<br />
Gauge<br />
Suction Pump<br />
P<br />
Air Diffuser<br />
Excess<br />
Sludge<br />
Treated Water<br />
Tank<br />
Sulfuric Acid<br />
Solution<br />
Level Control<br />
Tank<br />
Air Compressor<br />
Air Compressor<br />
Air Filter<br />
Pressure<br />
Gauge<br />
Air Outlet<br />
Timer<br />
pH Controller<br />
Dosing<br />
Pump<br />
P<br />
B<strong>ac</strong>teria Membrane Biore<strong>ac</strong>tor<br />
V<strong>ac</strong>uum<br />
Gauge<br />
Suction Pump<br />
P<br />
Air Diffuser<br />
Excess<br />
Sludge<br />
Treated Water<br />
Tank<br />
Sulfuric Acid<br />
Solution
The re<strong>ac</strong>tors were continuously aerated wi<strong>th</strong> <strong>th</strong>e help <strong>of</strong> stone diffusers pl<strong>ac</strong>ed at <strong>th</strong>e<br />
bottom <strong>of</strong> <strong>th</strong>e re<strong>ac</strong>tors. The polye<strong>th</strong>ylene hollow fibre membrane was kept in <strong>th</strong>e upper end<br />
<strong>of</strong> <strong>th</strong>e re<strong>ac</strong>tors. Peristaltic pumps were used to wi<strong>th</strong>draw permeate from <strong>th</strong>ese membrane<br />
modules. The re<strong>ac</strong>tors were also equipped wi<strong>th</strong> <strong>th</strong>e pH meter to monitor pH continuously.<br />
The pH <strong>of</strong> <strong>th</strong>e yeast and b<strong>ac</strong>terial re<strong>ac</strong>tor was maintained wi<strong>th</strong>in <strong>th</strong>e range <strong>of</strong> 3.5 to 3.8 and<br />
6.8 to 7, respectively wi<strong>th</strong> <strong>th</strong>e help <strong>of</strong> an external dosing pump. The DO in <strong>th</strong>e re<strong>ac</strong>tors was<br />
maintained around 2-4 mg/L.<br />
Bo<strong>th</strong> <strong>th</strong>e biore<strong>ac</strong>tors were operated wi<strong>th</strong> periodic air b<strong>ac</strong>kwashing. The filtration<br />
cycle <strong>of</strong> <strong>th</strong>e re<strong>ac</strong>tor consists <strong>of</strong> 25 minutes <strong>of</strong> filtration, 3 minutes <strong>of</strong> air b<strong>ac</strong>kwashing at a<br />
pressure <strong>of</strong> 300 kPa, and 1 minute <strong>of</strong> air release. The operation <strong>of</strong> filtration, b<strong>ac</strong>kwash and<br />
release air was alternatively controlled wi<strong>th</strong> an intermittent controller and solenoid valves.<br />
The trans-membrane pressure (TMP) was measured using a mercury manometer.<br />
Sampling from <strong>th</strong>e re<strong>ac</strong>tors was done from <strong>th</strong>e sampling port. The sludge from <strong>th</strong>e<br />
re<strong>ac</strong>tor could be wi<strong>th</strong>drawn from a sampling port present in <strong>th</strong>e bottom <strong>of</strong> <strong>th</strong>e re<strong>ac</strong>tor. The<br />
treated le<strong>ac</strong>hate was collected in a container kept at <strong>th</strong>e side <strong>of</strong> <strong>th</strong>e re<strong>ac</strong>tor. The treated<br />
effluent corresponds to permeate from <strong>th</strong>e membrane biore<strong>ac</strong>tor.<br />
3.6.3 Parametric Studies<br />
The experiments were done by varying <strong>th</strong>e volumetric loading. The different<br />
organic loading rates (OLR) used in <strong>th</strong>is experiment are summarized in Table 3.6. E<strong>ac</strong>h<br />
volumetric loading was maintained at least for 25 days. Fur<strong>th</strong>ermore, <strong>th</strong>e excess sludge<br />
was periodically wi<strong>th</strong>drawn to maintain a mean biomass concentration <strong>of</strong> 10,000 to 12,000<br />
mg/L <strong>of</strong> MLSS. The pH in <strong>th</strong>e YMBR system and BMBR system was maintained around<br />
3.5 to 3.8 and 6.8 to 7.0, respectively. The varied mean hydraulic retention time in which<br />
<strong>th</strong>e experiment was conducted are 12, 16, 20 and 24 hours. The hydraulic loading varied<br />
from 6.75 to 17.88 kg COD/m 3 .d .<br />
Table 3.6 Experimental Operating Conditions <strong>of</strong> YMBR and BMBR Systems<br />
Stage Time<br />
(days)<br />
1<br />
1-25<br />
2<br />
26-60<br />
3<br />
61-149<br />
4<br />
150-181<br />
3.6.4 Molecular Weight Distribution<br />
Mean HRT<br />
(h)<br />
24<br />
20<br />
16<br />
12<br />
62<br />
OLR<br />
(kg COD/m 3 .d)<br />
6.75-8.33<br />
7.60-11.14<br />
9.54-14.40<br />
13.92-17.88<br />
To investigate <strong>th</strong>e composition <strong>of</strong> organic content in <strong>th</strong>e le<strong>ac</strong>hate on <strong>th</strong>e basis <strong>of</strong> <strong>th</strong>eir<br />
molecular weight, ultrafiltration membrane (UF) was used. Ultrafiltration was performed<br />
in a 300 ml cell, using flat circular membrane <strong>of</strong> 76 cm diameter wi<strong>th</strong> molecular weight<br />
cut-<strong>of</strong>f (MWCO) <strong>of</strong> 5,000, 10,000, and 50,000 Daltons (Da). Nitrogen gas was used to<br />
apply pressure in <strong>th</strong>e UF cell at about 2 bars (Gourdon, et al., 1989; Huang, at el., 2000).<br />
The <strong>th</strong>ree types <strong>of</strong> UF wi<strong>th</strong> molecular weight cut<strong>of</strong>f ranges are presented in Table 3.7. The<br />
fr<strong>ac</strong>tionated organics in <strong>th</strong>e treated le<strong>ac</strong>hate were also measured to find out <strong>th</strong>e organic<br />
removal efficiency <strong>of</strong> <strong>th</strong>e membrane biore<strong>ac</strong>tor in terms <strong>of</strong> <strong>th</strong>eir molecular weight. The<br />
organics were fr<strong>ac</strong>tionated into four groups based on <strong>th</strong>eir molecular weight (MW): (1)
MW larger <strong>th</strong>an 50 kDa, (2) MW between 10 kDa and 50 kDa, (3) MW between 5 kDa and<br />
10 kDa, and (4) MW less <strong>th</strong>an 5 kDa. The procedure for molecular weight distribution<br />
study is described in Figure 3.6.The procedure for molecular weight distribution is as<br />
follows:<br />
1. 100 mL <strong>of</strong> sample was filtered in a 0.45 µm membrane before fr<strong>ac</strong>tionating it wi<strong>th</strong><br />
UF at 50 kDa MWCO at a pressure <strong>of</strong> 2 bars for 30 minutes.<br />
2. The permeate <strong>of</strong> <strong>th</strong>e UF membrane used for 50 kDa MW was collected and fur<strong>th</strong>er<br />
fr<strong>ac</strong>tionated wi<strong>th</strong> serial processing me<strong>th</strong>od using <strong>th</strong>e corresponding UF at 10 kDa,<br />
and 5 kDa MW, using <strong>th</strong>e same mode <strong>of</strong> operation.<br />
3. The volume <strong>of</strong> retentate <strong>of</strong> e<strong>ac</strong>h fr<strong>ac</strong>tion and permeate obtained after 5 kDa MW UF<br />
were measured and analyzed for COD concentration.<br />
Le<strong>ac</strong>hate<br />
50 kDa MW<br />
Permeate<br />
10 kDa MW<br />
Permeate<br />
5 kDa MW<br />
Permeate<br />
Figure 3.6 Me<strong>th</strong>odology for Performing Molecular Weight Cut-<strong>of</strong>f Distribution<br />
63<br />
Retentate<br />
Retentate<br />
Retentate
Table 3.7 Char<strong>ac</strong>teristics <strong>of</strong> Ultrafiltration Membrane<br />
UF Membrane Types MWCO (kDa)<br />
Koch membrane, M-100 50<br />
Koch membrane, K-131 10<br />
Koch membrane, K-328 5<br />
3.6.5 Sludge Char<strong>ac</strong>terization<br />
The variation in sludge char<strong>ac</strong>teristics was estimated in bo<strong>th</strong> <strong>th</strong>e re<strong>ac</strong>tors. The<br />
YMBR and BMBR systems can be divided into <strong>th</strong>ree zones based on <strong>th</strong>e membrane cycle.<br />
Based on <strong>th</strong>e membrane fouling, <strong>th</strong>e sludge was sampled for analysis. Sludge properties<br />
which were determined in bo<strong>th</strong> <strong>th</strong>e re<strong>ac</strong>tors were <strong>th</strong>e extra cellular polymer substances<br />
(EPS), sludge volume index (SVI), capillary suction time (CST), MLSS and viscosity.<br />
3.7 Ammonia Stripping Coupled Membrane Biore<strong>ac</strong>tor<br />
The membrane biore<strong>ac</strong>tor was coupled wi<strong>th</strong> ammonia stripping to find out <strong>th</strong>e<br />
treatment efficiency <strong>of</strong> <strong>th</strong>is combined treatment system. The experimental set-up consists<br />
<strong>of</strong> two treatment systems, namely: ammonia stripping and membrane biore<strong>ac</strong>tor (MBR) as<br />
shown in Figure 3.5. Figure 3.7 show <strong>th</strong>e procedure <strong>of</strong> <strong>th</strong>e coupling ammonia stripping<br />
wi<strong>th</strong> MBR.<br />
The operating conditions for ammonia stripping process were based on <strong>th</strong>e results<br />
obtained from <strong>th</strong>e previous experiment. Mean velocity gradient, pH and <strong>th</strong>e mixing time<br />
were based on <strong>th</strong>e experimental results obtained after optimization <strong>of</strong> <strong>th</strong>e ammonia<br />
stripping conditions. The ammonia stripped le<strong>ac</strong>hate was used as a feed in bo<strong>th</strong> <strong>th</strong>e YMBR<br />
and BMBR re<strong>ac</strong>tors. The design <strong>of</strong> <strong>th</strong>e re<strong>ac</strong>tors used for <strong>th</strong>e experiment was similar to<br />
biore<strong>ac</strong>tor as described 3.6.2.<br />
The HRT used in <strong>th</strong>is experiment are from <strong>th</strong>e results obtained after performing <strong>th</strong>e<br />
parametric studies as described in session 3.6.3. The excess sludge was periodically<br />
wi<strong>th</strong>drawn to maintain a mean biomass <strong>of</strong> 10,000 to 12,000 mg/L <strong>of</strong> MLSS. The biore<strong>ac</strong>tor<br />
was assessed in terms <strong>of</strong> <strong>th</strong>e membrane performance in le<strong>ac</strong>hate treatment and sludge<br />
char<strong>ac</strong>teristics.<br />
64
Figure 3.7 Flowchart Showing Ammonia Stripping Coupled MBR Process<br />
3.8 Analytical Me<strong>th</strong>ods<br />
Raw Le<strong>ac</strong>hate<br />
Ammonia Stripping<br />
Membrane Biore<strong>ac</strong>tor using B<strong>ac</strong>terial and<br />
Yeast Cultures<br />
The analyses performed were in <strong>ac</strong>cordance wi<strong>th</strong> <strong>th</strong>e Standard Me<strong>th</strong>ods (APHA, et<br />
al., 1998). Table 3.8 lists parameters and <strong>th</strong>eir analysis me<strong>th</strong>ods in <strong>th</strong>is study.<br />
Extr<strong>ac</strong>tion <strong>of</strong> Extr<strong>ac</strong>ellular Polymeric Substances (EPS)<br />
The quantification <strong>of</strong> EPS in biomass was analyzed using <strong>th</strong>ermal extr<strong>ac</strong>tion me<strong>th</strong>od<br />
(Chang and Lee, 1998). A measured volume <strong>of</strong> sludge solid was centrifuged in order to<br />
subtr<strong>ac</strong>t <strong>th</strong>e soluble EPS at 3,200 rpm for 30 min from bound EPS. After collecting <strong>th</strong>e<br />
soluble EPS, <strong>th</strong>e remaining pellet was resuspended wi<strong>th</strong> 0.9% NaCl solution before heating<br />
at 80 o C for 1 h. The extr<strong>ac</strong>ted solution was separated from <strong>th</strong>e sludge solids by<br />
centrifugation at 3,200 rpm for 30 min. The obtained supernatant was <strong>th</strong>e bound EPS. The<br />
quantity <strong>of</strong> extr<strong>ac</strong>ted EPS was measured by measuring total organic carbon (TOC),<br />
proteins and carbohydrates.<br />
65<br />
Operating Conditions:<br />
- pH<br />
- Velocity Gradient<br />
- Operation Time
Table 3.8 Parameters and Their Analytical Me<strong>th</strong>ods<br />
Parameter<br />
Me<strong>th</strong>od <strong>of</strong> Analysis<br />
66<br />
Equipment Used<br />
pH pH meter pH meter<br />
DO DO meter DO meter<br />
COD Dichromate reflux Titration<br />
BOD Oxitop Oxitop bottles<br />
TOC Combustion me<strong>th</strong>od TOC analyser<br />
Pb<br />
Flame atomic absorption<br />
spectrometry<br />
Atomic absorption spectrometry<br />
Ammonia Distillation Titration<br />
Nitrite and Nitrate Colorimetric UV-visible spectrophotometer<br />
TKN M<strong>ac</strong>ro-Kjeldahl Titration<br />
Phosphate Ascobic <strong>ac</strong>id UV-visible spectrophotometer<br />
MLSS Dried at 103-105 o C Filter/Oven<br />
MLVSS Ignited at 550 o C Furn<strong>ac</strong>e<br />
TDS Conductivity meter Conductivity meter<br />
Conductivity Conductivity meter Conductivity meter<br />
MWCO Membrane filtration UF membrane module<br />
SVI<br />
Settle sludge volume<br />
after 30 minutes<br />
1000 ml cylinder<br />
Viscosity<br />
Rotating torque cylinder at 100<br />
rpm<br />
Viscometer<br />
CST Capillary time CST apparatus<br />
EPS<br />
Thermal and<br />
centrifugation me<strong>th</strong>od<br />
Centrifugal equipment<br />
Proteins Lowry Spectrophotometer<br />
Carbohydrates Phenolic-sulfuric <strong>ac</strong>id Spectrophotometer
Chapter 4<br />
Results and Discussion<br />
4.1 Simulation <strong>of</strong> Le<strong>ac</strong>hate Char<strong>ac</strong>teristic for Treatment <strong>of</strong> Middle Aged Le<strong>ac</strong>hate<br />
Le<strong>ac</strong>hate varies widely in quantity and in composition from one pl<strong>ac</strong>e to ano<strong>th</strong>er<br />
(Kennedy, et al., 1988). Such variability along wi<strong>th</strong> o<strong>th</strong>er f<strong>ac</strong>tors make <strong>th</strong>e applicability <strong>of</strong><br />
a me<strong>th</strong>od to treat le<strong>ac</strong>hate highly dependent on <strong>th</strong>e char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate and<br />
tolerance <strong>of</strong> <strong>th</strong>e me<strong>th</strong>od against changes in le<strong>ac</strong>hate quality (Henry, et al., 1982). As<br />
mentioned in section 2.13.1, it is difficult to predict <strong>th</strong>e applicability <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate<br />
treatment sequence wi<strong>th</strong> varying le<strong>ac</strong>hate quality. To overcome <strong>th</strong>is problem, le<strong>ac</strong>hate wi<strong>th</strong><br />
a quality emulating <strong>th</strong>e medium landfill le<strong>ac</strong>hate was simulated, and used in <strong>th</strong>is<br />
experimental work.<br />
To arrive at <strong>th</strong>e appropriate le<strong>ac</strong>hate quality to be taken for <strong>th</strong>e study, a survey on <strong>th</strong>e<br />
medium aged le<strong>ac</strong>hate in <strong>Asian</strong> context is required. Table 2.3 gives <strong>th</strong>e typical<br />
char<strong>ac</strong>teristics <strong>of</strong> <strong>th</strong>e middle aged landfill le<strong>ac</strong>hate. The medium-aged le<strong>ac</strong>hate contains<br />
COD ranging <strong>of</strong> 5,000 to 10,000 mg/L and BOD/COD ratio <strong>of</strong> 0.1 to 0.5 (Qasim and<br />
Chiang, 1994; Amokrane, et al., 1997). The medium landfill le<strong>ac</strong>hate is usually less<br />
biodegradable <strong>th</strong>an <strong>th</strong>e young le<strong>ac</strong>hate. The high ammonium concentration <strong>of</strong> around 2,000<br />
mg/L makes <strong>th</strong>e medium aged le<strong>ac</strong>hate treatment even more complicated. The NH4 + -N is<br />
dominant among <strong>th</strong>e nitrogen forms making it an important parameter to be considered in<br />
le<strong>ac</strong>hate treatment. Ano<strong>th</strong>er important parameter taken into consideration is <strong>th</strong>e alkalinity.<br />
The alkalinity is also found to be high in le<strong>ac</strong>hate and significant in le<strong>ac</strong>hate treatment. As<br />
<strong>th</strong>e le<strong>ac</strong>hate is nutrient deficient in terms <strong>of</strong> phosphorus, and <strong>of</strong>ten phosphorous<br />
supplement was added to enhance <strong>th</strong>e le<strong>ac</strong>hate treatment. Based on <strong>th</strong>e literature review, a<br />
simulated le<strong>ac</strong>hate quality was used wi<strong>th</strong> BOD/COD ratio ranging from 0.35 to 0.45, COD<br />
ranging from 7,000 to 9,000 mg/L, and total nitrogen ranging from 1,800 to 2,000 mg/L as<br />
described in Table 3.1.<br />
The le<strong>ac</strong>hate simulated for <strong>th</strong>e study was prepared by combining <strong>th</strong>e le<strong>ac</strong>hate<br />
collected from Pa<strong>th</strong>um<strong>th</strong>ani Landfill Site (PS) and Ram-Indra Transfer Station (RIS).<br />
Table B-1 <strong>of</strong> Appendix B gives <strong>th</strong>e le<strong>ac</strong>hate quality <strong>of</strong> <strong>th</strong>e two sites along wi<strong>th</strong> <strong>th</strong>e mixed<br />
le<strong>ac</strong>hate quality. The BOD/COD <strong>of</strong> <strong>th</strong>e mixed le<strong>ac</strong>hate was found to be around 0.44-0.45.<br />
Table 4.1 presents <strong>th</strong>e consistency <strong>of</strong> <strong>th</strong>e simulated le<strong>ac</strong>hate used in <strong>th</strong>e study.<br />
Table 4.1 Compositions <strong>of</strong> Le<strong>ac</strong>hate Simulated from Le<strong>ac</strong>hates Obtained from Pa<strong>th</strong>um<strong>th</strong>ani<br />
Landfill Site (PS) and Ram-Indra Transfer Station (RIS)<br />
COD BOD BOD/COD NH3-N TKN<br />
(mg/L) (mg/L)<br />
(mg/L) (mg/L)<br />
7,715 3,484 0.45 1,791 2,072<br />
7,733 3,460 0.45 1,623 1,850<br />
7,404 3,353 0.45 1,624 1,969<br />
7,248 3,205 0.44 1,558 1,898<br />
67
4.2 Biokinetic Studies<br />
Bio-kinetic experiments are important in any biological treatment systems. A<br />
biological system consists <strong>of</strong> a mixture <strong>of</strong> organisms wi<strong>th</strong> different grow<strong>th</strong> patterns and<br />
degradation rates. The overall grow<strong>th</strong> and degradation rate is important for <strong>th</strong>e degradation<br />
<strong>of</strong> <strong>th</strong>e pollutants present in <strong>th</strong>e waste. Therefore, bio-kinetic studies were conducted to get<br />
an overall picture <strong>of</strong> <strong>th</strong>e degradation potential and grow<strong>th</strong> <strong>of</strong> <strong>th</strong>e microorganisms used in<br />
<strong>th</strong>e degradation pattern.<br />
4.2.1 Acclimatization <strong>of</strong> Mixed Yeast and B<strong>ac</strong>terial Sludge<br />
Prior to <strong>th</strong>e biokinetic study, it is necessary to <strong>ac</strong>climatize <strong>th</strong>e organisms to <strong>th</strong>e<br />
prevailing toxic conditions <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate having high COD and ammonia concentrations<br />
along wi<strong>th</strong> o<strong>th</strong>er humic organic components. After <strong>ac</strong>climatization <strong>of</strong> <strong>th</strong>e culture to be used,<br />
a rich mixture <strong>of</strong> resistant le<strong>ac</strong>hate degrading organisms could be obtained. In <strong>th</strong>e present<br />
experiment, b<strong>ac</strong>terial and yeast culture were used to degrade <strong>th</strong>e le<strong>ac</strong>hate in <strong>th</strong>e membrane<br />
biore<strong>ac</strong>tors. Preceding <strong>ac</strong>climatization <strong>of</strong> <strong>th</strong>e yeast culture, to obtain a wide range <strong>of</strong> <strong>th</strong>e<br />
yeast species, yeast was enriched using <strong>th</strong>e standard enrichment technique. The enrichment<br />
was completely <strong>ac</strong>complished once <strong>th</strong>e yeast re<strong>ac</strong>hed a MLSS concentration <strong>of</strong> 3,000 mg/L.<br />
The <strong>ac</strong>climatization and <strong>th</strong>e enrichment <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast culture was done as<br />
described in section 3.3.2. The pH <strong>of</strong> <strong>th</strong>e yeast culture was maintained at around 3.5 as<br />
yeast <strong>ac</strong>tivity is pronounced at low pH and <strong>th</strong>is would also help in preventing b<strong>ac</strong>terial<br />
contamination.<br />
(1) Organic Removal<br />
The <strong>ac</strong>climatization <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast culture were done as described in<br />
section 3.3.2 wi<strong>th</strong> <strong>th</strong>e simulated medium-aged landfill le<strong>ac</strong>hate having char<strong>ac</strong>teristic given<br />
in section 3.2 wi<strong>th</strong> variation in COD load, which was step-wise increased to finally obtain<br />
an <strong>ac</strong>climatized culture. The operation conditions for <strong>th</strong>e <strong>ac</strong>climatization process are<br />
mentioned in <strong>th</strong>e Table 3.2. The organic load while <strong>ac</strong>climatizing was step wise increased<br />
from 3,800 to 7,300 for b<strong>ac</strong>terial as well as yeast culture. The <strong>ac</strong>climatization was done<br />
step-wise until a COD removal approximately 70% could be <strong>ac</strong>hieved. The changes in <strong>th</strong>e<br />
biomass concentration along wi<strong>th</strong> <strong>th</strong>e F/M ratio and COD removal efficiencies were<br />
noticed. These measured parameters are given in Table B-2 and B-3 <strong>of</strong> Appendix B.<br />
Acclimatization <strong>of</strong> yeast and b<strong>ac</strong>terial culture took about 67 days. The change in <strong>th</strong>e<br />
COD removal efficiency and <strong>th</strong>e F/M ratio is given in Figure 4.1 and 4.2. It was found <strong>th</strong>at<br />
after 67 days, <strong>th</strong>e COD removal efficiency wi<strong>th</strong> yeast culture was higher <strong>th</strong>an <strong>th</strong>at <strong>of</strong><br />
b<strong>ac</strong>terial culture. The COD removal efficiency re<strong>ac</strong>hed 75% in yeast sludge compared to<br />
66% in <strong>th</strong>e b<strong>ac</strong>terial sludge. This indicates <strong>th</strong>at, yeast culture could probably be more<br />
effective in le<strong>ac</strong>hate treatment <strong>th</strong>an <strong>th</strong>e b<strong>ac</strong>terial culture. However, as <strong>th</strong>e results obtained<br />
are not sufficient to conclude <strong>th</strong>at yeast system has a better performance <strong>th</strong>an b<strong>ac</strong>teria<br />
system, fur<strong>th</strong>er investigation is necessary. F/M ratio decreased from 1.01 to 0.62 kg<br />
COD/kg SS.d in <strong>th</strong>e yeast culture and from 1.45 to 1.14 kg COD/kg SS.d in <strong>th</strong>e b<strong>ac</strong>terial<br />
sludge. The difference between <strong>th</strong>e F/M ratios in <strong>th</strong>e b<strong>ac</strong>terial culture was not as much as<br />
<strong>th</strong>e yeast culture. This suggests <strong>th</strong>at <strong>th</strong>e grow<strong>th</strong> <strong>of</strong> <strong>th</strong>e yeast culture was more prominent<br />
<strong>th</strong>an <strong>th</strong>e b<strong>ac</strong>terial culture. Lower <strong>th</strong>e F/M ratio, <strong>th</strong>e better is <strong>th</strong>e le<strong>ac</strong>hate treatment cap<strong>ac</strong>ity<br />
<strong>of</strong> <strong>th</strong>e system. This could be <strong>th</strong>e reason for <strong>th</strong>e better removal efficiency <strong>of</strong> COD by <strong>th</strong>e<br />
yeast culture.<br />
68
COD Removal Effeciency (%)<br />
COD Removal Effeciency (%) .<br />
80<br />
70<br />
60<br />
50<br />
40<br />
80<br />
70<br />
60<br />
50<br />
40<br />
0 10 20 30 40 50 60 70 80<br />
Time (Days)<br />
Figure 4.1 Variation in F/M and COD Removal Efficiency in Yeast Sludge<br />
Figure 4.2 Variation in F/M and COD Removal Efficiency in B<strong>ac</strong>terial Sludge<br />
69<br />
COD Removal Effeciency<br />
F/M Ratio<br />
COD Removal Effeciency<br />
F/M Ratio<br />
0 10 20 30 40 50 60 70 80<br />
Time (Days)<br />
1.60<br />
1.40<br />
1.20<br />
1.00<br />
0.80<br />
0.60<br />
0.40<br />
1.60<br />
1.40<br />
1.20<br />
1.00<br />
0.80<br />
0.60<br />
0.40<br />
F/M (kgCOD/kg SS.d)<br />
F/M (kgCOD/kg SS.d)
(2) Biomass<br />
The grow<strong>th</strong> <strong>of</strong> biomass is important for <strong>th</strong>e treatment <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate. Sufficient<br />
MLSS should be obtained in order to get a good COD removal efficiency. The change in<br />
<strong>th</strong>e biomass for <strong>th</strong>e b<strong>ac</strong>terial and <strong>th</strong>e yeast culture when stepwise COD load was increased<br />
is illustrated in <strong>th</strong>e Figure 4.3 and 4.4. The initial MLSS <strong>of</strong> <strong>th</strong>e yeast re<strong>ac</strong>tor was around<br />
3,750 mg/L, while <strong>th</strong>e b<strong>ac</strong>terial initial sludge MLSS was 2,620 mg/L. The final MLSS <strong>of</strong><br />
yeast and b<strong>ac</strong>teria after <strong>ac</strong>climatization were 11,700 and 6,420 mg/L, respectively. The<br />
MLSS concentration maintained <strong>th</strong>roughout <strong>th</strong>e membrane biore<strong>ac</strong>tor experiment was<br />
about 10,000 mg/L for <strong>th</strong>e yeast re<strong>ac</strong>tor and 5, 000 mg/L for <strong>th</strong>e b<strong>ac</strong>terial re<strong>ac</strong>tor. The final<br />
MLSS in <strong>th</strong>e yeast system was about 3.12 times <strong>th</strong>e initial MLSS concentration which<br />
shows a 21 % increase in <strong>th</strong>e biomass. In <strong>th</strong>e b<strong>ac</strong>terial system, <strong>th</strong>e final MLSS was 2.5<br />
times initial biomass, which shows an increase <strong>of</strong> 14.5% in <strong>th</strong>e biomass. Once <strong>th</strong>e cultures<br />
have been <strong>ac</strong>climatized wi<strong>th</strong> a final le<strong>ac</strong>hate concentration having COD <strong>of</strong> 7,300 mg/L<br />
(approximately <strong>th</strong>e initial concentration to be used in <strong>th</strong>e biore<strong>ac</strong>tors), <strong>th</strong>e cultures was<br />
used for <strong>th</strong>e experimental studies.<br />
MLSS (mg/L)<br />
7000<br />
6000<br />
5000<br />
4000<br />
3000<br />
2000<br />
1000<br />
0<br />
0 10 20 30 40 50 60 70 80<br />
Time (Days)<br />
Figure 4.3 Increase in Biomass during Acclimatization <strong>of</strong> <strong>th</strong>e B<strong>ac</strong>terial Sludge<br />
70<br />
MLSS<br />
Influent COD<br />
9000<br />
8000<br />
7000<br />
6000<br />
5000<br />
4000<br />
3000<br />
Influent COD (mg/L) .
MLSS (mg/L)<br />
14000<br />
12000<br />
10000<br />
8000<br />
6000<br />
4000<br />
2000<br />
0<br />
0 10 20 30 40 50 60 70 80<br />
Time (Days)<br />
Figure 4.4 Increase in Biomass during Acclimatization <strong>of</strong> <strong>th</strong>e Yeast Sludge<br />
After <strong>th</strong>e <strong>ac</strong>climatization process, <strong>th</strong>e organisms were microscopically observed.<br />
The Figure 4.5 and 4.6 show <strong>th</strong>e yeast and <strong>th</strong>e b<strong>ac</strong>terial culture under <strong>th</strong>e microscope. The<br />
yeast cells contained egg-shaped and spherical cells. The b<strong>ac</strong>terial culture was dominated<br />
by <strong>th</strong>e rod-shaped organisms containing bo<strong>th</strong> gram positive and gram negative organisms.<br />
Figure 4.5 Predominantly Spherical and Egg-shaped Yeasts wi<strong>th</strong> Budding in <strong>th</strong>e Yeast<br />
Re<strong>ac</strong>tor (x1500)<br />
71<br />
MLSS<br />
Influent COD<br />
8500<br />
7500<br />
6500<br />
5500<br />
4500<br />
3500<br />
Influent COD (mg/L)
(a) (b)<br />
Figure 4.6 B<strong>ac</strong>teria Cells in <strong>th</strong>e Mixed B<strong>ac</strong>teria Sludge: a) Gram Negative and b) Gram<br />
Positive (x1500)<br />
4.2.2 Kinetics <strong>of</strong> Yeast and B<strong>ac</strong>terial Grow<strong>th</strong><br />
Optimum environmental conditions are important for <strong>th</strong>e grow<strong>th</strong> <strong>of</strong> <strong>th</strong>e<br />
microorganisms as well as <strong>th</strong>e degradation <strong>of</strong> <strong>th</strong>e organic components. To assess <strong>th</strong>e<br />
optimum conditions in <strong>th</strong>e systems, it is necessary to monitor <strong>th</strong>e grow<strong>th</strong> <strong>of</strong> <strong>th</strong>e<br />
microorganisms. This could be <strong>ac</strong>hieved in several ways. Respiration (oxygen<br />
consumption) is probably <strong>th</strong>e most widely tested and <strong>ac</strong>cepted b<strong>ac</strong>terial monitoring<br />
technique (Cairns and Van Der Schalie, 1980). Normally, b<strong>ac</strong>terial respiration results in a<br />
certain decrease in oxygen concentration in <strong>th</strong>e medium depending upon <strong>th</strong>e retention time<br />
<strong>of</strong> <strong>th</strong>e chamber and temperature. This oxygen uptake by <strong>th</strong>e organism can help us describe<br />
<strong>th</strong>e grow<strong>th</strong> pattern <strong>of</strong> <strong>th</strong>e microorganism. Reeves (1976) used <strong>th</strong>e respirometer to record<br />
<strong>th</strong>e oxygen uptake in <strong>th</strong>e <strong>ac</strong>tivated sludge unit.<br />
The Oxygen Uptake Rate (OUR) refers to <strong>th</strong>e rate <strong>of</strong> oxygen consumption by<br />
aerobic b<strong>ac</strong>teria per unit time (Chen, et al., 1997). It is produced by <strong>th</strong>e slope <strong>of</strong> <strong>th</strong>e<br />
relationship between <strong>th</strong>e dissolved oxygen and <strong>th</strong>e exposure time. By measuring <strong>th</strong>e<br />
oxygen uptake rate, one can indirectly obtain <strong>th</strong>e specific grow<strong>th</strong> rate <strong>of</strong> <strong>th</strong>e<br />
microorganisms as rate <strong>of</strong> <strong>th</strong>e oxygen uptake is stoichiometrically related to <strong>th</strong>e organic<br />
utilization rate and <strong>th</strong>e grow<strong>th</strong> rate. The operation condition used in <strong>th</strong>e biokinetic studies<br />
in <strong>th</strong>e b<strong>ac</strong>terial and yeast re<strong>ac</strong>tor is described in Table 3.3. In <strong>th</strong>e treatment process, <strong>th</strong>e<br />
substrate concentration and <strong>th</strong>e limiting nutrients has an effect on <strong>th</strong>e specific grow<strong>th</strong> rate<br />
<strong>of</strong> <strong>th</strong>e microorganism. The effect <strong>of</strong> <strong>th</strong>e substrate concentration in <strong>th</strong>e b<strong>ac</strong>terial and yeast<br />
culture is given <strong>th</strong>e Figure 4.7 and 4.8, respectively.<br />
72
Specific Grow<strong>th</strong> Rate<br />
( d -1 )<br />
0.50<br />
0.40<br />
0.30<br />
0.20<br />
0.10<br />
0.00<br />
0 10 20 30 40 50<br />
Substrate (mg COD/L)<br />
Figure 4.7 Specific Grow<strong>th</strong> Rate <strong>of</strong> Mixed B<strong>ac</strong>teria Sludge wi<strong>th</strong> Increasing Substrate<br />
Concentration<br />
Specific Grow<strong>th</strong> Rate<br />
(d -1 )<br />
0.30<br />
0.20<br />
0.10<br />
0.00<br />
0 10 20 30 40 50<br />
Substrate (mg COD/L)<br />
Figure 4.8 Specific Grow<strong>th</strong> Rate <strong>of</strong> Mixed Yeast Sludge wi<strong>th</strong> Increasing Substrate<br />
Concentration<br />
73
The various parameters concerned wi<strong>th</strong> biokinetic study <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast<br />
culture are given in Table C-1 and C-2 <strong>of</strong> Appendix C. The various biokinetic parameters<br />
were measured using <strong>th</strong>e Monad’s model. The substrate concentrations used in <strong>th</strong>e<br />
experiment from 5 to 40 mg/L and 7 to 42 mg/L wi<strong>th</strong> yeast and b<strong>ac</strong>terial culture,<br />
respectively. The rate <strong>of</strong> grow<strong>th</strong> <strong>of</strong> <strong>th</strong>e organisms in <strong>th</strong>e b<strong>ac</strong>terial culture was found to be<br />
0.009 to 0.03 mg COD/mg VSS. h and 0.008 to 0.02 mg COD/mg VSS. h in <strong>th</strong>e yeast<br />
culture when <strong>th</strong>e substrate concentration was gradually increased. The maximum yield<br />
coefficient was 0.60 mg VSS/mg COD in <strong>th</strong>e b<strong>ac</strong>terial culture and 0.51 mg VSS/mg COD<br />
in <strong>th</strong>e yeast culture. The important parameters for yeast and b<strong>ac</strong>teria sludge are presented<br />
in Table 4.2. Additionally, estimation <strong>of</strong> <strong>th</strong>e parameter group (µmax/(Y.Ks)) is used as a<br />
measure for comparing <strong>th</strong>e biodegradation kinetics, as suggested by Grady, et al. (1999).<br />
Comparison <strong>of</strong> <strong>th</strong>e biokinetic parameters for bo<strong>th</strong> yeast and b<strong>ac</strong>teria sludge treating<br />
le<strong>ac</strong>hate illustrates <strong>th</strong>at <strong>th</strong>e maximum specific grow<strong>th</strong> rate (µmax) and <strong>th</strong>e substrate<br />
utilization rate (k) were determined to be less <strong>th</strong>an <strong>th</strong>e typical values for domestic<br />
wastewater whereas Y value was in <strong>th</strong>e range <strong>of</strong> domestic wastewater. There is a case <strong>th</strong>at<br />
<strong>th</strong>e µmax and Y values are higher <strong>th</strong>an usual. This might be noted <strong>th</strong>at <strong>th</strong>e µmax and Y values<br />
are not always indicated <strong>th</strong>e biodegradability because <strong>th</strong>ere are o<strong>th</strong>er f<strong>ac</strong>tors <strong>th</strong>at control<br />
<strong>th</strong>e biodegradation kinetics such as enzyme <strong>ac</strong>tivity and substrate concentration. The yield<br />
coefficient might be high and yet <strong>th</strong>e enzyme <strong>ac</strong>tivity might be low, resulting in slow<br />
degradation rate. Sometimes <strong>th</strong>e degradation rate might be dependent upon substrate<br />
concentrations. Moreover, <strong>th</strong>e parameter group (µmax/(Y.Ks)) <strong>of</strong> yeast and b<strong>ac</strong>teria is 1.77 x<br />
10 -3 and 3.06 x 10 -3 L/mg.h, respectively, indicating <strong>th</strong>at <strong>th</strong>e biodegradation <strong>of</strong> organics by<br />
yeast is less <strong>th</strong>an <strong>th</strong>at <strong>of</strong> b<strong>ac</strong>teria. Comparison <strong>of</strong> biokinetic parameters wi<strong>th</strong> <strong>th</strong>e o<strong>th</strong>er<br />
le<strong>ac</strong>hate case studies and <strong>th</strong>e domestic wastewater is expressed in Table 4.2.<br />
Table 4.2 Biokinetic Coefficients <strong>of</strong> Yeast and B<strong>ac</strong>teria Sludge for <strong>th</strong>e Le<strong>ac</strong>hates<br />
Biokinetic parameters<br />
Type <strong>of</strong><br />
Sludge<br />
µmax<br />
(d -1 )<br />
Y<br />
(mgVSS/mgCOD)<br />
k<br />
(d -1 )<br />
µmax/Y.Ks<br />
(L/mg.h)<br />
Reference<br />
Yeast sludge 0.27 0.49 0.51 1.77 x 10 -3 Present study<br />
0.42 0.52 0.81 3.06 x 10 -3 Present study<br />
0.30 0.39 0.77 1.57 x 10<br />
0.45 0.63 0.71<br />
-3<br />
1.00 x 10 -3<br />
Zapf-Gilje and<br />
Mavinic, 1981<br />
0.23 0.50 0.46 1.06 x 10 -4 Gaudy, et al.,<br />
1986<br />
8.16 0.85 9.6 2.8 x 10<br />
0.12 0.67 0.18<br />
-4<br />
0.4 x 10 -4<br />
B<strong>ac</strong>teria<br />
sludge<br />
Pirbazari, et al.,<br />
1996<br />
0.56 0.36 1.56 1.06 x 10 -4 Chae, et al.,<br />
1999<br />
Domestic 6.00 0.60 2-10 2.08 x 10<br />
wastewater<br />
(0.4-0.8)<br />
-2 Grady, et al.,<br />
1999<br />
In bo<strong>th</strong> cases, <strong>th</strong>e maximum specific grow<strong>th</strong> rate (µmax) was found to be less <strong>th</strong>an <strong>th</strong>e<br />
domestic wastewater. This could be <strong>th</strong>e type <strong>of</strong> organisms prevailing in <strong>th</strong>e domestic<br />
wastewater is different from <strong>th</strong>at <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate. Though <strong>th</strong>e maximum specific rate<br />
differed from <strong>th</strong>at <strong>of</strong> <strong>th</strong>e domestic wastewater, <strong>th</strong>e yield coefficient <strong>of</strong> bo<strong>th</strong> yeast and<br />
b<strong>ac</strong>teria sludge were found to be in <strong>th</strong>e same range as domestic wastewater, while <strong>th</strong>e<br />
substrate utilization rate was lower <strong>th</strong>an <strong>th</strong>at <strong>of</strong> domestic wastewater. This might be due to<br />
74
change in <strong>th</strong>e predominant species while carbon assimilation metabolism wi<strong>th</strong> different<br />
substrates.<br />
The yield depends upon <strong>th</strong>e oxidation state <strong>of</strong> <strong>th</strong>e carbon sources and nutrient<br />
elements, degree <strong>of</strong> polymerization <strong>of</strong> <strong>th</strong>e substrate, pa<strong>th</strong>way <strong>of</strong> metabolism, grow<strong>th</strong> rate<br />
and o<strong>th</strong>er physical parameters <strong>of</strong> cultivation (Tchobanoglous, et al., 2003). The maximum<br />
yield coefficient <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial culture was found to be greater <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast<br />
culture signifies <strong>th</strong>at b<strong>ac</strong>terial grow<strong>th</strong> is more pronounced <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast culture.<br />
This is fur<strong>th</strong>er supported by <strong>th</strong>e evidence <strong>th</strong>at <strong>th</strong>e specific grow<strong>th</strong> rate <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial<br />
culture was 0.42 d -1 compared to <strong>th</strong>at <strong>of</strong> 0.27 d -1 <strong>of</strong> <strong>th</strong>e yeast culture.<br />
The grow<strong>th</strong> rate <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial culture was almost 1.53 times <strong>th</strong>e yeast culture at a<br />
maximum substrate concentration <strong>of</strong> around 40 mg/L COD. Such an observation is in<br />
<strong>ac</strong>cordance wi<strong>th</strong> <strong>th</strong>e biokinetic studies conducted by Dan (2002) in high saline wastewater,<br />
where <strong>th</strong>e yeast culture showed a lower yield coefficient and specific grow<strong>th</strong> rate in <strong>th</strong>e<br />
yeast system compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial system.<br />
4.2.3 Toxicity Studies<br />
In addition to many organic and inorganic compounds <strong>th</strong>at are present in <strong>th</strong>e landfill<br />
le<strong>ac</strong>hate, <strong>th</strong>e presence <strong>of</strong> toxic substances also persists. These toxic compounds not only<br />
pose harm to <strong>th</strong>e environment when released but also affect <strong>th</strong>e efficiency <strong>of</strong> <strong>th</strong>e biological<br />
treatment system. These metals affect <strong>th</strong>e performance <strong>of</strong> <strong>th</strong>e biore<strong>ac</strong>tors by inhibiting <strong>th</strong>e<br />
b<strong>ac</strong>terial grow<strong>th</strong>. Oxygen consumption in a biological system has been monitored in<br />
several studies to monitor <strong>th</strong>e toxicity <strong>of</strong> <strong>th</strong>e wastewater from several sources (Solyom, et<br />
al., 1976; Solyom, 1977). For an aerobic organism, toxicity test could be measured by<br />
measuring <strong>th</strong>e oxygen uptake rate (OUR) in presence <strong>of</strong> <strong>th</strong>e toxicant, which will signify <strong>th</strong>e<br />
inhibitory effect <strong>of</strong> <strong>th</strong>e toxicant on <strong>th</strong>e microorganism (Chen, et al., 1997).<br />
(1) Ammonia Toxicity<br />
The ammonium concentration in <strong>th</strong>e le<strong>ac</strong>hate is usually found to be very high. As<br />
mentioned by Keenan, et al. (1984), <strong>th</strong>e high concentration <strong>of</strong> ammonia is a challenge for<br />
<strong>th</strong>e biological treatment <strong>of</strong> le<strong>ac</strong>hate as it may brings about toxicity to <strong>th</strong>e organisms. For<br />
better understanding <strong>of</strong> <strong>th</strong>e effect <strong>of</strong> <strong>th</strong>e ammonia concentration on <strong>th</strong>e grow<strong>th</strong> <strong>of</strong> <strong>th</strong>e<br />
organisms used in <strong>th</strong>e present study, toxicity test was done wi<strong>th</strong> ammonium chloride as <strong>th</strong>e<br />
source <strong>of</strong> ammonia. The operational parameters for <strong>th</strong>e toxicity test are described in Table<br />
3.3. The procedure <strong>of</strong> toxicity test is described in section 3.4.1. The ammonium chloride<br />
concentration used in <strong>th</strong>e study were 70, 1000, 1500 and 2000 mg/L. The substrate<br />
concentration used in <strong>th</strong>e study was 7 mg COD/L for <strong>th</strong>e b<strong>ac</strong>terial system and 5.6 mg<br />
COD/L for <strong>th</strong>e yeast system.<br />
An aerobic biological process contains two major classes <strong>of</strong> aerobic microorganisms,<br />
namely nitrifying b<strong>ac</strong>teria and heterotrophic b<strong>ac</strong>teria. The heterotrophs represent <strong>th</strong>e<br />
microorganisms responsible for carbon<strong>ac</strong>eous removal. Nitrifying b<strong>ac</strong>teria (Nitrosomonas<br />
and Nitrob<strong>ac</strong>tor) are responsible for <strong>th</strong>e oxidation <strong>of</strong> ammonia to nitrite and nitrate<br />
nitrogen. The optimum pH is 7.5 to 8.6 for Nitrosomonas and 6.0 to 8.0 for Nitrob<strong>ac</strong>tor.<br />
The range <strong>of</strong> free ammonia concentration affecting to Nitrosomonas had been investigated<br />
by some researcher is around 7 to 150 mg/L and Nitrob<strong>ac</strong>tor is around 0.1 to 1.0 mg/L<br />
(Barnes, 1983; Abeling and Seyfried, 1992). It was observed by Blum and Speece (1992)<br />
75
<strong>th</strong>at <strong>th</strong>e nitrifying b<strong>ac</strong>teria are more sensitively inhibited by a given concentration <strong>of</strong><br />
chemical toxicant <strong>th</strong>an <strong>th</strong>e heterotrophic b<strong>ac</strong>teria. Thus, failure <strong>of</strong> <strong>th</strong>e nitrifying process<br />
would occur before <strong>th</strong>e carbon<strong>ac</strong>eous removal process. Blum and Speece (1992) also<br />
reported <strong>th</strong>at Nitrob<strong>ac</strong>tor exhibited approximately <strong>th</strong>e same toxicity as aerobic<br />
heterotrophs. Thus, to prevent <strong>th</strong>e interference <strong>of</strong> <strong>th</strong>e nitrifying system in <strong>th</strong>e toxicity test,<br />
70 mg/L <strong>of</strong> Nitrogen as NH3-N was added to suppress nitrification (Liebeskind, 1999) in<br />
<strong>th</strong>e b<strong>ac</strong>terial system.<br />
The major biokinetic parameters found in <strong>th</strong>e two systems namely, <strong>th</strong>e b<strong>ac</strong>terial and<br />
yeast sludge are expressed in Table 4.3 and 4.4, respectively. The concentration <strong>of</strong> free<br />
ammonia produced in <strong>th</strong>e system was also measured using a dissociation equation <strong>of</strong><br />
ammonium salt into ammonia and hydrogen ion (Ortiz, et al., 1997). The formulae used for<br />
measuring <strong>th</strong>e free ammonia in given below:<br />
[NH3-N] = 17 [NH4 + -N] 10 pH Eq. 4.1<br />
14 exp [ 6344 / ( 273 + T ) ] + 10 pH<br />
The inhibition was found to be much higher in <strong>th</strong>e b<strong>ac</strong>terial sludge <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e<br />
yeast sludge. The probable reason for <strong>th</strong>is could be <strong>th</strong>e low oxygen uptake <strong>of</strong> 0.0030 mg<br />
O2/mg VSS. h compared to <strong>th</strong>at 0.0078 mg O2/mg VSS. h <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial culture even at<br />
an ammonium chloride concentration <strong>of</strong> 70 mg/L. The complete biokinetic parameters<br />
measured for <strong>th</strong>e yeast and b<strong>ac</strong>terial system are presented in Table C-3 and C-4 <strong>of</strong><br />
Appendix C. The free ammonia nitrogen concentration in <strong>th</strong>e b<strong>ac</strong>terial sludge was found to<br />
re<strong>ac</strong>h a maximum <strong>of</strong> 20 mg/L whereas <strong>th</strong>at found in yeast sludge was 0.013 mg/L. It has<br />
been found <strong>th</strong>at <strong>th</strong>e ammonia concentration <strong>of</strong> 31 to 49 mg/L can cause toxicity (Cheung,<br />
et al., 1997) and at a concentration <strong>of</strong> 200 mg/L can adversely affects <strong>th</strong>e sludge properties<br />
(Robinson and Maris, 1985). The toxicity <strong>of</strong> <strong>th</strong>e compound also depends upon <strong>th</strong>e nature<br />
and <strong>th</strong>e composition <strong>of</strong> <strong>th</strong>e waste. This could be <strong>th</strong>e reason for relatively high toxicity <strong>of</strong><br />
<strong>th</strong>e ammonia in <strong>th</strong>e landfill le<strong>ac</strong>hate. In a yeast based biological system, it was found <strong>th</strong>at a<br />
free ammonia concentration <strong>of</strong> 11 mg/L would inhibit <strong>th</strong>e grow<strong>th</strong> <strong>of</strong> Candida utilis where<br />
<strong>th</strong>e ammonium nitrogen concentration was 350- 520 mg/L (Ortiz, et al., 1997). Relatively<br />
low toxicity in <strong>th</strong>e le<strong>ac</strong>hate studies could be attributed to <strong>th</strong>e low pH.<br />
Table 4.3 Effect <strong>of</strong> Free Ammonia Concentration on Yield Coefficient and <strong>th</strong>e Specific<br />
Grow<strong>th</strong> Rate <strong>of</strong> <strong>th</strong>e B<strong>ac</strong>terial Sludge<br />
NH4Cl<br />
(mg NH4-N/L)<br />
Free NH3<br />
(mg NH3-N/L)<br />
Y<br />
(mg VSS/mg COD)<br />
µ<br />
(d -1 )<br />
70 0.44-0.70 0.39 0.093<br />
1000 6.36-10.05 0.38 0.055<br />
1500 9.54-15.07 0.35 0.046<br />
2000 12.72-20.10 0.29 0.031<br />
76
Table 4.4 Effect <strong>of</strong> Free Ammonia Concentration on Yield Coefficient and <strong>th</strong>e Specific<br />
Grow<strong>th</strong> Rate <strong>of</strong> <strong>th</strong>e Yeast Sludge<br />
NH4Cl<br />
(mg NH4-N/L)<br />
Free NH3<br />
(mg NH3-N/L)<br />
Y<br />
(mg VSS/mg COD)<br />
µ<br />
(d -1 )<br />
70 0 0.50 0.095<br />
1000 0.003-0.006 0.49 0.089<br />
1500 0.005-0.010 0.48 0.087<br />
2000 0.006-0.013 0.49 0.090<br />
The inhibition <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and <strong>th</strong>e yeast culture wi<strong>th</strong> increasing concentration is<br />
expressed in Figure 4.9. The inhibition <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial culture increased from 27 to 37%<br />
wi<strong>th</strong> corresponding increase in ammonium chloride concentration from 1,000 to 2,000<br />
mg/L. The inhibition <strong>of</strong> <strong>th</strong>e yeast culture was found to be around 6% even at an ammonium<br />
chloride concentration <strong>of</strong> 2,000 mg/L.<br />
% Inhibition<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
Mixed b<strong>ac</strong>teria<br />
Mixed yeast<br />
R 2 = 0.9592<br />
Figure 4.9 Inhibition <strong>of</strong> <strong>th</strong>e Yeast and B<strong>ac</strong>terial Culture wi<strong>th</strong> Increasing Ammonium<br />
Chloride Concentration<br />
Ano<strong>th</strong>er reason <strong>th</strong>at would contribute to <strong>th</strong>e resistance <strong>of</strong> <strong>th</strong>e yeast sludge to <strong>th</strong>e<br />
ammonia toxicity could be <strong>th</strong>e ammonium and free ammonia concentration. It is well<br />
known <strong>th</strong>at <strong>th</strong>e molecular ammonia is toxic but not <strong>th</strong>e ammonium ion. The relationship<br />
between <strong>th</strong>e ammonium ion and ammonia is pH dependent. The ammonium ion in <strong>th</strong>e<br />
wastewater is usually is in equilibrium wi<strong>th</strong> <strong>th</strong>e ammonia and hydrogen ion concentration.<br />
The equation <strong>of</strong> which is expressed as follows:<br />
77<br />
R 2 = 0.9546<br />
0 500 1000 1500 2000 2500 3000 3500<br />
NH4Cl Concentration (mg/L)
NH3 + H + NH4 +<br />
At low pH, when H + is high, <strong>th</strong>e equilibrium shifts towards <strong>th</strong>e right direction. This<br />
results in low ammonia concentration. The low percentage inhibition in <strong>th</strong>e yeast system<br />
could be attributed to <strong>th</strong>is, as <strong>th</strong>e operation pH <strong>of</strong> <strong>th</strong>e yeast system is around 3.5 to 3.8<br />
compared to 6.8 to 7.0 in <strong>th</strong>e b<strong>ac</strong>terial sludge.<br />
Though, <strong>th</strong>e ammonia concentration did not affect <strong>th</strong>e yeast sludge much, it was<br />
found to inhibit <strong>th</strong>e microbial grow<strong>th</strong> in <strong>th</strong>e b<strong>ac</strong>terial system. As <strong>th</strong>e ammonium is present<br />
in high concentration in <strong>th</strong>e le<strong>ac</strong>hate, le<strong>ac</strong>hing becomes necessary prior to fur<strong>th</strong>er<br />
biological treatment. Thus, ammonia stripping was done to ensure better efficiency <strong>of</strong> <strong>th</strong>e<br />
biological system and prevent <strong>th</strong>e inhibition <strong>of</strong> <strong>th</strong>e toxic compounds to <strong>th</strong>e organisms.<br />
(2) Lead Toxicity<br />
Many researches have shown <strong>th</strong>e presence <strong>of</strong> toxic compounds in many landfill<br />
le<strong>ac</strong>hate (Brown and Donnelly, 1988; Baun, et al., 1999). O<strong>th</strong>er studies have shown <strong>th</strong>at<br />
le<strong>ac</strong>hate from a municipal solid waste landfill can be more toxic <strong>th</strong>an <strong>th</strong>e le<strong>ac</strong>hate from <strong>th</strong>e<br />
hazardous waste landfill (Brown and Donnelly, 1988; Schrab, et al., 1993; Clement, et al.,<br />
1996). Even <strong>th</strong>ough large scale disposal <strong>of</strong> hazardous toxic metals is no longer pr<strong>ac</strong>ticed,<br />
but small generators such as small businesses and households do continue to dispose<br />
hazardous chemicals in <strong>th</strong>e municipal landfills (Brown and Donnelly, 1988). One <strong>of</strong> such<br />
compounds is <strong>th</strong>e lead, which is present in <strong>th</strong>e landfill le<strong>ac</strong>hate. The source <strong>of</strong> lead is<br />
probably from plumbing fixtures in <strong>th</strong>e individual homes and o<strong>th</strong>er lead-containing<br />
products (such as leaded solder, battery, glass, PVC, and small lead items) which are<br />
disposed <strong>of</strong> as waste.<br />
Though, lead is found at a concentration lower <strong>th</strong>an 1 mg/L (Chian and DeWalle,<br />
1976; Ehrig, 1983; Keenan, et al., 1984; Robinson and Maris, 1985; Robinson, 1992), an<br />
increased concentration <strong>of</strong> <strong>th</strong>e lead can pose failure <strong>of</strong> <strong>th</strong>e biological systems. To find out<br />
<strong>th</strong>e effect <strong>of</strong> <strong>th</strong>e increasing lead concentration on <strong>th</strong>e <strong>ac</strong>tivated sludge, toxicity studies was<br />
done wi<strong>th</strong> it using lead nitrate as a lead source. The lead nitrate in <strong>th</strong>e b<strong>ac</strong>terial system was<br />
varied from 20-100 mg/L compared to 2-25 mg/L in <strong>th</strong>e yeast system. The lead nitrate used<br />
in <strong>th</strong>e yeast system was lower <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial system due to <strong>th</strong>e reason <strong>th</strong>at at<br />
lower pH, lead would easily dissociate as a free ion (Cui, et al., 2000). The lead toxicity<br />
was done as described in section 3.4.2. The biokinetic parameters for <strong>th</strong>e lead toxicity<br />
studies in b<strong>ac</strong>teria and yeast le<strong>ac</strong>hate is given in Table C-5 and C-6 <strong>of</strong> Appendices C. The<br />
substrate concentration in <strong>th</strong>e study was similar to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e ammonia toxicity study.<br />
The substrate utilization by <strong>th</strong>e yeast and b<strong>ac</strong>terial sludge is presented in Table 4.5. It<br />
is found <strong>th</strong>at <strong>th</strong>e substrate utilization <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial system is higher <strong>th</strong>an <strong>th</strong>at <strong>of</strong> yeast<br />
sludge. As <strong>th</strong>e soluble lead concentration increased from 0 to 10.98 mg/L, <strong>th</strong>e oxygen<br />
utilization rate decreased from 0.519 mg O2/mg VSS.h to 0.075 mg O2/mg VSS.h. The<br />
percentage inhibition at high concentration was found to be 85%. The inhibition effects <strong>of</strong><br />
<strong>th</strong>e lead on <strong>th</strong>e b<strong>ac</strong>terial and yeast system is expressed in Figure 4.10 and 4.11, respectively.<br />
78
Table 4.5 Substrate Utilization by <strong>th</strong>e Yeast and B<strong>ac</strong>terial Sludge<br />
B<strong>ac</strong>teria Yeast<br />
Soluble Pb in Oxygen Utilization Soluble Pb in Oxygen Utilization<br />
Sample (mg/L) (mg O2/mg VSS.h) Sample (mg/L) (mg O2/mg VSS.h)<br />
0.00 0.519 0.00 0.071<br />
2.38 0.233 1.15 0.042<br />
4.11 0.233 1.41 0.042<br />
5.23 0.158 1.98 0.032<br />
10.98 0.075 2.10 0.017<br />
% Inhibition .<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
0 2 4 6 8 10 12<br />
Concentration <strong>of</strong> Soluble Lead (mg/L)<br />
Figure 4.10 Inhibitory Effect <strong>of</strong> Lead in B<strong>ac</strong>terial Sludge<br />
The soluble lead concentration in <strong>th</strong>e yeast culture was from 0 to 2.10 mg/L<br />
concentration. The oxygen utilization rate <strong>of</strong> <strong>th</strong>e yeast sludge decreased from 0.071 to<br />
0.017 mg O2/mg VSS.h. The inhibition <strong>of</strong> <strong>th</strong>e yeast system was 76% at a soluble lead<br />
concentration <strong>of</strong> 2.10 mg/L. The percentage <strong>of</strong> inhibition <strong>of</strong> yeast sludge was comparable<br />
to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial sludge. The soluble lead concentration <strong>of</strong> 2.38 mg/L in <strong>th</strong>e b<strong>ac</strong>terial<br />
system showed 55% inhibition. In <strong>th</strong>e yeast system, 50% inhibition occurred at a soluble<br />
lead concentration <strong>of</strong> 1.50 mg/L. The toxicity effect is close to <strong>th</strong>at reported by Cui, et al.<br />
(2000), where it is said <strong>th</strong>at toxicity effect on yeast occurs at concentration <strong>of</strong> 1 mg/L.<br />
79
% Inhibition .<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
0.0 0.5 1.0 1.5 2.0 2.5<br />
Concentration <strong>of</strong> Soluble Lead (mg/L)<br />
Figure 4.11 Inhibition Effect <strong>of</strong> Lead in Yeast Sludge<br />
In <strong>th</strong>e b<strong>ac</strong>terial system, 50% inhibition occurred at a concentration approximately 3<br />
mg/L. The toxicity effects to bo<strong>th</strong> marine and freshwater invertebrates have been recorded<br />
at <strong>th</strong>e concentrations range between 0.5 and 5.0 mg/L (Oladimeji and Offem, 1989),<br />
whereas it was between 2 and 6 mg/L for <strong>th</strong>e <strong>ac</strong>tivated sludge process (Madoni, et al.,<br />
1996). Madoni, et al. (1999) also found <strong>th</strong>at <strong>th</strong>e microbial <strong>ac</strong>tivity in an <strong>ac</strong>tivated sludge<br />
plant treating wastewater containing 3.5 to 9.2 mg/L <strong>of</strong> soluble lead could be adversely<br />
affected. The higher concentrations <strong>of</strong> soluble lead applied in <strong>th</strong>e experiments point out <strong>th</strong>e<br />
higher resilience <strong>of</strong> b<strong>ac</strong>teria in <strong>th</strong>e presence <strong>of</strong> lead.<br />
4.3 Application <strong>of</strong> Yeast and B<strong>ac</strong>teria Based Membrane Biore<strong>ac</strong>tors in Le<strong>ac</strong>hate<br />
Treatment<br />
Landfill le<strong>ac</strong>hate treatment is a complex task due to <strong>th</strong>e highly variable waste<br />
landfilled, <strong>th</strong>e type and design <strong>of</strong> <strong>th</strong>e landfill, landfill age and climatic and seasonal<br />
variations in different regions. Hence, ra<strong>th</strong>er <strong>th</strong>an recommending treatment options based<br />
on specific f<strong>ac</strong>tors, it would be necessary to consider landfill age as a unique case.<br />
Medium-aged landfill le<strong>ac</strong>hate is char<strong>ac</strong>terized by a high COD and ammonia content wi<strong>th</strong><br />
a relatively lower BOD. Le<strong>ac</strong>hate treatment systems in recent years are sophisticated,<br />
reliable and are able to consistently treat le<strong>ac</strong>hate to keep up <strong>th</strong>e specific discharge<br />
standards (Robinson, 1999). One such treatment technique is <strong>th</strong>e membrane biore<strong>ac</strong>tors.<br />
Membrane re<strong>ac</strong>tor in recent years has been proved to be effective and economically<br />
feasible for treatment <strong>of</strong> various kinds <strong>of</strong> toxic wastewaters. Moreover, industrial<br />
utilization <strong>of</strong> <strong>th</strong>e MBR has worked successfully for treating complex wastes like landfill<br />
le<strong>ac</strong>hates and cosmetic wastewaters (Manem, 1993; Mandra, et al., 1995). In <strong>th</strong>e present<br />
study, initially performance <strong>of</strong> <strong>th</strong>e membrane biore<strong>ac</strong>tors have been evaluated wi<strong>th</strong>out any<br />
pre-treatment based on various f<strong>ac</strong>tors such as removal efficiency <strong>of</strong> TKN and COD,<br />
membrane fouling, etc.<br />
80
4.3.1 Initial Membrane Resistance<br />
Prior to starting up <strong>th</strong>e experiment, it is necessary to measure <strong>th</strong>e membrane<br />
resistance to understand <strong>th</strong>e filtration cap<strong>ac</strong>ity <strong>of</strong> <strong>th</strong>e membrane and <strong>th</strong>e change in <strong>th</strong>e<br />
resistance after fouling. The linear flux variation along wi<strong>th</strong> <strong>th</strong>e applied pressure was<br />
obtained by varying <strong>th</strong>e flow rate. The detailed experimental data is presented in Table D-1<br />
and D-2 <strong>of</strong> Appendix D for <strong>th</strong>e b<strong>ac</strong>terial based membrane biore<strong>ac</strong>tor (BMBR) and yeast<br />
based membrane biore<strong>ac</strong>tor (YMBR), respectively. The graph showing linear flux <strong>of</strong> <strong>th</strong>e<br />
membrane re<strong>ac</strong>tors are represented in Figure 4.12. Membrane permeate flux was measured<br />
by weighing permeate wi<strong>th</strong> <strong>th</strong>e electronic balance. Initial membrane resistance was<br />
determined from <strong>th</strong>e relationship between flux and applied pressure as follows:<br />
Pressure (kPa)<br />
Pressure (kPa)<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
Figure 4.12 Variation in Transmembrane Pressure wi<strong>th</strong> Permeate Flux (a) YMBR and<br />
(b) BMBR<br />
81<br />
y = 0.1609x + 1.0378<br />
R 2 = 0.9984<br />
0 50 100 150 200<br />
Flux (L/m 2 .h)<br />
(a)<br />
y = 0.1521x + 0.5234<br />
R 2 = 0.9988<br />
0 50 100 150 200<br />
Flux (L/m 2 .h)<br />
(b)
Where;<br />
J = ∆P Eq. 4.2<br />
µRt<br />
J = Permeate flux (L/m 2 .h)<br />
∆P = Applied pressure (kPa)<br />
µ = Dynamic viscosity (N.s/m 2 )<br />
Rt = Total resistance for filtration or Hydraulic resistance <strong>of</strong> clean<br />
membrane (m -1 )<br />
The membrane resistance (Rm) <strong>of</strong> <strong>th</strong>e YMBR was found to be 6.66 x 10 11 m -1 and<br />
<strong>th</strong>at <strong>of</strong> BMBR was found to be 6.29 x 10 11 m -1 . The membrane used in <strong>th</strong>e study had a<br />
surf<strong>ac</strong>e area <strong>of</strong> 0.42 m 2 and pore size <strong>of</strong> 0.1 µm. Bo<strong>th</strong> <strong>th</strong>e membranes had a similar pore<br />
size and almost <strong>th</strong>e same membrane resistance. The membrane resistant is important as<br />
wi<strong>th</strong> increasing membrane operation, <strong>th</strong>e membrane resistance tends to increase <strong>th</strong>e<br />
transmembrane pressure, which after a certain limit decreases <strong>th</strong>e flux to a great extent.<br />
During <strong>th</strong>is stage when <strong>th</strong>e transmembrane pressure re<strong>ac</strong>hes a maximum, <strong>th</strong>e membrane is<br />
said to be fouled. The effect <strong>of</strong> <strong>th</strong>e membrane resistance prior to and after fouling has also<br />
been studied which would be discussed in later part <strong>of</strong> <strong>th</strong>is chapter.<br />
4.3.2 Optimization <strong>of</strong> HRT in Terms <strong>of</strong> Membrane Biore<strong>ac</strong>tor Treatment Efficiency<br />
(1) COD Removal Efficiency<br />
The influent COD concentration was maintained around 7,000 to 9,000 mg/L, and<br />
<strong>th</strong>e volumetric loading rate was gradually increased from 6.7 to 17.9 kg COD/m 3 .d by<br />
decreasing HRT from 24 h to 12 h wi<strong>th</strong> 4 h decrement. A detailed tabulation <strong>of</strong> <strong>th</strong>e results<br />
is given in Table E-1 and E-2 <strong>of</strong> Appendix E for <strong>th</strong>e BMBR and YMBR systems,<br />
respectively. The increase in organic loading in terms <strong>of</strong> COD concentration and change in<br />
HRT is presented in Figure 4.13. As a real le<strong>ac</strong>hate from <strong>th</strong>e transfer station and sanitary<br />
landfill was used, fluctuations in <strong>th</strong>e feed could not be avoided. In all experimental runs,<br />
<strong>th</strong>e MLSS <strong>of</strong> bo<strong>th</strong> <strong>th</strong>e systems were maintained around 10,000 to 12,000 mg/L and DO<br />
concentration <strong>of</strong> above 2.0 mg/L. Figure 4.14 and 4.15 illustrates <strong>th</strong>e MLSS concentration<br />
and pH, respectively in bo<strong>th</strong> <strong>th</strong>e membrane biore<strong>ac</strong>tors. The fluctuations in <strong>th</strong>e pH <strong>of</strong> <strong>th</strong>e<br />
BMBR re<strong>ac</strong>tor could be due to <strong>th</strong>e products if <strong>th</strong>e degradation taking pl<strong>ac</strong>e wi<strong>th</strong>in <strong>th</strong>e<br />
system.<br />
While treating <strong>th</strong>e medium-aged landfill wi<strong>th</strong> membrane biore<strong>ac</strong>tors, <strong>th</strong>e effluent<br />
COD concentration fluctuated wi<strong>th</strong> <strong>th</strong>at <strong>of</strong> <strong>th</strong>e influent concentration. The influent and<br />
effluent COD concentration in <strong>th</strong>e BMBR and YMBR are presented in Figure 4.16. It was<br />
observed <strong>th</strong>at <strong>th</strong>e average COD removal efficiency <strong>of</strong> <strong>th</strong>e YMBR was slightly higher <strong>th</strong>an<br />
<strong>th</strong>at <strong>of</strong> <strong>th</strong>e BMBR for varied HRT, <strong>th</strong>ough <strong>th</strong>e difference was just marginal. The reason for<br />
<strong>th</strong>e increased run period at 16h HRT was <strong>th</strong>e absence <strong>of</strong> significant improvement in <strong>th</strong>e<br />
treatment performance in terms <strong>of</strong> COD removal. In a study conducted by Sun, et al., 2002<br />
found similar results. When an influent wastewater wi<strong>th</strong> 2,400 mg/L COD was treated<br />
using a submerged MBR, it was found <strong>th</strong>at a change in HRT from 3 to 6 days did not<br />
significantly affect <strong>th</strong>e performance. The removal efficiency just changed from 92 to 93%.<br />
A high COD removal <strong>of</strong> <strong>th</strong>e high streng<strong>th</strong> wastewater could be due to <strong>th</strong>e increased HRT<br />
82
when compared wi<strong>th</strong> <strong>th</strong>e present study. Figure 4.17 shows <strong>th</strong>e efficiency <strong>of</strong> COD removal<br />
for bo<strong>th</strong> YMBR and BMBR systems for various HRT <strong>th</strong>roughout <strong>th</strong>e run period.<br />
MLSS (mg/L)<br />
HRT (h)<br />
40<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
16000<br />
14000<br />
12000<br />
10000<br />
8000<br />
6000<br />
4000<br />
2000<br />
0<br />
HRT Organic Load<br />
1 22 48 72 94 119 145 173<br />
Time (days)<br />
Figure 4.13 Variation in Organic Load wi<strong>th</strong> HRT<br />
Figure 4.14 Variation in MLSS in <strong>th</strong>e MBR Systems<br />
83<br />
BMBR<br />
YMBR<br />
0 20 40 60 80 100 120 140 160 180<br />
Time (days)<br />
22<br />
18<br />
14<br />
10<br />
6<br />
COD Organic Load (kg/m 3 .d)
pH<br />
COD (mg/L)<br />
10<br />
9<br />
8<br />
7<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
0<br />
12000<br />
10000<br />
8000<br />
6000<br />
4000<br />
2000<br />
0 20 40 60 80 100 120 140 160 180<br />
Time (days)<br />
0<br />
Figure 4.15 Variation in pH in <strong>th</strong>e MBR Systems<br />
Figure 4.16 COD Concentration in <strong>th</strong>e Influent and Effluent in <strong>th</strong>e BMBR and YMBR<br />
at Different HRT<br />
84<br />
Feed BMBR YMBR<br />
1 22 48 72 94 119 145 173<br />
Time (days)<br />
Influent COD YMBR BMBR HRT<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
HRT (h)
COD Removal Efficiency<br />
(%)<br />
90<br />
80<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
BMBR YMBR<br />
0 20 40 60 80 100 120 140 160 180<br />
Time (days)<br />
Figure 4.17 COD Removal Efficiency in <strong>th</strong>e BMBR and YMBR at Different HRT<br />
The average COD removal efficiency in YMBR system was 63% when HRT<br />
ranged from 16 h to 24 h, whereas in BMBR system, <strong>th</strong>e average COD removal efficiency<br />
was 60% at HRT from 16 h to 24 h as listed in Table 4.6 and Table 4.7. When municipal<br />
wastewater wi<strong>th</strong> 300 mg/L COD was treated, a 97% <strong>of</strong> removal could be <strong>ac</strong>hieve (Fan, et<br />
al., 1996). At HRT <strong>of</strong> 12 h, <strong>th</strong>e average COD removal efficiency in YMBR and BMBR<br />
was to 60% and 51%, respectively. The decrease in removal efficiency in <strong>th</strong>e b<strong>ac</strong>terial<br />
system at a lower HRT was more apparent, which could be due to <strong>th</strong>e presence <strong>of</strong><br />
ammonia in <strong>th</strong>e le<strong>ac</strong>hate posing toxicity to <strong>th</strong>e b<strong>ac</strong>terial culture. This aspect is also<br />
supported by <strong>th</strong>e biokinetic studies, which states <strong>th</strong>at <strong>th</strong>e ammonia inhibits b<strong>ac</strong>terial cells to<br />
a greater extent <strong>th</strong>an <strong>th</strong>e yeast cells.<br />
The COD removal in 12 h HRT in bo<strong>th</strong> <strong>th</strong>e re<strong>ac</strong>tors was very low compared to <strong>th</strong>at in<br />
o<strong>th</strong>er HRTs. In addition to a better COD removal efficiency, YMBR was more stable <strong>th</strong>an<br />
BMBR. As, <strong>th</strong>e yeast system did not show a significant improvement compared to b<strong>ac</strong>teria<br />
in terms <strong>of</strong> COD removal, it could be suggested <strong>th</strong>at fur<strong>th</strong>er investigations are required to<br />
conclude.<br />
Table 4.6 COD Removal Efficiency in YMBR System at Different HRT<br />
Values<br />
COD Removal (%)<br />
HRT 24 h HRT 20 h HRT 16 h HRT 12 h<br />
Maximum 69 70 75 72<br />
Minimum 58 60 59 50<br />
Average 63 64 66 60<br />
Std. Dev. 4 4 6 8<br />
85<br />
26<br />
24<br />
22<br />
20<br />
18<br />
16<br />
14<br />
12<br />
10<br />
8<br />
HRT (h)
Table 4.7 COD Removal Efficiency in BMBR System at Different HRT<br />
Values<br />
COD Removal (%)<br />
HRT 24 h HRT 20 h HRT 16 h HRT 12 h<br />
Maximum 66 76 76 56<br />
Minimum 53 50 52 46<br />
Average 60 65 62 51<br />
Std. Dev. 6 9 6 4<br />
To fur<strong>th</strong>er verify <strong>th</strong>e treatability in <strong>th</strong>e yeast and b<strong>ac</strong>terial system, <strong>th</strong>e F/M ratio and<br />
<strong>th</strong>e COD removal wi<strong>th</strong> MLSS were compared. Figure 4.18 represents <strong>th</strong>e organic removal<br />
wi<strong>th</strong> variation in F/M ratio. It indicated <strong>th</strong>at while comparing <strong>th</strong>e BMBR, YMBR obtained<br />
higher specific COD removal rate at F/M ratio greater <strong>th</strong>an 0.85 mg COD/mg SS.d. It also<br />
showed <strong>th</strong>at <strong>th</strong>e COD removal rate <strong>of</strong> YMBR is higher <strong>th</strong>an <strong>th</strong>at <strong>of</strong> BMBR at <strong>th</strong>e same F/M<br />
ratio. Thus, it could be said <strong>th</strong>at <strong>th</strong>ough <strong>th</strong>e performance in terms <strong>of</strong> removal efficiency<br />
cannot be compared, in terms <strong>of</strong> total organic removal for available biomass in <strong>th</strong>e YMBR<br />
system is better.<br />
COD Removal Rate<br />
(mg COD/mg SS.d)<br />
1.20<br />
1.00<br />
0.80<br />
0.60<br />
0.40<br />
0.20<br />
0.00<br />
BMBR YMBR<br />
Figure 4.18 Variations in COD Removal Rate as a Function <strong>of</strong> F/M Ratio<br />
As <strong>th</strong>e loading rate was progressively increased <strong>th</strong>rough different stages, COD in <strong>th</strong>e<br />
effluent in <strong>th</strong>e yeast ranged from 1,860 to 4,270 mg/L and from 1,765 to 4,560 mg/L in <strong>th</strong>e<br />
b<strong>ac</strong>terial system.<br />
86<br />
YMBR:<br />
BMBR:<br />
y = 0.5993Ln(x) + 0.6183<br />
R 2 y = 0.7156Ln(x) + 0.6578<br />
R<br />
= 0.937<br />
2 = 0.8766<br />
0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80<br />
F/M Ratio (d -1 )
(2) TKN Removal Efficiency<br />
Prior to optimizing <strong>th</strong>e HRT in <strong>th</strong>e MBR systems, TKN removal in <strong>th</strong>e le<strong>ac</strong>hate was<br />
also studied. A TKN concentration <strong>of</strong> about 2,000 mg/L was used. The graph showing<br />
influent and effluent TKN concentration in <strong>th</strong>e BMBR and YMBR systems are presented<br />
in Figure E-1 <strong>of</strong> Appendix E. For <strong>th</strong>e yeast system, <strong>th</strong>e pH range was controlled around 3.6,<br />
to enhance yeast grow<strong>th</strong> and prevent b<strong>ac</strong>terial contamination. In <strong>th</strong>e <strong>ac</strong>idic pH, <strong>th</strong>e<br />
ammonium compounds tend to remain in <strong>th</strong>e form <strong>of</strong> ammonium ion ra<strong>th</strong>er <strong>th</strong>an as<br />
ammonia. Thus, it could be said <strong>th</strong>at <strong>th</strong>e free ammonia concentration in <strong>th</strong>e YMBR would<br />
be less <strong>th</strong>an 1.0 mg/L. The free ammonia in <strong>th</strong>e BMBR was around 12 to 20 mg/L (Section<br />
4.2.3) due to <strong>th</strong>e pH range 6.8-7.0.<br />
Figure 4.19 shows TKN removal efficiency for bo<strong>th</strong> YMBR and BMBR systems at<br />
different HRT. There was not any significant difference, <strong>th</strong>ough <strong>th</strong>e YMBR was<br />
marginally better <strong>th</strong>an BMBR. Average TKN removal efficiency in YMBR and BMBR<br />
systems was from 19% to 29% and 14% to 25%, respectively as given in Table 4.8 and 4.9.<br />
At a HRT <strong>of</strong> 12 h, <strong>th</strong>e average TKN removal efficiency in YMBR and BMBR was as low<br />
as 18% and 14%, respectively, similar to low COD removal.<br />
TKN Removal (%) .<br />
100<br />
90<br />
80<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
BMBR HRT YMBR<br />
1 22 48 72 94 119 145 173<br />
Time (days)<br />
Figure 4.19 TKN Removal Efficiency in <strong>th</strong>e YMBR and BMBR wi<strong>th</strong> HRT<br />
87<br />
24<br />
22<br />
20<br />
18<br />
16<br />
14<br />
12<br />
10<br />
HRT (h)
Table 4.8 TKN Removal Efficiency in YMBR System<br />
HRT (h)<br />
24<br />
TKN Removal (%)<br />
20 16 12<br />
Maximum 28 20 36 23<br />
Minimum 28 18 15 11<br />
Average 28 19 29 18<br />
Std. Dev. 0 1 7 5<br />
Table 4.9 TKN Removal Efficiency in BMBR System<br />
HRT (h)<br />
24<br />
TKN Removal (%)<br />
20 16 12<br />
Maximum 26 35 35 19<br />
Minimum 24 13 15 10<br />
Average 25 22 25 14<br />
Std. Dev 1 10 6 3<br />
Along wi<strong>th</strong> TKN Removal, <strong>th</strong>e total ammonium content was also measured. The<br />
influent ammonium concentration was around 1,700 mg/L. The ammoni<strong>ac</strong>al nitrogen<br />
contributed to about 85% and above <strong>of</strong> <strong>th</strong>e total organic nitrogen. The effluent ammonium<br />
concentration in <strong>th</strong>e YMBR and BMBR systems was 1,235 and 1,285 mg/L, respectively.<br />
The ammonium removal concentration was also found to be very low wi<strong>th</strong> 18% and 20%<br />
in <strong>th</strong>e BMBR and YMBR system, respectively. The ammonium concentration contributed<br />
to 85-90% <strong>of</strong> <strong>th</strong>e total nitrogen. The nitrite and nitrate concentrations (NO2 - and NO3 - ) in<br />
bo<strong>th</strong> YMBR and BMBR effluents were found to be very low. NO2 - and NO3 - concentration<br />
in <strong>th</strong>e YMBR and BMBR effluent ranged from 0.8 to 6.4 mg/L and less <strong>th</strong>an 1.0 mg/L,<br />
respectively. The probable reason for <strong>th</strong>e absence <strong>of</strong> a notable range <strong>of</strong> nitrate and nitrite<br />
could be due to <strong>th</strong>e absence <strong>of</strong> nitrifying b<strong>ac</strong>teria, namely <strong>th</strong>e Nitrosomonas and<br />
Nitrob<strong>ac</strong>ter. The inhibition <strong>of</strong> Nitrosomonas could be due to <strong>th</strong>e free ammonia present in<br />
le<strong>ac</strong>hate as suggested by many researchers, <strong>th</strong>at around 7 to 150 mg/L would affect <strong>th</strong>e<br />
Nitrosomonas and a concentration <strong>of</strong> around 0.1 to 1.0 mg/L would affect <strong>th</strong>e Nitrob<strong>ac</strong>ter<br />
(Barnesand and Bliss, 1983; Abeling and Seyfried, 1992). This would have <strong>th</strong>erefore<br />
affected <strong>th</strong>e nitrification process, as a result <strong>of</strong> which, <strong>th</strong>e le<strong>ac</strong>hate should be pre-treated to<br />
reduce ammonia concentration.<br />
Along wi<strong>th</strong> <strong>th</strong>e nitrogen content, <strong>th</strong>e phosphorus content in <strong>th</strong>e le<strong>ac</strong>hate was also<br />
measured. The average phosphorus concentration found in <strong>th</strong>e le<strong>ac</strong>hate was 68 mg/L. The<br />
COD: P ratio was also calculated to find out <strong>th</strong>e nutrient deficiency in <strong>th</strong>e le<strong>ac</strong>hate. The<br />
COD: P ratio in <strong>th</strong>e le<strong>ac</strong>hate was 100:0.85. Though, <strong>th</strong>e le<strong>ac</strong>hate was said to be marginally<br />
phosphorus deficient, it did not adversely affect <strong>th</strong>e COD removal efficiency in <strong>th</strong>e MBR<br />
systems. This was tested wi<strong>th</strong> and wi<strong>th</strong>out addition <strong>of</strong> polyphosphate in <strong>th</strong>e treatment<br />
system. Fur<strong>th</strong>er, many biological treatment systems have been used for treating le<strong>ac</strong>hate<br />
even wi<strong>th</strong> a COD:P as low as 100.02 (Pohland and Harper, 1985). The phosphate removal<br />
in bo<strong>th</strong> <strong>th</strong>e re<strong>ac</strong>tors was approximately 50%.<br />
During <strong>th</strong>e operation <strong>of</strong> membrane biore<strong>ac</strong>tors, a frequent problem f<strong>ac</strong>ed was<br />
foaming. Antifoam addition was used to prevent foam development (Praet, et al., 2001).<br />
88
As <strong>th</strong>ere was no significant improvement when <strong>th</strong>e HRT was increased from 16 to 24<br />
h in terms <strong>of</strong> COD removal, fur<strong>th</strong>er investigations were done at <strong>th</strong>ese two HRT, wi<strong>th</strong> 16 h<br />
HRT followed by 24 h HRT.<br />
4.3.3 Membrane Fouling and Membrane Resistance<br />
The membrane fouling is <strong>th</strong>e result <strong>of</strong> <strong>ac</strong>cumulation <strong>of</strong> rejected particles on <strong>th</strong>e top <strong>of</strong><br />
<strong>th</strong>e membrane (external fouling), or deposition and adsorption <strong>of</strong> small particles or<br />
m<strong>ac</strong>romolecules at <strong>th</strong>e pores or wi<strong>th</strong>in <strong>th</strong>e internal pore structure (internal fouling) <strong>of</strong> <strong>th</strong>e<br />
membrane (Guell, et al., 1999). The processes <strong>th</strong>at contribute to <strong>th</strong>e fouling are varied.<br />
They include adhesion <strong>of</strong> <strong>th</strong>e colloidal matters and m<strong>ac</strong>romolecules on <strong>th</strong>e external and<br />
internal surf<strong>ac</strong>e, grow<strong>th</strong> and adhesion <strong>of</strong> bi<strong>of</strong>ilms on <strong>th</strong>e membrane surf<strong>ac</strong>e, precipitation<br />
<strong>of</strong> solved matters, aging <strong>of</strong> <strong>th</strong>e membrane, etc (Gunder, 2001). Because <strong>of</strong> <strong>th</strong>e complex and<br />
diverse relationships, it is not possible to localize and define fouling clearly. The adverse<br />
effects <strong>of</strong> <strong>th</strong>e membrane fouling is <strong>th</strong>e reduction <strong>of</strong> <strong>th</strong>e permeate flux.<br />
In <strong>th</strong>e present study, a constant flux was maintained in <strong>th</strong>e membrane biore<strong>ac</strong>tors.<br />
The resistance <strong>of</strong> <strong>th</strong>e membrane influences <strong>th</strong>e permeate flux. To maintain a constant flux,<br />
<strong>th</strong>e flow rate was increased correspondingly by adjusting <strong>th</strong>e suction pump. The rapid<br />
membrane fouling is indicated by a sudden increase in <strong>th</strong>e transmembrane pressure. As a<br />
high transmembrane pressure is a result <strong>of</strong> <strong>th</strong>e membrane fouling process, it was used as a<br />
parameter indicating requirement <strong>of</strong> cleaning. The membrane in <strong>th</strong>e membrane re<strong>ac</strong>tors<br />
were cleaned when <strong>th</strong>e transmembrane pressure difference increased significantly. The<br />
membranes were cleaned before it re<strong>ac</strong>hed <strong>th</strong>e maximum pressure to prevent damage to <strong>th</strong>e<br />
membrane operation. The transmembrane pressure difference <strong>of</strong> <strong>th</strong>e YMBR and BMBR<br />
systems is given in Figure 4.20. The detailed results are given in Table E-3 and E-4 <strong>of</strong><br />
Appendix E. Though <strong>th</strong>e two re<strong>ac</strong>tors, wi<strong>th</strong> b<strong>ac</strong>terial and yeast culture did not show much<br />
difference in <strong>th</strong>e performance, <strong>th</strong>e yeast re<strong>ac</strong>tor showed an added advantage <strong>of</strong> lower<br />
membrane fouling and <strong>th</strong>us, longer membrane life.<br />
The cleaning was done by first flushing <strong>th</strong>e membrane wi<strong>th</strong> tap water to remove <strong>th</strong>e<br />
cake layer from <strong>th</strong>e membrane surf<strong>ac</strong>e. Later, a 3% sodium hydroxide solution was filtered<br />
<strong>th</strong>rough <strong>th</strong>e membrane and <strong>th</strong>en, washed wi<strong>th</strong> tap water. Finally, 1% solution <strong>of</strong> nitric <strong>ac</strong>id<br />
was filtered <strong>th</strong>rough <strong>th</strong>e membrane followed by tap water. This cycle was repeated until<br />
<strong>th</strong>e membrane resistance was almost equal to <strong>th</strong>e initial membrane resistance.<br />
The frequency <strong>of</strong> cleaning was greater in b<strong>ac</strong>terial membrane biore<strong>ac</strong>tor <strong>th</strong>an <strong>th</strong>e<br />
yeast membrane biore<strong>ac</strong>tor. The frequency <strong>of</strong> membrane fouling is presented in <strong>th</strong>e Table<br />
4.10 for bo<strong>th</strong> <strong>th</strong>e systems. The membrane resistance after cleaning is presented in Table<br />
4.11. The detailed calculation is summarized in Table D-3 and D-4 and Figure D-1 and D-<br />
2 <strong>of</strong> Appendix D. The b<strong>ac</strong>terial system was first cleaned after 63 days <strong>of</strong> operation while<br />
<strong>th</strong>e yeast based system was cleaned after 80 days. It could be said <strong>th</strong>at <strong>th</strong>e membrane wi<strong>th</strong><br />
yeast re<strong>ac</strong>tor could be operated 27% more <strong>th</strong>an <strong>th</strong>e b<strong>ac</strong>terial system. Fur<strong>th</strong>er, in a total <strong>of</strong><br />
181 days <strong>of</strong> operation <strong>of</strong> <strong>th</strong>e MBR systems, <strong>th</strong>e BMBR was cleaned five times compared to<br />
<strong>th</strong>ree times in <strong>th</strong>e YMBR system. The operating time <strong>of</strong> <strong>th</strong>e yeast membrane was about 1.3<br />
times longer <strong>th</strong>an <strong>th</strong>e b<strong>ac</strong>teria membrane.<br />
89
Trans-membrane Pressure<br />
(kPa)<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
YMBR<br />
BMBR<br />
HRT<br />
0 20 40 60 80 100 120 140 160 180<br />
Time (day)<br />
Figure 4.20 Cleaning <strong>of</strong> membranes in <strong>th</strong>e YMBR and BMBR system in relation to TMP<br />
Table 4.10 Membrane Cleaning Frequency in <strong>th</strong>e MBR Systems<br />
Membrane Cleaning<br />
Days after Membrane Operation<br />
BMBR YMBR<br />
1 63 80<br />
2 85 101<br />
3 126 154<br />
4 143 -<br />
5 167 -<br />
Table 4.11 Membrane Resistance in <strong>th</strong>e MBR Systems<br />
Membrane Resistance (m -1 Cleaning Frequency<br />
) after Cleaning<br />
BMBR YMBR<br />
Initial 6.29×10 11 6.66×10 11<br />
1 1.79×10 12 5.64×10 11<br />
2 1.02×10 12 3.31×10 12<br />
3 1.13×10 12 1.31×10 12<br />
4 2.81×10 12 -<br />
90<br />
26<br />
22<br />
18<br />
14<br />
10<br />
HRT (h)
The probable reason for frequent fouling in b<strong>ac</strong>terial system <strong>th</strong>an yeast system could<br />
be EPS formation. The EPS formation in re<strong>ac</strong>tor was greater in b<strong>ac</strong>terial system <strong>th</strong>an in <strong>th</strong>e<br />
yeast system. The mechanism <strong>of</strong> bi<strong>of</strong>ilm development in <strong>th</strong>e YMBR is different from <strong>th</strong>at<br />
<strong>of</strong> <strong>th</strong>e BMBR. In <strong>th</strong>e YMBR, <strong>th</strong>e yeasts att<strong>ac</strong>h itself physically to <strong>th</strong>e membrane surf<strong>ac</strong>e<br />
during filtration instead <strong>of</strong> getting trapped in a matrix as <strong>th</strong>e b<strong>ac</strong>terial cell. The yeast cells<br />
usually att<strong>ac</strong>h toge<strong>th</strong>er by means <strong>of</strong> physical interwinding <strong>of</strong> mycelia or pseudomycelia<br />
(Nishihara ESRC Ltd., 2001).<br />
Ano<strong>th</strong>er probable reason for frequent fouling in <strong>th</strong>e b<strong>ac</strong>terial based membrane<br />
biore<strong>ac</strong>tor could be <strong>th</strong>e size and nature <strong>of</strong> b<strong>ac</strong>terial cells in comparison wi<strong>th</strong> <strong>th</strong>e yeast cells.<br />
The b<strong>ac</strong>terial cells have a size <strong>of</strong> 0.5 to 1.0 µm diameter for <strong>th</strong>e spherical shaped, and 0.5<br />
to 1.0 µm wide and 1.5 to 3.0 µm long for <strong>th</strong>e cylindrical (rods) shaped b<strong>ac</strong>teria whereas<br />
<strong>th</strong>e size <strong>of</strong> yeast is around 5 to 30 µm leng<strong>th</strong> and 1 to 5µm wid<strong>th</strong>. The large yeast cells are<br />
said to form a dynamic membrane on <strong>th</strong>e top <strong>of</strong> <strong>th</strong>e original membrane <strong>th</strong>at is capable <strong>of</strong><br />
entrapping some <strong>of</strong> <strong>th</strong>e protein aggregates. This may enhance <strong>th</strong>e recovery <strong>of</strong> <strong>th</strong>e viscous<br />
aggregates and <strong>th</strong>us slowing down <strong>th</strong>e fouling layer on <strong>th</strong>e surf<strong>ac</strong>e <strong>of</strong> <strong>th</strong>e primary<br />
membrane. Thus, <strong>th</strong>e yeast inter<strong>ac</strong>tions slow down <strong>th</strong>e pore blocking by capturing a<br />
significant fr<strong>ac</strong>tion <strong>of</strong> protein aggregates (Guell, et al., 1999). In addition to <strong>th</strong>is low<br />
operating pH, poor adhesion cap<strong>ac</strong>ity and low viscosity could be o<strong>th</strong>er reasons for low<br />
fouling frequency in <strong>th</strong>e yeast based MBR systems (Dan, 2002). Thus, yeast sludge can<br />
reduce membrane fouling rate more significantly <strong>th</strong>an <strong>th</strong>e b<strong>ac</strong>terial sludge. Therefore, it<br />
could be suggested <strong>th</strong>at <strong>th</strong>e use <strong>of</strong> yeast system in <strong>th</strong>e membrane biore<strong>ac</strong>tor could be<br />
beneficial as it has <strong>th</strong>e potential to reduce <strong>th</strong>e operating and maintenance costs <strong>of</strong> <strong>th</strong>e<br />
treatment system.<br />
4.4 Application <strong>of</strong> Yeast and B<strong>ac</strong>teria Based Membrane Biore<strong>ac</strong>tors in Ammonia<br />
Stripped Le<strong>ac</strong>hate Treatment<br />
Le<strong>ac</strong>hate wi<strong>th</strong> high load <strong>of</strong> refr<strong>ac</strong>tory compounds, low value <strong>of</strong> BOD/COD ratio,<br />
heavy metals and high concentration <strong>of</strong> nitrogen compounds, especially ammoni<strong>ac</strong>al<br />
exhibit difficulty in treatment (Dichtl, et al., 1997). Biological treatment becomes difficult<br />
when <strong>th</strong>e regarded le<strong>ac</strong>hate is inhibitive, toxic and older-less biodegradable (Geenens, et<br />
al., 1999). Due to <strong>th</strong>e presence <strong>of</strong> high ammonium content in <strong>th</strong>e le<strong>ac</strong>hate, it could be<br />
suggested <strong>th</strong>at removal <strong>of</strong> ammonium is required prior to biological membrane treatment.<br />
4.4.1 Ammonia Stripping Studies<br />
The toxicity <strong>of</strong> ammonia-bearing waste to b<strong>ac</strong>teria, algae, zooplankton and fish is a<br />
universal phenomenon. Ammonia has been shown to be toxic in oxidation ponds where<br />
high free ammonia and pH inhibit photosyn<strong>th</strong>esis (Abeliovich and Azov, 1976). The<br />
<strong>ac</strong>tivated sludge process has also been shown to fail due to <strong>th</strong>e ammonia toxicity and<br />
phosphorous limitation (Keenan, et al., 1984). In addition, Cheung, et al. (1993) <strong>th</strong>rough<br />
algal toxicity suggested <strong>th</strong>at ammonia concentration as ammoni<strong>ac</strong>al nitrogen is a major<br />
f<strong>ac</strong>tor governing <strong>th</strong>e toxicity <strong>of</strong> landfill le<strong>ac</strong>hate. Along wi<strong>th</strong> <strong>th</strong>is, it was difficult to<br />
overcome <strong>th</strong>e ammonia toxicity and to treat <strong>th</strong>e le<strong>ac</strong>hate containing a low COD/N ratio<br />
wi<strong>th</strong> biological process (Keenan, et al., 1984; Robinson and Maris, 1985; Cheung, et al.,<br />
1997). Therefore, <strong>th</strong>ere is a need to reduce <strong>th</strong>e concentration <strong>of</strong> ammonia in <strong>th</strong>e le<strong>ac</strong>hate<br />
below inhibitory level for <strong>th</strong>e success <strong>of</strong> biological systems in proper le<strong>ac</strong>hate treatment.<br />
As ammonia stripping is simple and less expensive <strong>th</strong>an o<strong>th</strong>er physico-chemical me<strong>th</strong>ods<br />
91
available, and appears to be cost effective pretreatment option for landfill le<strong>ac</strong>hate (Cheung,<br />
et al., 1997), it was used in <strong>th</strong>e present studies.<br />
The initial ammoni<strong>ac</strong>al nitrogen in <strong>th</strong>e simulated landfill le<strong>ac</strong>hate proposed in <strong>th</strong>e<br />
study was around 1,600-1,800 mg/L. Ammonia stripping studies were done in two stages-<br />
one in <strong>th</strong>e laboratory scale to optimize <strong>th</strong>e parameters to be used for ammonia studies prior<br />
to MBR process and secondly, in <strong>th</strong>e pilot scale studies to confirm <strong>th</strong>e results <strong>of</strong> <strong>th</strong>e<br />
laboratory studies in a larger scale. The laboratory scale studies were done wi<strong>th</strong> le<strong>ac</strong>hate<br />
volume <strong>of</strong> 2 L whereas pilot scale studies were done wi<strong>th</strong> le<strong>ac</strong>hate volume <strong>of</strong> 40 L.<br />
Firstly, <strong>th</strong>e pH for <strong>th</strong>e ammonia stripping was standardized using a velocity gradient<br />
<strong>of</strong> 1,530 s -1 wi<strong>th</strong> a cont<strong>ac</strong>t time <strong>of</strong> 2 h. The alkaline pH f<strong>ac</strong>ilitates <strong>th</strong>e formation <strong>of</strong> <strong>th</strong>e free<br />
ammonia molecule in comparison wi<strong>th</strong> <strong>th</strong>e ammonium ion, <strong>th</strong>us making it easy to remove<br />
ammonia. For <strong>th</strong>is reason, <strong>th</strong>e pH was adjusted to alkaline condition. The pH was adjusted<br />
to 9, 10, 11, and 12 using sodium hydroxide solution. The variation in removal efficiency<br />
was tested for <strong>th</strong>ree samples wi<strong>th</strong> different concentrations to eliminate <strong>th</strong>e standard error in<br />
<strong>th</strong>e analysis. It was found <strong>th</strong>at <strong>th</strong>e ammonia removal efficiency significantly increased<br />
when pH was increased from 10 to 11 or 12. The detailed results are presented in Table F-1<br />
<strong>of</strong> Appendix F. The removal efficiency was 38-45 % at pH 11 compared to 16-23% at pH<br />
9 and 24-30% at pH 10 (Figure 4.21). The difference between <strong>th</strong>e removal efficiency at pH<br />
11 and 12 was around 5%, which was considered not much significant. Thus, it could be<br />
said <strong>th</strong>at <strong>th</strong>e effective pH for <strong>th</strong>e ammonia stripping would be around 11-12. The results <strong>of</strong><br />
ammonia stripping were similar to o<strong>th</strong>er studies done in municipal landfill le<strong>ac</strong>hate<br />
(Cheung, et al., 1997; Ozturk, et al., 1999).<br />
After standardization <strong>of</strong> pH, <strong>th</strong>e velocity gradient and <strong>th</strong>e cont<strong>ac</strong>t time were<br />
standardized using le<strong>ac</strong>hate samples wi<strong>th</strong> pH 11-12. The ammonia concentration and<br />
removal efficiency at different cont<strong>ac</strong>t time and <strong>th</strong>e velocity gradients are given in <strong>th</strong>e<br />
Table F-2 to F-4 <strong>of</strong> Appendix F. The cont<strong>ac</strong>t time for <strong>th</strong>e ammonia removal was varied<br />
from 2 to 6 h. The velocity gradient used in <strong>th</strong>e study was 1,530, 2,850 and 4,330 s -1 ,<br />
which were varied along wi<strong>th</strong> <strong>th</strong>e cont<strong>ac</strong>t time. Figure 4.22 elaborates <strong>th</strong>e removal<br />
efficiency and ammonia concentration wi<strong>th</strong> varying cont<strong>ac</strong>t time and velocity gradient for<br />
<strong>th</strong>e initial le<strong>ac</strong>hate ammonia concentration <strong>of</strong> 1, 380 mg/L.<br />
The summary <strong>of</strong> <strong>th</strong>e results for different samples at varied cont<strong>ac</strong>t time and velocity<br />
gradient is summarized in Table 4.12. The rate <strong>of</strong> ammonia removal is directly<br />
proportional to <strong>th</strong>e velocity gradient or <strong>th</strong>e volume <strong>of</strong> air diffused <strong>th</strong>rough <strong>th</strong>e liquid. The<br />
main mechanism used for ammonia removal was simple mechanical mixing. It was found<br />
<strong>th</strong>at when <strong>th</strong>e velocity gradient was increased from 2,850 s -1 to 4,330 s -1 , <strong>th</strong>e removal<br />
efficiency did not improve much wi<strong>th</strong> 2, 4 and 6 h cont<strong>ac</strong>t time. Therefore, it could be<br />
concluded <strong>th</strong>at 2,850 s -1 was <strong>th</strong>e optimum velocity gradient for ammonia stripping. The<br />
ammonia removal efficiency was found to be between 88 and 95% at 4 h cont<strong>ac</strong>t time at<br />
velocity gradient <strong>of</strong> 2,850 s -1 . Though at 6 h cont<strong>ac</strong>t time, <strong>th</strong>e ammonia removal efficiency<br />
improved fur<strong>th</strong>er, <strong>th</strong>e difference in ammonia removal between 4 and 6 h was not<br />
significant. Thus, <strong>th</strong>e standard velocity gradient and <strong>th</strong>e cont<strong>ac</strong>t time were taken as 2,850<br />
s -1 and 4 h, respectively. At optimum conditions, <strong>th</strong>e system consumed NaOH <strong>of</strong> 12.5<br />
kg/m 3 and produced sludge at a rate <strong>of</strong> 80-100 L/m 3 .<br />
92
Ammonia Concentration<br />
(mg/L)<br />
Ammonia Removal<br />
(%)<br />
1600<br />
1400<br />
1200<br />
1000<br />
Figure 4.21 Variation in <strong>th</strong>e Ammonia Removal Efficiency wi<strong>th</strong> pH<br />
800<br />
600<br />
400<br />
200<br />
0<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
1,106 mg/L<br />
1,366 mg/L<br />
1,380 mg/L<br />
0 1 2 3<br />
Cont<strong>ac</strong>t Time (h)<br />
4 5 6<br />
Figure 4.22 Ammonia Removal Efficiency wi<strong>th</strong> Varying Velocity Gradient and pH<br />
93<br />
R 2 = 0.9753<br />
8 9 10 11 12 13<br />
pH<br />
100<br />
90<br />
80<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
Control 1530 s-1 2850 s-1 4330 s-1<br />
Removal Effeciency<br />
(%)
Table 4.12 Variation in Ammonia Removal Efficiency<br />
Velocity Gradient<br />
(s<br />
Ammonia Removal (%)<br />
Cont<strong>ac</strong>t Time (h)<br />
-1 )<br />
2 4 6<br />
0 28-31 37-46 47-51<br />
1,530 61-66 84-86 88-93<br />
2,850 69-74 88-95 96-98<br />
4,330 71-76 89-95 96-98<br />
While Diamadopoulos, 1994 did <strong>th</strong>e ammonia removal experiments using air<br />
stripping at pH 11.5 wi<strong>th</strong> air flow rate 2-3.5 L air/L in le<strong>ac</strong>hate, he could <strong>ac</strong>hieve 95%<br />
ammonia removal after a time period <strong>of</strong> 24 h. The removal efficiency <strong>of</strong> air stripping was<br />
similar wi<strong>th</strong> <strong>th</strong>e present study, wi<strong>th</strong> <strong>th</strong>e advantage <strong>th</strong>at <strong>th</strong>e present study required a lower<br />
time period. The main role <strong>of</strong> agitation was to create turbulence sufficient enough in <strong>th</strong>e<br />
free le<strong>ac</strong>hate surf<strong>ac</strong>e, to increase <strong>th</strong>e surf<strong>ac</strong>e area for ammonia removal (Smi<strong>th</strong> and Arab,<br />
1988). In <strong>th</strong>is case, <strong>th</strong>e ammonia desorption would be less important <strong>th</strong>an <strong>th</strong>e surf<strong>ac</strong>e area<br />
similar to studies done by Cheung, et al. (1997). This could be <strong>th</strong>e probable reason for <strong>th</strong>e<br />
efficient removal at a lower cont<strong>ac</strong>t time. Ano<strong>th</strong>er added advantage is <strong>th</strong>at <strong>th</strong>e present<br />
process can wi<strong>th</strong>stand changes in <strong>th</strong>e volume and le<strong>ac</strong>hate concentration in comparison<br />
wi<strong>th</strong> <strong>th</strong>e nitrification and denitrification processes for ammonia removal. It could also be<br />
said <strong>th</strong>at ammonia stripping is an appropriate option for pre-treatment <strong>of</strong> le<strong>ac</strong>hate even in<br />
terms <strong>of</strong> cost-effectiveness (Cheung, et al., 1997).<br />
In <strong>th</strong>e second stage <strong>of</strong> ammonia stripping studies as mentioned above, <strong>th</strong>e pilot-scale<br />
studies were done to confirm <strong>th</strong>e results obtained from laboratory-scale studies. The pilot<br />
scale study was conducted wi<strong>th</strong> le<strong>ac</strong>hate volume <strong>of</strong> 40 L at pH 11-12 and velocity gradient<br />
<strong>of</strong> 2,850 s -1 . The summary <strong>of</strong> <strong>th</strong>e pilot scale studies are given in Table F-5 <strong>of</strong> Appendix F.<br />
The cont<strong>ac</strong>t time was varied from 1 to 5 h. At e<strong>ac</strong>h hour, <strong>th</strong>e removal efficiency was<br />
measured. The average removal efficiency was found to be 89% at 5 h cont<strong>ac</strong>t time. From<br />
<strong>th</strong>e pilot scale studies, similar removal efficiency was expected at 4 h. Pilot scale results<br />
could be taken as a representative results as <strong>th</strong>e standard error decreased wi<strong>th</strong> increasing<br />
volume. When Yangin, et al. (2002) worked on ammonia stripping <strong>of</strong> domestic wastewater<br />
mixed wi<strong>th</strong> le<strong>ac</strong>hate, it was found <strong>th</strong>at 89% ammonia could be removed from <strong>th</strong>e UASBR<br />
effluent containing an ammonium concentration <strong>of</strong> 1,000-2,000 mg/L. So, wi<strong>th</strong> <strong>th</strong>e pilot<br />
scale study, we can be assured <strong>th</strong>at <strong>th</strong>e optimum condition persists at 5 h cont<strong>ac</strong>t time. To<br />
verify <strong>th</strong>is result again, wi<strong>th</strong> varying le<strong>ac</strong>hate ammonia concentration, <strong>th</strong>e experiment was<br />
conducted and <strong>th</strong>e average ammonia removal efficiency <strong>of</strong> 86% could be obtained wi<strong>th</strong><br />
standard deviation <strong>of</strong> 3 mg/L. The results <strong>of</strong> <strong>th</strong>is experiment are given in Table F-6 <strong>of</strong><br />
Appendix F.<br />
The mechanism in ammonia stripping could be due to <strong>th</strong>e ammonia desorption from<br />
<strong>th</strong>e surf<strong>ac</strong>e <strong>of</strong> <strong>th</strong>e liquid le<strong>ac</strong>hate into <strong>th</strong>e gaseous phase. It has also been said <strong>th</strong>at <strong>th</strong>e mass<br />
transfer <strong>of</strong> ammonia from liquid to air is proportional to <strong>th</strong>e concentration <strong>of</strong> ammoni<strong>ac</strong>al<br />
nitrogen in <strong>th</strong>e solution and is a first order re<strong>ac</strong>tion (Srina<strong>th</strong> and Loehr, 1974). However,<br />
<strong>th</strong>is could not be proved significantly in <strong>th</strong>e present study, as only a range <strong>of</strong> ammoni<strong>ac</strong>al<br />
nitrogen in <strong>th</strong>e le<strong>ac</strong>hate was used in <strong>th</strong>e experiment. Ano<strong>th</strong>er aspect to be discussed in <strong>th</strong>e<br />
study would be biological removal <strong>of</strong> ammonia in <strong>th</strong>e aeration process <strong>th</strong>rough agitation. It<br />
was clear <strong>th</strong>at <strong>th</strong>e ammonia was removed <strong>th</strong>rough stripping ra<strong>th</strong>er <strong>th</strong>an biological <strong>ac</strong>tivity<br />
as <strong>th</strong>ere wasn’t a significant increase in <strong>th</strong>e concentration <strong>of</strong> <strong>th</strong>e oxidized nitrogen<br />
94
concentration after treatment. O<strong>th</strong>er probable reasons could be absence <strong>of</strong> <strong>th</strong>e nitrification<br />
process at a pH as high as 11 which would ra<strong>th</strong>er inhibit <strong>th</strong>e process regardless <strong>of</strong> <strong>th</strong>e<br />
composition <strong>of</strong> le<strong>ac</strong>hate used, absence <strong>of</strong> sufficient nitrifying b<strong>ac</strong>terial population and<br />
oxidation <strong>of</strong> ammonia would require long generation time (Cheung, et al., 1997).<br />
4.4.2 Membrane Resistance and Membrane Cleaning<br />
The experiment on ammonia coupled membrane biore<strong>ac</strong>tor for le<strong>ac</strong>hate treatment<br />
was continued wi<strong>th</strong> <strong>th</strong>e membranes which were used for <strong>th</strong>e previous set <strong>of</strong> experiments. A<br />
new membrane was changed in bo<strong>th</strong> <strong>th</strong>e biore<strong>ac</strong>tors after few days <strong>of</strong> operation. The<br />
membrane was changed after 45 days in <strong>th</strong>e BMBR system and after 204 days in <strong>th</strong>e<br />
YMBR system. The data and figure for initial membrane resistance measurement are given<br />
in Table D-5 and Figure D-3 <strong>of</strong> Appendix D. The membrane resistance <strong>of</strong> <strong>th</strong>e new<br />
membrane used in <strong>th</strong>e BMBR system was found to be 7.07 x 10 11 m -1 and <strong>th</strong>at <strong>of</strong> YMBR<br />
was found to be 9.75 x 10 11 m -1 . The frequency <strong>of</strong> cleaning in <strong>th</strong>e BMBR system was twice,<br />
114 and 174 days after <strong>th</strong>e experiment started. It was found <strong>th</strong>at <strong>th</strong>e yeast system operated<br />
2.5 times more <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial system.<br />
Membrane fouling causing a decline <strong>of</strong> permeate flux can also be explained using <strong>th</strong>e<br />
resistance-in-series model, which provides a simplistic means to describe <strong>th</strong>e relationship<br />
between permeate flux and trans-membrane pressure. As described in <strong>th</strong>is model, <strong>th</strong>e<br />
permeate flux is given by <strong>th</strong>e Equation 4.2 and total resistance is given by Equation 4.3.<br />
Where;<br />
Rt = Rm + Rn + Rc Eq. 4.3<br />
Rm = intrinsic resistance (m -1 )<br />
Rn = irreversible fouling (m -1 )<br />
= resistance due to cake layer (m -1 )<br />
Rc<br />
This equation gives <strong>th</strong>e various parameters <strong>th</strong>at affect <strong>th</strong>e filtration performance.<br />
Irreversible fouling (Rn) results in supplementary resistance to filtration and is <strong>of</strong>ten due to<br />
adsorption <strong>of</strong> soluble organics. Resistance due to <strong>th</strong>e cake <strong>th</strong>at forms on <strong>th</strong>e membrane<br />
surf<strong>ac</strong>e (Rc) is a function <strong>of</strong> <strong>th</strong>e concentration and composition <strong>of</strong> suspended matters as<br />
well as <strong>th</strong>e applied hydraulic conditions.<br />
The total resistance (Rt) was measured immediately after <strong>th</strong>e clogging <strong>of</strong> <strong>th</strong>e<br />
membrane. Rm and Rn were obtained by measuring <strong>th</strong>e resistance <strong>of</strong> <strong>th</strong>e membrane after<br />
being washed wi<strong>th</strong> tap water to remove <strong>th</strong>e cake layer. The membrane resistance after<br />
chemical cleaning before <strong>th</strong>e operation was considered as Rm. Rc Value was derived from<br />
Rt, Rm, and Rn using Equation 4.3. To have a better understanding <strong>of</strong> <strong>th</strong>e membrane<br />
resistance and its role in bi<strong>of</strong>ouling, <strong>th</strong>e membrane resistance caused by <strong>th</strong>e varied f<strong>ac</strong>tors<br />
was measured while cleaning <strong>th</strong>e membrane in <strong>th</strong>e BMBR system. The varied resistance<br />
measured during <strong>th</strong>e first and <strong>th</strong>e second cleaning is presented in Table 4.13.<br />
95
Table 4.13 Determination <strong>of</strong> Membrane Resistance <strong>of</strong> Membrane Module after Clogging in<br />
BMBR system (A = 0.42 m 2 ; Pore Size = 0.1 µm)<br />
Membrane Resistance (m -1 Item<br />
)<br />
1 st Cleaning 2 nd Cleaning<br />
New membrane 7.07 x 10 11 7.07 x 10 11<br />
After long run (BMBR) 9.19 x 10 13 1.41 x 10 14<br />
After cleaning wi<strong>th</strong> tap water 1.97 x 10 13 2.43 x 10 13<br />
After chemical cleaning 8.71 x 10 11 9.79 x 10 11<br />
Total resistance (Rt) 9.19 x 10 13 1.41 x 10 14<br />
Initial membrane resistance for<br />
next run (Rm) 8.71 x 10 11 9.79 x 10 11<br />
Fouling resistance (Rn) 1.88 x 10 13 2.33 x 10 13<br />
Cake layer resistance (Rc) 7.22 x 10 13 1.17 x 10 14<br />
The total membrane resistance is a sum <strong>of</strong> cake layer resistance, intrinsic resistance<br />
and irreversible resistance due to fouling. The variation in transmembrane pressure wi<strong>th</strong><br />
time in <strong>th</strong>e MBR systems used for ammonia stripped le<strong>ac</strong>hate treatment is given in Figure<br />
4.23. The membrane resistance after <strong>th</strong>e long run was found to be 9.19 x 10 13 m -1 before<br />
<strong>th</strong>e first cleaning. Which fur<strong>th</strong>er increased to 1.41 x 10 14 m -1 before <strong>th</strong>e second cleaning<br />
was done. The cake layer contributed to 79% <strong>of</strong> <strong>th</strong>e total resistance during <strong>th</strong>e first<br />
cleaning which fur<strong>th</strong>er increased to 83% during <strong>th</strong>e second cleaning. From <strong>th</strong>e greatest<br />
contribution <strong>of</strong> cake resistance to <strong>th</strong>e total resistance, one could conclude <strong>th</strong>at <strong>th</strong>e<br />
formation <strong>of</strong> cake layer played a major role in flux decline during filtration (Kim, et al.,<br />
1998). This could be due to some loss due to <strong>th</strong>e irreversible resistance in <strong>th</strong>e membrane.<br />
Trans-membrane Pressure<br />
(kPa)<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
BMBR<br />
YMBR<br />
HRT<br />
0 50 100 150<br />
Time (day)<br />
200 250 300<br />
Figure 4.23 Trans-membrane Pressure Variation in MBR Process for Ammonia Stripped<br />
Le<strong>ac</strong>hate Treatment<br />
96<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
HRT (h)
After <strong>th</strong>e chemical cleaning <strong>of</strong> <strong>th</strong>e membrane during bo<strong>th</strong> <strong>th</strong>e times, 99% <strong>of</strong> <strong>th</strong>e<br />
initial membrane resistance could be obtained. The fouling resistance in <strong>th</strong>e membrane<br />
biore<strong>ac</strong>tor was 20% and 17% during <strong>th</strong>e first and second cleaning, respectively <strong>of</strong> <strong>th</strong>at <strong>of</strong><br />
<strong>th</strong>e total resistance. This indicated <strong>th</strong>at <strong>th</strong>e cake layer resistance was much higher <strong>th</strong>an <strong>th</strong>e<br />
fouling resistance in <strong>th</strong>e membranes. The reduction in flux due to membrane bi<strong>of</strong>ouling is<br />
largely affected by physico-chemical char<strong>ac</strong>teristics and physiology <strong>of</strong> <strong>ac</strong>tivated sludge as<br />
well as membrane materials (Kim, et al., 1998). The f<strong>ac</strong>tors affecting <strong>th</strong>e membrane<br />
fouling will be discussed in later part <strong>of</strong> <strong>th</strong>is chapter.<br />
4.4.3 Performance <strong>of</strong> Ammonia Stripping Coupled Membrane Biore<strong>ac</strong>tor Process<br />
As <strong>th</strong>e performance in terms <strong>of</strong> COD removal efficiency wi<strong>th</strong>out ammonia stripping<br />
was not significant wi<strong>th</strong> 16 and 24 h HRT, <strong>th</strong>e performance <strong>of</strong> MBR was evaluated in<br />
terms <strong>of</strong> bo<strong>th</strong> COD and BOD at HRT <strong>of</strong> 16 h followed by 24 h. Stable biomass retention in<br />
<strong>th</strong>e MBR is effective in BOD removal. The MBR system <strong>th</strong>ough effective in BOD removal,<br />
is not easy to remove nitrogen (Ahn, et al., 2002). The optimum conditions derived from<br />
ammonia stripping studies as described in section 4.4.1 were used for ammonia removal.<br />
Ammonia removal was used for nitrogen removal instead <strong>of</strong> nitrification-denitrification<br />
process because old le<strong>ac</strong>hate does not have sufficient degradable organics to supply <strong>th</strong>e<br />
b<strong>ac</strong>teria wi<strong>th</strong> carbon needed for grow<strong>th</strong>. The ammonia stripping was done once every <strong>th</strong>ree<br />
days to feed <strong>th</strong>e membrane biore<strong>ac</strong>tors. The performance could be evaluated as described<br />
below.<br />
(1) COD Removal Efficiency<br />
The COD <strong>of</strong> <strong>th</strong>e influent le<strong>ac</strong>hate ranged from 7,600 to 8,200 mg/L wi<strong>th</strong> 16 and 24 h<br />
HRT. After <strong>th</strong>e ammonia stripping, <strong>th</strong>e le<strong>ac</strong>hate was fed into <strong>th</strong>e feed tanks to feed<br />
membrane biore<strong>ac</strong>tors. In bo<strong>th</strong> <strong>th</strong>e operational conditions, wi<strong>th</strong> 16 and 24 h HRT, <strong>th</strong>e<br />
average MLSS concentration ranged from 11,000 to 12,000 mg/L. The MLSS<br />
concentration was similar to <strong>th</strong>e membrane biore<strong>ac</strong>tors wi<strong>th</strong>out ammonia stripping. The<br />
variation in <strong>th</strong>e MLSS concentration and <strong>th</strong>e influent COD influent wi<strong>th</strong> 16 and 24 h HRT<br />
is given in Figure 4.24 and 4.25, respectively. The advantages <strong>of</strong> biomass retention in<br />
membrane biore<strong>ac</strong>tor are <strong>th</strong>at, even <strong>th</strong>e slow growing organisms, normally washed <strong>of</strong>f in<br />
conventional process are retained in membrane biore<strong>ac</strong>tor (Ben Aim and Semmens, 2002).<br />
The entire range <strong>of</strong> data is given in Table G-1 to G-4 <strong>of</strong> Appendix G.<br />
The fluctuations in <strong>th</strong>e membrane biore<strong>ac</strong>tor treatment in terms <strong>of</strong> COD removal<br />
wi<strong>th</strong> ammonia stripping were found to be lower <strong>th</strong>an <strong>th</strong>at wi<strong>th</strong>out ammonia stripping. Bo<strong>th</strong><br />
YMBR and BMBR re<strong>ac</strong>tor wi<strong>th</strong>out ammonia stripping, did not show improvement in COD<br />
removal when <strong>th</strong>e HRT was increased, while in bo<strong>th</strong> <strong>th</strong>e systems <strong>th</strong>ere was slight<br />
improvement in COD removal when <strong>th</strong>e HRT was increased. The nitrogen removal in <strong>th</strong>e<br />
membrane biore<strong>ac</strong>tor was satisf<strong>ac</strong>tory. The probable reason for nitrogen removal would<br />
have been denitrification ra<strong>th</strong>er <strong>th</strong>an nitrification as <strong>th</strong>ere was not any sufficient increase in<br />
oxidized nitrogen compounds (Muller, et al., 1995). The COD removal in <strong>th</strong>e YMBR and<br />
BMBR wi<strong>th</strong> <strong>th</strong>e ammonia stripping was <strong>th</strong>e same. Bo<strong>th</strong> <strong>th</strong>e membrane re<strong>ac</strong>tors showed a<br />
COD removal <strong>of</strong> 72% at 16 h HRT and 76% at 24 h HRT. When Ahn, et al. (2002) treated<br />
le<strong>ac</strong>hate wi<strong>th</strong> 1,017 mg/L COD, <strong>th</strong>ey found <strong>th</strong>at <strong>th</strong>e MBR system could <strong>ac</strong>hieve a COD<br />
97
COD (mg/L)<br />
10000<br />
9000<br />
8000<br />
7000<br />
6000<br />
5000<br />
4000<br />
3000<br />
2000<br />
1000<br />
0<br />
MLSS (mg/L)<br />
16000<br />
14000<br />
12000<br />
10000<br />
8000<br />
6000<br />
4000<br />
2000<br />
0<br />
16 h HRT 24 h HRT<br />
0 50 100<br />
Time (Days)<br />
150 200<br />
Figure 4.24 Variation in COD at 16 and 24 h HRT<br />
16 h HRT 24 h HRT<br />
0 50 100<br />
Time (Days)<br />
150 200<br />
Figure 4.25 Variation in MLSS at 16 and 24 h HRT<br />
98
emoval <strong>of</strong> 38%. A higher removal in <strong>th</strong>e present study could be due to <strong>th</strong>e high<br />
concentration <strong>of</strong> biomass used. The COD removal at 16 and 24 h HRT wi<strong>th</strong> and wi<strong>th</strong>out<br />
ammonia stripping is presented in Figure 4.26.<br />
From Figure 4.26, it is clear <strong>th</strong>at <strong>th</strong>e ammonia stripping improved <strong>th</strong>e performance <strong>of</strong><br />
COD removal <strong>of</strong> <strong>th</strong>e BMBR much more <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e YMBR system as anticipated from<br />
<strong>th</strong>e toxicity studies.<br />
COD Removal<br />
(%)<br />
100<br />
95<br />
90<br />
85<br />
80<br />
75<br />
70<br />
65<br />
60<br />
55<br />
50<br />
Figure 4.26 COD Removal wi<strong>th</strong> and wi<strong>th</strong>out Ammonia Stripping at 16 and 24 h HRT<br />
Figure 4.27 shows <strong>th</strong>e expected improvement by ammonia stripping <strong>th</strong>rough<br />
biokinetic study and <strong>ac</strong>tual improvement for <strong>th</strong>e influent ammonium concentration.<br />
Though, <strong>th</strong>e expected improvement in terms <strong>of</strong> COD removal in <strong>th</strong>e yeast system was low,<br />
<strong>th</strong>e <strong>ac</strong>tual improvement was found to be much higher wi<strong>th</strong> 24 h HRT better <strong>th</strong>an <strong>th</strong>e 16 h<br />
HRT. The probable reason for <strong>th</strong>is could be <strong>th</strong>at <strong>th</strong>e biokinetic studies were done at a low<br />
substrate concentration as compared to <strong>th</strong>e <strong>ac</strong>tual simulated le<strong>ac</strong>hate. For <strong>th</strong>e BMBR<br />
system, <strong>th</strong>e improvements in <strong>th</strong>e COD removal for 24 h HRT was as anticipated <strong>th</strong>ough<br />
lower for 16 h HRT. This is ano<strong>th</strong>er indication to <strong>th</strong>e f<strong>ac</strong>t <strong>th</strong>at <strong>th</strong>e system was more<br />
stabilized at 24 h HRT <strong>th</strong>an at 16 h HRT. The standard deviation in <strong>th</strong>e COD removal at<br />
24 h HRT was 2 mg/L in <strong>th</strong>e BMBR system. Thus, suggesting <strong>th</strong>at in terms <strong>of</strong> COD<br />
removal was better at 24 h HRT.<br />
(2) BOD Removal Efficiency<br />
Wi<strong>th</strong>out Ammonia Stripping<br />
Wi<strong>th</strong> Ammonia Stripping<br />
BMBR-16h BMBR-24h YMBR-16h YMBR-24h<br />
As <strong>th</strong>e study wi<strong>th</strong>out ammonia stripping did not show a significant difference in <strong>th</strong>e<br />
COD removal, BOD was monitored in bo<strong>th</strong> <strong>th</strong>e effluents in addition to <strong>th</strong>e COD while<br />
working on ammonia stripped le<strong>ac</strong>hate. The BOD data for 16 and 24 h HRT is presented in<br />
Figure 4.28 and 4.29. The BOD removal in bo<strong>th</strong> <strong>th</strong>e BMBR and YMBR systems were<br />
above 94%. Ahn, et al. (2002) found <strong>th</strong>at a le<strong>ac</strong>hate wi<strong>th</strong> BOD around 250 to 300 mg/L,<br />
BOD removal was 97%. Though <strong>th</strong>e membrane biore<strong>ac</strong>tor was moderately efficient in <strong>th</strong>e<br />
removal <strong>of</strong> COD, <strong>th</strong>e BOD removal was high. This shows <strong>th</strong>at <strong>th</strong>e membrane biore<strong>ac</strong>tors<br />
are efficient in <strong>th</strong>e removal <strong>of</strong> <strong>th</strong>e degradable organics in <strong>th</strong>e le<strong>ac</strong>hate and <strong>th</strong>e probable<br />
99
eason for moderate removal efficiency could be because <strong>of</strong> <strong>th</strong>e refr<strong>ac</strong>tory nature <strong>of</strong> <strong>th</strong>e<br />
le<strong>ac</strong>hate.<br />
Improvement in COD<br />
Removal<br />
30%<br />
25%<br />
20%<br />
15%<br />
10%<br />
5%<br />
0%<br />
Biokinetic<br />
Study<br />
16h HRT<br />
Figure 4.27 Expected and Actual Improvement in COD Removal wi<strong>th</strong> Ammonia Stripping<br />
in <strong>th</strong>e YMBR and BMBR Systems<br />
The average BOD removal efficiency <strong>of</strong> <strong>th</strong>e 16 and 24 h HRT in bo<strong>th</strong> <strong>th</strong>e re<strong>ac</strong>tors is<br />
given in Figure 4.30. At 16 h HRT, BOD in <strong>th</strong>e b<strong>ac</strong>terial re<strong>ac</strong>tor was about 202 mg/L and<br />
<strong>th</strong>at <strong>of</strong> yeast re<strong>ac</strong>tor was 84 mg/L. At 24 h HRT, BOD <strong>of</strong> yeast effluent was wi<strong>th</strong>in <strong>th</strong>e<br />
wastewater discharge standards (30 mg/L) and b<strong>ac</strong>terial effluent slightly exceeded <strong>th</strong>e<br />
discharge standards (55 mg/L).<br />
As <strong>th</strong>e BOD removal was high, <strong>th</strong>e BOD/COD drastically reduced. The influent<br />
BOD/COD concentration was 0.4. As shown in Figure 4.31, <strong>th</strong>e BOD/COD ratio reduced<br />
significantly from 0.4 to 0.1 in <strong>th</strong>e BMBR and 0.01-0.03 in <strong>th</strong>e YMBR.<br />
The <strong>ac</strong>hieved low BOD/COD ratio indicated <strong>th</strong>at bo<strong>th</strong> YMBR and BMBR effluents<br />
contains a high refr<strong>ac</strong>tory organic substances which might be due to <strong>th</strong>e contribution <strong>of</strong> <strong>th</strong>e<br />
slowly biodegradable organics and non-biodegradable organics contained in <strong>th</strong>e raw<br />
le<strong>ac</strong>hate.<br />
100<br />
24h HRT<br />
BMBR<br />
YMBR
Influent BOD<br />
(mg/L)<br />
Influent BOD<br />
(mg/L)<br />
4500<br />
4000<br />
3500<br />
3000<br />
2500<br />
2000<br />
1500<br />
1000<br />
Figure 4.28 BOD in <strong>th</strong>e BMBR and YMBR Effluent at 16 h HRT<br />
4500<br />
4000<br />
3500<br />
3000<br />
2500<br />
2000<br />
1500<br />
1000<br />
0 10 20 30<br />
Time (Days)<br />
40 50 60<br />
Figure 4.29 BOD in <strong>th</strong>e BMBR and YMBR Effluent at 24 h HRT<br />
101<br />
Influent<br />
YMBR Effluent<br />
BMBR Effleunt<br />
0 20 40 60 80 100 120 140 160 180<br />
Time (Days)<br />
Influent<br />
YMBR Effluent<br />
BMBR Effleunt<br />
500<br />
400<br />
300<br />
200<br />
100<br />
0<br />
500<br />
400<br />
300<br />
200<br />
100<br />
0<br />
Effluent BOD<br />
(mg/L)<br />
Effluent BOD<br />
(mg/L)
BOD Removal Efficiency<br />
(%)<br />
100<br />
99<br />
98<br />
97<br />
96<br />
95<br />
94<br />
93<br />
92<br />
91<br />
90<br />
Figure 4.30 BOD Removal Efficiency in <strong>th</strong>e BMBR and YMBR Systems<br />
HRT<br />
24 h<br />
16 h<br />
BMBR-16h BMBR-24h YMBR-16h YMBR-24h<br />
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10<br />
BOD/COD<br />
Figure 4.31 BOD/COD <strong>of</strong> <strong>th</strong>e BMBR and YMBR Effluent<br />
102<br />
BMBR YMBR
(3) TKN Removal Efficiency<br />
The TKN Removal was high due to <strong>th</strong>e presence <strong>of</strong> ammonia stripping process. The<br />
TKN <strong>of</strong> <strong>th</strong>e influent was around 1,700 mg/L. The TKN <strong>of</strong> <strong>th</strong>e stripped le<strong>ac</strong>hate was found<br />
to be around 320-340 mg/L for 16 and 24 h HRT. The TKN <strong>of</strong> <strong>th</strong>e influent, stripped<br />
le<strong>ac</strong>hate and effluent along wi<strong>th</strong> effluent ammonical concentration for 16 and 24 h HRT in<br />
<strong>th</strong>e BMBR and YMBR systems is given in Figure 4.32 and 4.33, respectively.<br />
Concentration<br />
(mg/L)<br />
Concentration<br />
(mg/L)<br />
2100<br />
1800<br />
1500<br />
1200<br />
900<br />
600<br />
300<br />
0<br />
2400<br />
2100<br />
1800<br />
1500<br />
1200<br />
900<br />
600<br />
300<br />
0<br />
0 20 40 60 80 100 120 140 160<br />
Time (days)<br />
(a)<br />
0 5 10 15 20 25 30 35 40 45 50 55 60<br />
Time (days)<br />
TKN (Raw Le<strong>ac</strong>hate) TKN (Stripped Le<strong>ac</strong>hate)<br />
TKN (BMBR Effluent) NH4+-N (BMBR Effluent)<br />
(b)<br />
Figure 4.32 Influent and Effluent Nitrogen Content in BMBR at (a) 16 h HRT and<br />
(b) 24 h HRT<br />
103
The TKN removal in <strong>th</strong>e BMBR and <strong>th</strong>e YMBR re<strong>ac</strong>tor showed some difference<br />
wi<strong>th</strong> change in HRT. In <strong>th</strong>e BMBR system, <strong>th</strong>e effluent TKN and ammonical nitrogen<br />
concentration at 16 h HRT was 300 and 216 mg/L, while at 24 h HRT was 200 and 140<br />
mg/L, respectively. In <strong>th</strong>e YMBR system, <strong>th</strong>e effluent TKN and ammonical nitrogen<br />
concentration at 16 h HRT was 280 and 200 mg/L, while at 24 h HRT was 193 and 130<br />
mg/L, respectively. This showed <strong>th</strong>at <strong>th</strong>e 24 h HRT was more effective in TKN removal.<br />
Concentration<br />
(mg/L)<br />
Concentration<br />
(mg/L)<br />
2100<br />
1800<br />
1500<br />
1200<br />
900<br />
600<br />
300<br />
0<br />
2400<br />
2100<br />
1800<br />
1500<br />
1200<br />
900<br />
600<br />
300<br />
0<br />
0 20 40 60 80 100 120 140 160<br />
Time (days)<br />
(a)<br />
0 5 10 15 20 25 30 35 40 45 50 55 60<br />
Time (days)<br />
TKN (Raw Le<strong>ac</strong>hate) TKN (Stripped Le<strong>ac</strong>hate)<br />
TKN (YMBR Effluent) NH4+-N (YMBR Effluent)<br />
(b)<br />
Figure 4.33 Influent and Effluent Nitrogen Content in YMBR at (a) 16 h HRT and<br />
(b) 24 h HRT<br />
104
Figure 4.34 gives <strong>th</strong>e overall TKN removal wi<strong>th</strong> and wi<strong>th</strong>out ammonia stripping in<br />
<strong>th</strong>e BMBR and YMBR at 16 and 24 h HRT. The TKN removal was better in YMBR<br />
compared to <strong>th</strong>at <strong>of</strong> BMBR, <strong>th</strong>ough <strong>th</strong>e difference was found to be very less. The TKN<br />
removal in all conditions was found to be greater <strong>th</strong>an 80%.<br />
The TKN removal in <strong>th</strong>e ammonia stripped membrane biore<strong>ac</strong>tor took pl<strong>ac</strong>e at two<br />
stages. Though <strong>th</strong>e removal <strong>th</strong>rough ammonia stripping was predominantly by ammonia<br />
stripping process, some amount <strong>of</strong> TKN was removed in <strong>th</strong>e membrane biore<strong>ac</strong>tor. Figure<br />
4.35 gives <strong>th</strong>e difference between TKN removal wi<strong>th</strong> and wi<strong>th</strong>out ammonia stripping at 16<br />
and 24 h HRT in BMBR and YMBR systems.<br />
The 24 h HRT showed a better removal <strong>th</strong>an at 16 h HRT. The difference in TKN<br />
removal wi<strong>th</strong> and wi<strong>th</strong>out ammonia stripping in bo<strong>th</strong> <strong>th</strong>e MBR systems was found to be<br />
much greater in 24 h HRT <strong>th</strong>an in 16 h HRT.<br />
TKN Removal<br />
(%)<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
Wi<strong>th</strong>out Ammonia Stripping Wi<strong>th</strong> Ammonia Stripping<br />
BMBR-16h BMBR-24h YMBR-16h YMBR-24h<br />
Figure 4.34 Overall TKN Removal in BMBR and YMBR wi<strong>th</strong> and wi<strong>th</strong>out<br />
Ammonia Stripping<br />
105
TKN Removal<br />
(%)<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
4.5 O<strong>th</strong>er Studies<br />
Figure 4.35 TKN Removal in MBR Process at 16 and 24 h HRT<br />
4.5.1 Biodegradability <strong>of</strong> <strong>th</strong>e Le<strong>ac</strong>hate<br />
Wi<strong>th</strong>out Ammonia Stripping Wi<strong>th</strong> Ammonia Stripping<br />
BMBR-16h BMBR-24h YMBR-16h YMBR-24h<br />
Landfill le<strong>ac</strong>hates are usually compared to complex industrial wastewater streams<br />
which contain bo<strong>th</strong> toxic organic and inorganic contaminants (Krug and McDougall, 1988).<br />
Toxic and hazardous compounds can originate from landfill le<strong>ac</strong>hate as a result <strong>of</strong> soluble<br />
components <strong>of</strong> solid and liquid wastes being le<strong>ac</strong>hate into surf<strong>ac</strong>e and groundwater.<br />
The COD present in any wastewater can be categorized into two fr<strong>ac</strong>tions:<br />
biodegradable and non-biodegradable COD. The non-biodegradable COD has two subfr<strong>ac</strong>tions<br />
consisting <strong>of</strong> dissolved non-biodegradable organics and suspended nonbiodegradable<br />
organics. The same way, <strong>th</strong>e biodegradable COD has two fr<strong>ac</strong>tions<br />
comprising dissolved readily biodegradable organics (Ss) and suspended slowly<br />
biodegradable organics (Xs) (Ekama, et al., 1986; Vanrolleghem, et al., 1999).<br />
Respirometric me<strong>th</strong>od could be effective in measuring <strong>th</strong>e biodegradable component <strong>of</strong> <strong>th</strong>e<br />
landfill le<strong>ac</strong>hate. During <strong>th</strong>e feed period <strong>th</strong>e rate <strong>of</strong> supply <strong>of</strong> Ss is due to <strong>th</strong>at added via <strong>th</strong>e<br />
influent feed and <strong>th</strong>at realized to <strong>th</strong>e liquid via hydrolysis <strong>of</strong> Xs. After <strong>th</strong>e supply <strong>of</strong> Ss from<br />
<strong>th</strong>e feed ceases; OUR immediately drops to <strong>th</strong>e value, which is fixed by <strong>th</strong>e rate <strong>of</strong> Ss<br />
supply from <strong>th</strong>e hydrolysis <strong>of</strong> slowly degradable particular COD, Xs. In a batch test, an<br />
exponential decrease can be observed in respirogram after an initial peak formed due to <strong>th</strong>e<br />
presence <strong>of</strong> Ss in <strong>th</strong>e le<strong>ac</strong>hate. The concentration <strong>of</strong> Xs can also be assessed in a similar<br />
way (Kappeler and Gujer, 1992).<br />
To find out <strong>th</strong>e biodegradable component present in <strong>th</strong>e le<strong>ac</strong>hate, a le<strong>ac</strong>hate substrate<br />
concentration <strong>of</strong> 43.2 mg COD/L was injected into respirometer containing a sludge<br />
concentration <strong>of</strong> 924 mg VSS/L. OUR was measured at a temperature <strong>of</strong> 30 o C. The<br />
variation in OUR wi<strong>th</strong> time is shown in Figure 4.36. The readily biodegradable COD<br />
106
fr<strong>ac</strong>tion and slowly biodegradable COD fr<strong>ac</strong>tion in <strong>th</strong>e influent are related to <strong>th</strong>e oxygen<br />
utilization. The former is proportional to <strong>th</strong>e area between <strong>th</strong>e initial high OUR plot and<br />
horizontal line projected to <strong>th</strong>e vertical axis at <strong>th</strong>e level <strong>of</strong> <strong>th</strong>e second OUR plateau (Area I).<br />
The latter is proportional to <strong>th</strong>e area II. Area II includes <strong>th</strong>e utilization rate <strong>of</strong> endogenous<br />
sludge. The oxygen utilization in <strong>th</strong>e two phases is given as follows:<br />
Area I = OUR * Time * MLVSS * Volume <strong>of</strong> respirometer<br />
= 8.57 mg O2<br />
Area II = OUR * Time * MLVSS * Volume <strong>of</strong> respirometer<br />
= 12.89 mg O2<br />
OUR (mg/mg.h)<br />
0.014<br />
0.012<br />
0.010<br />
0.008<br />
0.006<br />
0.004<br />
0.002<br />
0.000<br />
Area I<br />
Area II<br />
0 100 200 300 400 500<br />
Time (min)<br />
Figure 4.36 Change <strong>of</strong> OUR at Different Time Period for Le<strong>ac</strong>hate Sample<br />
After obtaining <strong>th</strong>e oxygen consumption, <strong>th</strong>e yield coefficient was calculated by <strong>th</strong>e<br />
formulae,<br />
Yield coefficient (Y) = CODT – OC<br />
CODT<br />
= 38.88 – 21.46 = 0.45<br />
38.88<br />
Where,<br />
CODT = Total COD<br />
OC = Oxygen Consumption<br />
The readily biodegradable COD (Ss) and slowly biodegradable COD (Xs) can be<br />
calculated as follows:<br />
107
Where,<br />
Ss = Oxygen consumption for Ss * 100 Eq. 4.4<br />
(1-Y) * CODT<br />
Xs = Oxygen consumption for Xs * 100 Eq. 4.5<br />
(1-Y) * CODT<br />
Oxygen consumption for Ss = Area I<br />
Oxygen consumption for Xs = Area II<br />
Based on <strong>th</strong>e area covered by <strong>th</strong>e curve (area I), readily biodegradable COD, is equal<br />
to 40% <strong>of</strong> total area while area II, slowly biodegradable COD, is equal to 60% <strong>of</strong> total area.<br />
Thus, it could be said <strong>th</strong>at among <strong>th</strong>e biodegradation COD, readily degradable components<br />
are just 40% compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e slowly degradable component. This shows <strong>th</strong>e<br />
recalcitrant nature <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate and <strong>th</strong>e requirement <strong>of</strong> a long HRT for complete<br />
degradation <strong>of</strong> <strong>th</strong>e biodegradable components. Based on <strong>th</strong>e result, <strong>th</strong>e estimated readily<br />
biodegradable COD can be degraded wi<strong>th</strong>in 12 h.<br />
Though OUR experiments suggest <strong>th</strong>e readily biodegradable and slowly<br />
biodegradable components <strong>of</strong> <strong>th</strong>e biodegradable COD, it does not <strong>ac</strong>tually tell <strong>th</strong>e total<br />
biodegradable content present in <strong>th</strong>e le<strong>ac</strong>hate. To fur<strong>th</strong>er investigate on <strong>th</strong>is aspect, a 20<br />
days BOD was measured. It has suggested by Henze (1992) <strong>th</strong>at <strong>th</strong>e fr<strong>ac</strong>tions <strong>of</strong> organic<br />
matter in wastewater which are measured in terms <strong>of</strong> OUR and BOD5 are similar. Thus,<br />
<strong>th</strong>e relation between <strong>th</strong>e COD fr<strong>ac</strong>tion and BOD concentration may suggest <strong>th</strong>e<br />
biodegradability <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate.<br />
When <strong>th</strong>e 20 days BOD <strong>of</strong> <strong>th</strong>e raw le<strong>ac</strong>hate, stripped le<strong>ac</strong>hate, b<strong>ac</strong>terial and <strong>th</strong>e yeast<br />
effluent were measured, <strong>th</strong>e trend <strong>of</strong> increase in BOD was similar for raw and stripped<br />
le<strong>ac</strong>hate. The trend <strong>of</strong> increase in BOD for <strong>th</strong>e yeast and b<strong>ac</strong>terial effluent for <strong>th</strong>e first 10<br />
days was similar. The trend <strong>of</strong> <strong>th</strong>e 20 days BOD is given in Figure 4.37 and 4.38. The raw<br />
data is given in Table H-1 <strong>of</strong> Appendix H.<br />
After first 10 days, <strong>th</strong>e BOD <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial effluent did not vary significantly<br />
compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast effluent. Table 4.14 gives contribution <strong>of</strong> percent BOD <strong>of</strong> <strong>th</strong>e<br />
total BOD for le<strong>ac</strong>hate influent and effluent ay different time periods.<br />
Table 4.14 Contribution <strong>of</strong> BOD at 5, 10 and 15 Days to <strong>th</strong>e Total 20 Days BOD<br />
Percent BOD <strong>of</strong> 20 days BOD<br />
Day Raw Stripped YMBR BMBR<br />
Le<strong>ac</strong>hate Le<strong>ac</strong>hate Effluent Effluent<br />
BOD5 (mg/L) 67 47 25 38<br />
BOD10 (mg/L) 86 85 44 63<br />
BOD15 (mg/L) 94 100 81 75<br />
BOD20 (mg/L) 100 100 100 100<br />
108
BOD (mg/L)<br />
BOD (mg/L)<br />
6000<br />
5000<br />
4000<br />
3000<br />
2000<br />
1000<br />
Figure 4.37 20 Days BOD <strong>of</strong> <strong>th</strong>e Raw Le<strong>ac</strong>hate and Stripped Le<strong>ac</strong>hate<br />
100<br />
90<br />
80<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
0<br />
R 2 = 0.99<br />
Figure 4.38 20 Days BOD <strong>of</strong> <strong>th</strong>e YMBR and BMBR Effluents<br />
109<br />
R 2 = 0.98<br />
Raw Le<strong>ac</strong>hate<br />
Stripped Le<strong>ac</strong>hate<br />
0 5 10 15 20 25<br />
Time (Days)<br />
R 2 = 0.98<br />
R 2 = 0.96<br />
YMBR Effluent<br />
BMBR Effluent<br />
0 5 10 15 20 25<br />
Time (Days)
From <strong>th</strong>e data obtained above, it can be seen <strong>th</strong>at 5 days BOD contributes to about<br />
67% <strong>of</strong> <strong>th</strong>e 20 days COD present in <strong>th</strong>e raw le<strong>ac</strong>hate, while in <strong>th</strong>e BMBR and YMBR<br />
effluent; <strong>th</strong>e 5 days BOD contributed only 38 and 25% <strong>of</strong> <strong>th</strong>e 20 days BOD. This shows<br />
<strong>th</strong>at compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e raw le<strong>ac</strong>hate, <strong>th</strong>e effluents <strong>of</strong> <strong>th</strong>e membrane biore<strong>ac</strong>tors take a<br />
longer time to degrade <strong>th</strong>e organics suggesting <strong>th</strong>e presence <strong>of</strong> greater amount <strong>of</strong> slowly<br />
biodegradable organics. In comparison between YMBR and BMBR effluents, slowly<br />
biodegradable organics in YMBR effluent was higher <strong>th</strong>an <strong>th</strong>at in BMBR effluent.<br />
When <strong>th</strong>e BOD/COD ratio for raw le<strong>ac</strong>hate was considered, it was found <strong>th</strong>at<br />
BOD5/COD was 0.45 which increased to a BOD20/COD <strong>of</strong> 0.68 after 20 days. This<br />
suggests <strong>th</strong>at <strong>th</strong>e degradable component in <strong>th</strong>e raw le<strong>ac</strong>hate is almost 68%. The<br />
BOD5/COD <strong>of</strong> bo<strong>th</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast effluent was found to be 0.01. Though, <strong>th</strong>e<br />
b<strong>ac</strong>terial and yeast effluent had a similar BOD5/COD ratio, <strong>th</strong>e BOD20/COD ratio <strong>of</strong> <strong>th</strong>e<br />
b<strong>ac</strong>terial and yeast effluent varied wi<strong>th</strong> a ratio <strong>of</strong> 0.02 and 0.04, respectively. This also<br />
suggests <strong>th</strong>at <strong>th</strong>e slowly degradable components are more in <strong>th</strong>e yeast effluent in<br />
comparison wi<strong>th</strong> b<strong>ac</strong>terial effluent.<br />
4.5.2 Molecular Weight Cut-<strong>of</strong>f<br />
The organic matter present in <strong>th</strong>e le<strong>ac</strong>hate varies and is dependent on <strong>th</strong>e waste<br />
composition and degree <strong>of</strong> degradation. The medium molecular weight compounds wi<strong>th</strong><br />
molecular weight (MW) between 500 and 10,000 Da are dominated by carboxylic and<br />
hydroxylic groups wi<strong>th</strong> fulvic <strong>ac</strong>id and humic fr<strong>ac</strong>tion also contributing to <strong>th</strong>is fr<strong>ac</strong>tion in<br />
<strong>th</strong>e le<strong>ac</strong>hate (Chian and DeWalle, 1976; Harmsen, 1983). They are difficult to degrade and<br />
are termed refr<strong>ac</strong>tory. The fulvic and humic-like compounds present in le<strong>ac</strong>hate are formed<br />
from micobiological processes from <strong>th</strong>e intermediate products <strong>of</strong> degradation <strong>of</strong> polymeric<br />
organic compounds such as lignine (Andreux, 1979).<br />
The high molecular weight organics are usually stable to degradation. The<br />
effectiveness <strong>of</strong> a treatment process can be related to <strong>th</strong>e removal <strong>of</strong> specific organic<br />
fr<strong>ac</strong>tion in le<strong>ac</strong>hate. Bo<strong>th</strong> fulvic and humic substances are inert to biological treatment.<br />
Therefore, fr<strong>ac</strong>tionating <strong>th</strong>e COD based on molecular weight can <strong>ac</strong>t as an indicator to <strong>th</strong>e<br />
removal efficiency and degradation potential <strong>of</strong> <strong>th</strong>e biological system.<br />
According to <strong>th</strong>e results, <strong>th</strong>e molecular weight distribution or molecular weight cut<strong>of</strong>f<br />
(MWCO) was computed by measuring <strong>th</strong>e COD concentration <strong>of</strong> e<strong>ac</strong>h fr<strong>ac</strong>tion and <strong>th</strong>e<br />
volume filtered. The transformation <strong>of</strong> organic substances corresponding to <strong>th</strong>e change <strong>of</strong><br />
COD mass is shown in Figure 4.39. Detailed calculation is given in Table H-3 <strong>of</strong> Appendix<br />
H.<br />
As shown in <strong>th</strong>e figure, <strong>th</strong>e raw le<strong>ac</strong>hate contained a higher fr<strong>ac</strong>tion <strong>of</strong> high<br />
molecular weight compounds (> 50 k). The low-molecular weight fr<strong>ac</strong>tions, which include<br />
lower molecular weight compounds, were present at low fr<strong>ac</strong>tion. Figure 4.40 shows<br />
percent COD contribution <strong>of</strong> various molecular weight components to <strong>th</strong>e total COD in<br />
raw le<strong>ac</strong>hate, stripped le<strong>ac</strong>hate, b<strong>ac</strong>terial and yeast effluents.<br />
110
Figure 4.39 Molecular Weight Cut-<strong>of</strong>f <strong>of</strong> Raw Le<strong>ac</strong>hate, Stripped Le<strong>ac</strong>hate, B<strong>ac</strong>terial<br />
and Yeast Effluents<br />
COD<br />
COD (mg/L)<br />
8000<br />
7000<br />
6000<br />
5000<br />
4000<br />
3000<br />
2000<br />
1000<br />
0<br />
Raw<br />
Le<strong>ac</strong>hate<br />
Stripped<br />
Le<strong>ac</strong>hate<br />
Figure 4.40 Percent Contribution <strong>of</strong> Various Molecular Weight Compounds to <strong>th</strong>e<br />
Total<br />
The compounds greater <strong>th</strong>an 50 k molecular weight contributed almost 80% <strong>of</strong> <strong>th</strong>e<br />
raw le<strong>ac</strong>hate COD. It could be found <strong>th</strong>at some portion <strong>of</strong> <strong>th</strong>e > 50 k compounds is broken<br />
down into < 5 k after ammonia stripping. This is indicated by <strong>th</strong>e increase <strong>of</strong> < 5 k<br />
compounds. The > 5 k fr<strong>ac</strong>tion in <strong>th</strong>e raw le<strong>ac</strong>hate after stripping increased from 0 to 17%,<br />
while <strong>th</strong>e > 50 k fr<strong>ac</strong>tion reduced from 87 to 65%. The 10-50 k and 5-10 k fr<strong>ac</strong>tion did not<br />
increase significantly. The increase in 10-50 k and 5-10 k fr<strong>ac</strong>tions was from 5 to 6% and 8<br />
to 11%, respectively. Yoon, et al. (1998) showed <strong>th</strong>at about 72-89% <strong>of</strong> <strong>th</strong>e organics greater<br />
<strong>th</strong>an MW 500 could be removed and 42% <strong>of</strong> <strong>th</strong>e organics wi<strong>th</strong> less <strong>th</strong>an MW 500 could be<br />
removed from <strong>th</strong>e le<strong>ac</strong>hate using Fenton’s process. However, it was noticed <strong>th</strong>at Fenton’s<br />
process was not effective in removing organics less <strong>th</strong>an MW <strong>of</strong> 500.<br />
The MWCO after MBR treatment indicated notable reduction in > 50 k fr<strong>ac</strong>tion. The<br />
> 50 k fr<strong>ac</strong>tion reduced to 3% in <strong>th</strong>e yeast effluent and 7% in <strong>th</strong>e b<strong>ac</strong>terial system. The<br />
lower molecular weight compounds wi<strong>th</strong> MW 10-50 k, 5-10 k and >5 k in <strong>th</strong>e yeast<br />
effluent increased by 3 to 9%, 7 to 19% and 18 to 65%, respectively. These fr<strong>ac</strong>tions<br />
increased from 6 to 12%, 11 to 31% and 18 to 69%, respectively in <strong>th</strong>e b<strong>ac</strong>terial system.<br />
Using <strong>th</strong>e aerated lagoon for <strong>th</strong>e treatment <strong>of</strong> le<strong>ac</strong>hate, it was found <strong>th</strong>at only 19-28% <strong>of</strong><br />
<strong>th</strong>e total le<strong>ac</strong>hate organics was composed <strong>of</strong> organics less <strong>th</strong>an MW 500 in <strong>th</strong>e effluent<br />
111<br />
Yeast<br />
Effleunt<br />
B<strong>ac</strong>terial<br />
Effluent<br />
MW>50k MW 10k-50k MW 5k-10k MW
(Yoon, et al., 1998). This shows <strong>th</strong>at <strong>th</strong>e complex higher molecular weight compounds<br />
could be degraded effectively using membrane biore<strong>ac</strong>tor systems. For <strong>th</strong>e yeast and<br />
b<strong>ac</strong>teria effluent, <strong>th</strong>e increase <strong>of</strong> <strong>th</strong>e COD <strong>of</strong> below 5 k MW fr<strong>ac</strong>tion could be explained by<br />
<strong>th</strong>e biodegradation <strong>of</strong> high molecular weight organic substances to compounds below 5 k<br />
MW, as confirmed by <strong>th</strong>e decrease <strong>of</strong> <strong>th</strong>e COD <strong>of</strong> <strong>th</strong>e 5 k MW UF retentate. Similar<br />
results were obtained while treating le<strong>ac</strong>hate in aerobic and anaerobic system by Gourdon,<br />
et al. (1989). The studies also revealed <strong>th</strong>at recalcitrant organics were non-degradable in<br />
anaerobiosis, while it could be degraded to 50% in aerobic conditions.<br />
The COD removal after <strong>th</strong>e membrane biore<strong>ac</strong>tor treatment was from 7,500 mg/L to<br />
about 1,950 mg/L in bo<strong>th</strong> <strong>th</strong>e re<strong>ac</strong>tors. Among <strong>th</strong>e COD <strong>of</strong> 7,500 mg/L, about 5,500 mg/L<br />
was removed by <strong>th</strong>e membrane biore<strong>ac</strong>tor system, ei<strong>th</strong>er <strong>th</strong>rough degradation for energy<br />
consumption or <strong>th</strong>rough assimilation.<br />
To fur<strong>th</strong>er understand <strong>th</strong>e degradable components present in <strong>th</strong>e le<strong>ac</strong>hate and <strong>th</strong>eir<br />
molecular weight distribution, ano<strong>th</strong>er sample was analyzed wi<strong>th</strong> BOD along wi<strong>th</strong> COD<br />
after fr<strong>ac</strong>tionation. Figure 4.41 and 4.42 gives <strong>th</strong>e COD and BOD contribution <strong>of</strong><br />
compounds at different molecular weight. Table H-4 <strong>of</strong> Appendix H gives <strong>th</strong>e detailed<br />
calculation <strong>of</strong> <strong>th</strong>e results. In <strong>th</strong>e second sample showed a slight difference from <strong>th</strong>e first<br />
sample. The > 50 k fr<strong>ac</strong>tion decreased from 91% to 72% and corresponding increase <strong>of</strong> <strong>th</strong>e<br />
< 5 k from 0 to 18%.<br />
When <strong>th</strong>e analysis <strong>of</strong> <strong>th</strong>e molecular weight fr<strong>ac</strong>tions having organic matter below<br />
MW 500 <strong>of</strong> <strong>th</strong>e le<strong>ac</strong>hate was done, it has been shown <strong>th</strong>at <strong>th</strong>ey contain syn<strong>th</strong>etic organics<br />
and solvents such as aromatic and alcoholic groups. Phenols, amines and chlorinated<br />
organics were also found in <strong>th</strong>is fr<strong>ac</strong>tion. As suggested earlier, <strong>th</strong>e fr<strong>ac</strong>tions in 5 k to 10 k<br />
and higher molecular weight contained humic and fulvic substances, along wi<strong>th</strong> products<br />
<strong>of</strong> municipal dumping and natural fermentation (Slater, et al., 1985). In ano<strong>th</strong>er study on<br />
le<strong>ac</strong>hate sample suggested <strong>th</strong>at relatively high concentrations <strong>of</strong> carbohydrates could be<br />
observed in a high molecular weight fr<strong>ac</strong>tions and substantial quantities <strong>of</strong> aromatic<br />
hydroxyl and carboxylic compounds present in <strong>th</strong>e lower molecular weight fr<strong>ac</strong>tion (Chian,<br />
1977).<br />
112
COD (mg/L)<br />
8000<br />
6000<br />
4000<br />
2000<br />
COD (%)<br />
0<br />
Raw<br />
Le<strong>ac</strong>hate<br />
Stripped<br />
Le<strong>ac</strong>hate<br />
Figure 4.41 Molecular Weight Cut-<strong>of</strong>f <strong>of</strong> Le<strong>ac</strong>hate (a) COD (mg/L) (b) COD (%)<br />
113<br />
Yeast<br />
Effleunt<br />
B<strong>ac</strong>terial<br />
Effluent<br />
MW>50k MW 10k-50k MW 5k-10k MW50k MW 10k-50k<br />
MW 5k-10k MW
BOD (mg/L)<br />
4000<br />
3000<br />
2000<br />
1000<br />
0<br />
Raw<br />
Le<strong>ac</strong>hate<br />
Stripped<br />
Le<strong>ac</strong>hate<br />
Figure 4.42 Molecular Weight Cut-<strong>of</strong>f <strong>of</strong> Le<strong>ac</strong>hate (a) BOD (mg/L) (b) BOD (%)<br />
While analyzing <strong>th</strong>e BOD content <strong>of</strong> <strong>th</strong>e fr<strong>ac</strong>tions, it was found <strong>th</strong>at 88% (BOD) <strong>of</strong><br />
91% (COD) <strong>of</strong> <strong>th</strong>e > 50 k fr<strong>ac</strong>tion was biodegradable. As <strong>th</strong>is could be confirmed by <strong>th</strong>e<br />
3% remaining > 50 k COD content in <strong>th</strong>e b<strong>ac</strong>terial effluent after membrane biore<strong>ac</strong>tor<br />
treatment. Looking at <strong>th</strong>e BOD content in <strong>th</strong>e effluent, it was found <strong>th</strong>at in <strong>th</strong>e yeast as well<br />
as <strong>th</strong>e b<strong>ac</strong>terial effluent < 5 k molecular weight components contributed to <strong>th</strong>e maximum<br />
BOD when compared to <strong>th</strong>e o<strong>th</strong>er fr<strong>ac</strong>tions. The COD content also showed a similar trend.<br />
114<br />
Yeast<br />
Effleunt<br />
B<strong>ac</strong>terial<br />
Effluent<br />
MW>50k MW 10k-50k MW 5k-10k MW50k MW 10k-50k MW 5k-10k MW
Though, <strong>th</strong>e obtained COD removal efficiency <strong>of</strong> bo<strong>th</strong> systems was slightly different,<br />
<strong>th</strong>e majority <strong>of</strong> organic concentrations in bo<strong>th</strong> effluents were in <strong>th</strong>e lower molecular weight<br />
range indicating <strong>th</strong>at yeast and b<strong>ac</strong>teria were effective in degrading high molecular weight<br />
organics. The high molecular weight organics may be highly refr<strong>ac</strong>tory organics (Hosomi,<br />
et al., 1989). However, <strong>th</strong>e effluent from bo<strong>th</strong> systems still consists <strong>of</strong> <strong>th</strong>e medium<br />
molecular weight organics such as fulvic <strong>ac</strong>id which are unaffected by biological<br />
treatment. It could be fur<strong>th</strong>er treated wi<strong>th</strong> post treatment such as ozonation, increasing <strong>th</strong>e<br />
biodegradable organics or even elevating <strong>th</strong>e water quality <strong>of</strong> <strong>th</strong>e final effluent.<br />
4.5.3 Sludge Properties<br />
In <strong>th</strong>e membrane coupled biological treatment systems, complete separation <strong>of</strong><br />
microorganisms is possible; <strong>th</strong>us, high microbial concentration as well as excellent effluent<br />
quality (Kim, et al., 1998) can be <strong>ac</strong>hieved. The membrane bi<strong>of</strong>ouling could be largely<br />
affected by physico-chemical char<strong>ac</strong>teristics and <strong>th</strong>e physiology <strong>of</strong> <strong>th</strong>e <strong>ac</strong>tivated sludge as<br />
well as <strong>th</strong>e membrane materials (Sato and Ishii, 1991; Pouet and Grasmick, 1995; Chang,<br />
et al., 1996) Therefore, <strong>th</strong>e sludge properties <strong>of</strong> <strong>th</strong>e membrane biore<strong>ac</strong>tors are important in<br />
terms <strong>of</strong> membrane fouling and sludge dewaterability. Dewaterability is usually measured<br />
in terms <strong>of</strong> Capillary Suction Time (CST) for evaluating <strong>th</strong>e performance <strong>of</strong> sludge<br />
dewatering. Sludge Volume Index (SVI) is ano<strong>th</strong>er indicator used to measure <strong>th</strong>e<br />
settleability <strong>of</strong> <strong>th</strong>e sludge. The b<strong>ac</strong>terial sludge showed a better dewatering quality<br />
compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast system as shown in Table 4.15. As suspended solids also<br />
affect <strong>th</strong>e sludge properties, <strong>th</strong>e MLSS was also measured. Higher viscosity and<br />
dewaterability could be attributed to <strong>th</strong>e difference between MLSS <strong>of</strong> mixed b<strong>ac</strong>teria<br />
sludge and mixed yeast sludge. But, <strong>th</strong>e difference in <strong>th</strong>e MLSS was not found to be large.<br />
Table 4.15 Sludge Properties in <strong>th</strong>e YMBR and BMBR Systems<br />
Sample Re<strong>ac</strong>tor DSVI (ml/gSS) Viscosity (cP) CST (s/g SS) SS (mg/L)<br />
1<br />
YMBR<br />
BMBR<br />
not settle<br />
not settle<br />
6.24<br />
13.00<br />
-<br />
-<br />
-<br />
-<br />
2<br />
YMBR<br />
BMBR<br />
not settle<br />
79<br />
6.30<br />
9.78<br />
128<br />
12<br />
13,267<br />
14,133<br />
3<br />
YMBR<br />
BMBR<br />
not settle<br />
60<br />
-<br />
-<br />
126<br />
10<br />
13,367<br />
13,233<br />
Though <strong>th</strong>e b<strong>ac</strong>terial sludge showed a better dewaterability, <strong>th</strong>e viscosity <strong>of</strong> <strong>th</strong>e<br />
b<strong>ac</strong>terial system was found to be more <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast system. The content <strong>of</strong> micr<strong>of</strong>loc<br />
components, such as EPS might have an influence on <strong>th</strong>e permeability (Kim, et al.,<br />
1998). This could be one <strong>of</strong> <strong>th</strong>e reasons for a frequent membrane fouling in <strong>th</strong>e b<strong>ac</strong>terial<br />
system compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast system. Along wi<strong>th</strong> <strong>th</strong>e MLSS, MLVSS <strong>of</strong> <strong>th</strong>e sludge<br />
was also measured as given in Table 4.16.<br />
When MLVSS/MLSS was measured, it was found <strong>th</strong>at <strong>th</strong>e b<strong>ac</strong>terial sludge had a<br />
lower degradability (0.6) compared to <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast sludge (0.7). However, <strong>th</strong>e<br />
difference between <strong>th</strong>e degradability <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial sludge and yeast sludge was not much.<br />
115
Table 4.16 MLSS and MLVSS Concentrations in Yeast and B<strong>ac</strong>teria Re<strong>ac</strong>tors<br />
Sample Re<strong>ac</strong>tor MLSS (mg/L) MLVSS (mg/L) MLVSS/MLSS<br />
1<br />
YMBR<br />
BMBR<br />
12,750<br />
12,867<br />
9,866<br />
8,467<br />
0.77<br />
0.66<br />
2<br />
YMBR<br />
BMBR<br />
13,267<br />
14,133<br />
9,834<br />
9,066<br />
0.74<br />
0.64<br />
3<br />
YMBR<br />
BMBR<br />
12,433<br />
12,167<br />
9,667<br />
8,167<br />
0.78<br />
0.67<br />
4<br />
YMBR<br />
BMBR<br />
13,367<br />
13,233<br />
9,833<br />
8,333<br />
0.74<br />
0.63<br />
4.5.4 EPS Formation<br />
The sludge surf<strong>ac</strong>e is polymeric in nature comprising <strong>of</strong> protein, polys<strong>ac</strong>charides,<br />
nucleic <strong>ac</strong>id and lipid (Goodwin and Foster, 1985). These extr<strong>ac</strong>ellular polymeric<br />
substances excreted by <strong>th</strong>e microorganisms in <strong>th</strong>e microbial floc are a major foulant in <strong>th</strong>e<br />
membrane coupled <strong>ac</strong>tivated sludge process (Chang, et al., 1996; Nagaoka, et al., 1996).<br />
So, in addition to <strong>th</strong>e sludge properties, EPS <strong>of</strong> <strong>th</strong>e mixed liquor <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast<br />
system was measured. Table 4.17 and 4.18 summarizes <strong>th</strong>e variation in bound and soluble<br />
EPS <strong>of</strong> YMBR and BMBR. The EPS components could be sub-divided into two parts;<br />
namely <strong>th</strong>e bound and soluble EPS. The bound EPS corresponds to <strong>th</strong>e polymeric<br />
substances adhered toge<strong>th</strong>er wi<strong>th</strong> e<strong>ac</strong>h o<strong>th</strong>er and to <strong>th</strong>e microorganisms. The soluble EPS<br />
indicates <strong>th</strong>e microbial products which have been produced by <strong>th</strong>e microorganisms and<br />
suspended in <strong>th</strong>e mixed liquor in a soluble form. Bo<strong>th</strong> <strong>th</strong>e bound and soluble EPS were<br />
measured as TOC.<br />
Table 4.17 Bound EPS Concentration in <strong>th</strong>e YMBR and BMBR Systems<br />
Sample Re<strong>ac</strong>tor MLSS<br />
(mg/L)<br />
TOC<br />
(mg/g SS)<br />
Protein<br />
(mg/g SS)<br />
Carbohydrate<br />
(mg/g SS)<br />
Protein/Carbohydrate<br />
1 YMBR 12,750 46.7 35.4 24.1 1.47<br />
BMBR 12,867 47.3 35.5 26.2 1.35<br />
2 YMBR 13,267 43.5 34.5 21.0 1.64<br />
BMBR 14,133 42.3 30.6 25.0 1.23<br />
Table 4.18 Soluble EPS Concentration in <strong>th</strong>e YMBR and BMBR Systems<br />
Sample Re<strong>ac</strong>tor MLSS<br />
(mg/L)<br />
TOC<br />
(mg/g SS)<br />
Protein<br />
(mg/g SS)<br />
Carbohydrate<br />
(mg/g SS)<br />
Protein/Carbohydrate<br />
1 YMBR 12,750 133.1 53.4 41.2 1.29<br />
BMBR 12,867 138.3 74.8 44.9 1.66<br />
2 YMBR 13,267 123.2 50.3 46.9 1.07<br />
BMBR 14,133 147.9 72.1 46.4 1.55<br />
While measuring <strong>th</strong>e bound and soluble EPS <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast system, it was<br />
found <strong>th</strong>at in comparison between YMBR and BMBR, bound EPS concentration in terms<br />
<strong>of</strong> TOC was not different while, soluble EPS <strong>of</strong> mixed b<strong>ac</strong>terial sludge was higher <strong>th</strong>an<br />
<strong>th</strong>at <strong>of</strong> mixed yeast sludge. Thus, <strong>th</strong>is indicates soluble EPS could be <strong>th</strong>e f<strong>ac</strong>tor affecting<br />
<strong>th</strong>e membrane bi<strong>of</strong>ouling. In <strong>th</strong>e soluble EPS, <strong>th</strong>e protein content was also less. A yeast<br />
116
cake used on <strong>th</strong>e top <strong>of</strong> <strong>th</strong>e membrane usually <strong>ac</strong>ts as a secondary membrane which retains<br />
protein aggregates, reducing protein fouling <strong>of</strong> <strong>th</strong>e primary membrane (Guell, et al., 1999).<br />
These could be <strong>th</strong>e reasons for lower membrane fouling in <strong>th</strong>e yeast membrane.<br />
The protein and carbohydrates form <strong>th</strong>e main component <strong>of</strong> <strong>th</strong>e EPS; because <strong>of</strong><br />
<strong>th</strong>ese <strong>th</strong>e EPS components were also measured. It is also interesting to note <strong>th</strong>at <strong>th</strong>e protein<br />
to carbohydrate ratio in <strong>th</strong>e bound EPS was higher in yeast re<strong>ac</strong>tor <strong>th</strong>an <strong>th</strong>e b<strong>ac</strong>terial<br />
re<strong>ac</strong>tor and <strong>th</strong>e protein to carbohydrate ratio in <strong>th</strong>e soluble EPS was higher in <strong>th</strong>e b<strong>ac</strong>terial<br />
re<strong>ac</strong>tor <strong>th</strong>an <strong>th</strong>e yeast re<strong>ac</strong>tor. This may suggest <strong>th</strong>at higher protein to carbohydrate ratio<br />
plays a more important role in membrane fouling, if present in <strong>th</strong>e soluble EPS ra<strong>th</strong>er <strong>th</strong>an<br />
<strong>th</strong>at <strong>of</strong> <strong>th</strong>e bound EPS.<br />
4.5.5 Conductivity and TDS<br />
As <strong>th</strong>e TDS and conductivity are also important parameters for determining le<strong>ac</strong>hate<br />
quality, <strong>th</strong>e TDS and conductivity was monitored for a short period. The average<br />
conductivity and TDS <strong>of</strong> raw le<strong>ac</strong>hate were found to be 29,213 µS/cm and 14,603 mg/L,<br />
respectively. After stripping, <strong>th</strong>e le<strong>ac</strong>hate contained an average conductivity <strong>of</strong> 42,255<br />
µS/cm and average TDS <strong>of</strong> 21,128 mg/L. For YMBR and BMBR systems, <strong>th</strong>e<br />
conductivity and TDS concentration were not different (Table 4.19). The TDS and <strong>th</strong>e<br />
conductivity exceeded <strong>th</strong>e effluent discharge standards.<br />
Table 4.19 Conductivity and TDS Concentrations in Le<strong>ac</strong>hate and Effluents<br />
Conductivity (µS/cm)<br />
Sample Raw Stripped YMBR BMBR YMBR BMBR<br />
Le<strong>ac</strong>hate Le<strong>ac</strong>hate Effluent Effluent Re<strong>ac</strong>tor Re<strong>ac</strong>tor<br />
1 30,060 43,140 40,980 40,830 36,690 37,530<br />
2 29,640 42,360 36,090 35,760 36,990 38,130<br />
3 29,040 41,310 38,940 41,400 37,650 39,180<br />
4 28,110 42,210 36,930 36,600 35,940 35,010<br />
Average 29,213 42,255 38,235 38,648 36,818 37,463<br />
TDS (mg/L)<br />
Sample Raw Stripped YMBR BMBR YMBR BMBR<br />
Le<strong>ac</strong>hate Le<strong>ac</strong>hate Effluent Effluent Re<strong>ac</strong>tor Re<strong>ac</strong>tor<br />
1 15,030 21,570 20,490 20,400 18,360 18,750<br />
2 14,820 21,180 18,060 17,880 18,480 19,050<br />
3 14,520 20,640 19,470 20,670 18,840 19,590<br />
4 14,040 21,120 18,450 18,300 17,970 17,520<br />
Average 14,603 21,128 19,118 19,313 18,413 18,728<br />
4.5.6 Cost Analysis for Operation<br />
To fur<strong>th</strong>er compare <strong>th</strong>e overall performance <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial and yeast membrane<br />
biore<strong>ac</strong>tor, <strong>th</strong>e cost analysis <strong>of</strong> <strong>th</strong>e two systems was done. Table 4.20 gives <strong>th</strong>e cost <strong>of</strong><br />
chemicals used for pH adjustment. Table 4.21 gives <strong>th</strong>e overall treatment cost for e<strong>ac</strong>h<br />
117
treatment cost. Chemical cost required for MBR operation wi<strong>th</strong> and wi<strong>th</strong>out ammonia<br />
stripping is given in Table H-5 and H-6 <strong>of</strong> Appendix H.<br />
Table 4.20 Cost <strong>of</strong> Chemical Used for pH Adjustment<br />
Item Equipments and Chemicals Quantity<br />
Cost<br />
(unit)<br />
(Baht)<br />
1 NaOH (commercial grade) 25 kg/pk 750<br />
2 H2SO4 (commercial grade) 30 L/container 420<br />
While comparing <strong>th</strong>e chemical cost required for <strong>th</strong>e b<strong>ac</strong>terial and yeast membrane<br />
biore<strong>ac</strong>tor, it was found <strong>th</strong>at <strong>th</strong>e cost required for le<strong>ac</strong>hate treatment using <strong>th</strong>e b<strong>ac</strong>terial<br />
system is lower <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast system, <strong>th</strong>ough <strong>th</strong>e difference between <strong>th</strong>e two<br />
systems was not much.<br />
Table 4.21 Total Chemical Cost Requirement for E<strong>ac</strong>h Treatment System<br />
Treatment System Chemical Cost (Baht/m 3 )<br />
YMBR 93<br />
BMBR 5<br />
Coupling ammonia stripping wi<strong>th</strong> YMBR 662<br />
Coupling ammonia stripping wi<strong>th</strong> BMBR 565<br />
Ozonation (YMBR)<br />
665<br />
Oxygen cost for ozonation<br />
Ozonation (BMBR)<br />
Oxygen cost for ozonation<br />
118<br />
4,800<br />
565<br />
2,400
Chapter 5<br />
Conclusions and Recommendations<br />
This study investigated biological processes by using mixed yeast cultures and mixed<br />
b<strong>ac</strong>teria cultures for treating landfill le<strong>ac</strong>hate containing high organic and ammonium<br />
nitrogen concentrations. Basic studies on biokinetic coefficient <strong>of</strong> yeast and b<strong>ac</strong>teria sludge<br />
were carried out. The effects <strong>of</strong> high ammonium nitrogen on <strong>th</strong>e yeast and b<strong>ac</strong>teria sludge<br />
were evaluated using a respirometric me<strong>th</strong>od.<br />
The main part <strong>of</strong> <strong>th</strong>is study was focused on <strong>th</strong>e membrane biore<strong>ac</strong>tor. The potential<br />
for developing a membrane biore<strong>ac</strong>tor using mixed yeast sludge (YMBR) and mixed<br />
b<strong>ac</strong>teria sludge (BMBR) for treating raw le<strong>ac</strong>hate and stripped le<strong>ac</strong>hate was examined. The<br />
last section <strong>of</strong> <strong>th</strong>is study was focused on <strong>th</strong>e sludge properties, and membrane performance<br />
was investigated. The summary and conclusions drawn from <strong>th</strong>e experimental results are<br />
presented below.<br />
5.1 Conclusions<br />
1. In a membrane biore<strong>ac</strong>tor which was used to treat raw le<strong>ac</strong>hate, it was found <strong>th</strong>at <strong>th</strong>e<br />
average COD removal efficiency <strong>of</strong> <strong>th</strong>e YMBR was slightly higher <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e<br />
BMBR for varied HRT. The average COD removal efficiency in YMBR system was<br />
65±2% when HRT was in <strong>th</strong>e range <strong>of</strong> 16 to 24 h, whereas in BMBR system, <strong>th</strong>e<br />
average COD removal efficiency was 62±2% at <strong>th</strong>e same range <strong>of</strong> HRT. At HRT <strong>of</strong><br />
12 h, <strong>th</strong>e average COD removal efficiency in YMBR and BMBR were 60% and 51%,<br />
respectively. The decrease in removal efficiency in <strong>th</strong>e b<strong>ac</strong>terial system at a lower<br />
HRT was obviously seen. This can be due to <strong>th</strong>e presence <strong>of</strong> ammonia in <strong>th</strong>e le<strong>ac</strong>hate<br />
which posed toxicity to <strong>th</strong>e b<strong>ac</strong>terial culture. In addition to a better COD removal<br />
efficiency, YMBR was more stable <strong>th</strong>an BMBR. This could be considered as a<br />
specific advantage wi<strong>th</strong> <strong>th</strong>e yeast sludge over <strong>th</strong>e b<strong>ac</strong>teria sludge.<br />
2. The average TKN removal efficiency for bo<strong>th</strong> YMBR and BMBR systems, treating<br />
raw le<strong>ac</strong>hate at different HRT, was from 19-29% and 14-25%, respectively. The<br />
concentration <strong>of</strong> nitrite and nitrate (NO2 - and NO3 - ) in YMBR and BMBR effluents<br />
were in <strong>th</strong>e range <strong>of</strong> 0.8 to 6.4 mg/L and less <strong>th</strong>an 1.0 mg/L, respectively. This can be<br />
due to high organic and ammonium nitrogen concentrations and pH ranges.<br />
3. For <strong>th</strong>e ammonia striping process, <strong>th</strong>e average ammonia removal efficiency <strong>of</strong> 86%<br />
could be <strong>ac</strong>hieved <strong>th</strong>rough a stripping process carried out wi<strong>th</strong> a high speed velocity<br />
gradient (G) <strong>of</strong> 2,850 s -1 at pH from 11 to 12 for 5 h.<br />
4. In MBR which was used to treat stripped le<strong>ac</strong>hate, it was found <strong>th</strong>at <strong>th</strong>e fluctuations<br />
in terms <strong>of</strong> COD removal wi<strong>th</strong> ammonia stripping were lower <strong>th</strong>an <strong>th</strong>at wi<strong>th</strong>out<br />
ammonia stripping. The COD removal in bo<strong>th</strong> YMBR and BMBR wi<strong>th</strong> <strong>th</strong>e ammonia<br />
stripping was <strong>th</strong>e same. Bo<strong>th</strong> <strong>th</strong>e membrane re<strong>ac</strong>tors showed a COD removal <strong>of</strong> 72%<br />
at 16 h HRT and 76% at 24 h HRT. It was clear <strong>th</strong>at <strong>th</strong>e ammonia stripping improved<br />
<strong>th</strong>e performance <strong>of</strong> COD removal <strong>of</strong> <strong>th</strong>e BMBR much more <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e YMBR<br />
system as anticipated from <strong>th</strong>e toxicity studies. The BOD removal in bo<strong>th</strong> YMBR<br />
and BMBR systems was above 94%. This means <strong>th</strong>at <strong>th</strong>e membrane biore<strong>ac</strong>tors were<br />
119
efficient in <strong>th</strong>e removal <strong>of</strong> <strong>th</strong>e biodegradable organics in <strong>th</strong>e le<strong>ac</strong>hate. At 24 h HRT,<br />
<strong>th</strong>e range <strong>of</strong> BOD concentration was from 30 to 55 mg/L which followed <strong>th</strong>e present<br />
effluent standard. Bo<strong>th</strong> YMBR and BMBR effluents, contained low BOD/COD ratio<br />
indicated <strong>th</strong>at <strong>th</strong>ere were high refr<strong>ac</strong>tory organic substances, which may be due to <strong>th</strong>e<br />
contribution <strong>of</strong> <strong>th</strong>e slowly biodegradable organics and non-biodegradable organics,<br />
containing in <strong>th</strong>e raw le<strong>ac</strong>hate. Whereas, <strong>th</strong>e average TKN removal efficiency in all<br />
conditions was greater <strong>th</strong>an 80%.<br />
5. YMBR system gave significantly better reduction in <strong>th</strong>e membrane fouling rate <strong>th</strong>an<br />
BMBR system. The trend <strong>of</strong> membrane clogging in BMBR was higher <strong>th</strong>an in<br />
YMBR wi<strong>th</strong> correspondingly higher transmembrane pressure. However, YMBR<br />
might be operated wi<strong>th</strong> a relatively low pressure for a prolonged filtration cycle.<br />
Therefore, <strong>th</strong>e b<strong>ac</strong>teria membrane frequently requires cleaning. The average filtration<br />
time for <strong>th</strong>e yeast system was 1.3-2.5 times <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>teria system. As a result, yeast<br />
in a MBR re<strong>ac</strong>tor can enhance membrane performance and has <strong>th</strong>e potential to<br />
improve <strong>th</strong>e economics <strong>of</strong> treatment system because <strong>of</strong> <strong>th</strong>e reduction <strong>of</strong> operational<br />
problems and maintenance cost.<br />
6. For <strong>th</strong>e biokinetic study, a comparative evaluation <strong>of</strong> <strong>th</strong>e biokinetic parameters for<br />
bo<strong>th</strong> yeast and b<strong>ac</strong>teria sludge, which were used to treat le<strong>ac</strong>hate, illustrated <strong>th</strong>at <strong>th</strong>e<br />
maximum specific grow<strong>th</strong> rate (µmax) was less <strong>th</strong>an <strong>th</strong>e typical values for domestic<br />
wastewater whereas yield coefficient (Y) was still in <strong>th</strong>e range <strong>of</strong> domestic<br />
wastewater. Additionally, <strong>th</strong>e parametric group (µmax/Y.Ks) for yeast and b<strong>ac</strong>teria<br />
treating le<strong>ac</strong>hate were 1.77 x 10 -3 and 3.06 x 10 -3 L/mg.h, respectively. This<br />
indicated <strong>th</strong>at <strong>th</strong>e biodegradation <strong>of</strong> organics by yeast was less <strong>th</strong>an <strong>th</strong>at <strong>of</strong> b<strong>ac</strong>teria.<br />
It was confirmed <strong>th</strong>at <strong>th</strong>e biodegradation rates for bo<strong>th</strong> yeast and b<strong>ac</strong>teria in treating<br />
le<strong>ac</strong>hate were lower <strong>th</strong>an <strong>th</strong>at <strong>of</strong> domestic wastewater.<br />
7. The influence <strong>of</strong> ammonium nitrogen on a b<strong>ac</strong>teria culture was very sensitive,<br />
compared to a yeast culture. Also <strong>th</strong>e values <strong>of</strong> biokinetic coefficients show <strong>th</strong>at <strong>th</strong>e<br />
specific grow<strong>th</strong> rate in a b<strong>ac</strong>teria system was influenced by ammonium nitrogen. At<br />
ammonium nitrogen concentration <strong>of</strong> 2,000 mg/L, <strong>th</strong>e response <strong>of</strong> OUR inhibition in<br />
a b<strong>ac</strong>teria system was approximately 37%, whereas <strong>th</strong>at in a yeast system was around<br />
6%. Thus, <strong>th</strong>e ammonia concentration slightly affected <strong>th</strong>e yeast system but it<br />
inhibited <strong>th</strong>e microbial grow<strong>th</strong> in <strong>th</strong>e b<strong>ac</strong>terial system. Moreover, ammonia stripping<br />
was used to prevent <strong>th</strong>e inhibition <strong>of</strong> <strong>th</strong>e toxic compounds to <strong>th</strong>e organisms and to<br />
provide <strong>th</strong>e better efficiency <strong>of</strong> <strong>th</strong>e biological system.<br />
8. For <strong>th</strong>e effect <strong>of</strong> lead on OUR inhibition <strong>of</strong> b<strong>ac</strong>teria and yeast cultures, we found <strong>th</strong>at<br />
<strong>th</strong>e soluble lead concentration <strong>of</strong> 2.38 mg/L in b<strong>ac</strong>terial system showed 55%<br />
inhibition wi<strong>th</strong> non-linear correlation while <strong>th</strong>e soluble lead concentration <strong>of</strong> 1.50<br />
mg/L gave 50% inhibition wi<strong>th</strong> linear correlation in yeast system.<br />
9. The total membrane resistance (Rt) in <strong>th</strong>is study was depended mainly on a cake<br />
resistance (Rc). This might be due to <strong>th</strong>e cake layer deposited over <strong>th</strong>e membrane<br />
surf<strong>ac</strong>e. The formation <strong>of</strong> cake layer plays a major role in flux decline during<br />
filtration.<br />
10. The BOD5/COD <strong>of</strong> bo<strong>th</strong> YMBR and BMBR effluents was 0.01. Whereas, <strong>th</strong>e<br />
BOD20/COD ratio <strong>of</strong> <strong>th</strong>e YMBR and BMBR effluents varied wi<strong>th</strong> a ratio <strong>of</strong> 0.04 and<br />
120
0.02, respectively. This can be considered <strong>th</strong>at <strong>th</strong>e slowly degradable components in<br />
<strong>th</strong>e yeast effluent are higher <strong>th</strong>an <strong>th</strong>at in <strong>th</strong>e b<strong>ac</strong>terial effluent.<br />
11. The contribution <strong>of</strong> molecular weight compounds > 50 kDa in <strong>th</strong>e raw le<strong>ac</strong>hate was<br />
greater <strong>th</strong>an 80% in terms <strong>of</strong> BOD and COD concentrations. This found <strong>th</strong>at some<br />
portion <strong>of</strong> <strong>th</strong>e > 50 kDa compounds was broken down into < 5 kDa after ammonia<br />
stripping. The reduction <strong>of</strong> molecular weight compounds > 50 kDa significantly<br />
presented after MBR treatment. This showed <strong>th</strong>at <strong>th</strong>e complex higher molecular<br />
weight compounds could be degraded effectively using membrane biore<strong>ac</strong>tor<br />
systems. Considering <strong>th</strong>e BOD content in <strong>th</strong>e effluent, it was found <strong>th</strong>at in bo<strong>th</strong> yeast<br />
and b<strong>ac</strong>terial effluents, <strong>th</strong>e molecular weight compounds < 5 kDa contributed to <strong>th</strong>e<br />
maximum BOD when compared wi<strong>th</strong> <strong>th</strong>e o<strong>th</strong>er fr<strong>ac</strong>tions. The COD content also<br />
showed a similar trend.<br />
12. For <strong>th</strong>e sludge properties, <strong>th</strong>e bound and soluble EPS <strong>of</strong> <strong>th</strong>e yeast and b<strong>ac</strong>teria<br />
systems are measured. In comparison between yeast and b<strong>ac</strong>teria systems, bound<br />
EPS concentration in terms <strong>of</strong> TOC was not different while soluble EPS <strong>of</strong> mixed<br />
b<strong>ac</strong>terial sludge was higher <strong>th</strong>an <strong>th</strong>at <strong>of</strong> mixed yeast sludge. Also, <strong>th</strong>e protein to<br />
carbohydrate ratio in <strong>th</strong>e soluble EPS was higher. This indicated <strong>th</strong>at soluble EPS<br />
could be <strong>th</strong>e f<strong>ac</strong>tor which affected <strong>th</strong>e membrane fouling.<br />
13. The b<strong>ac</strong>terial sludge showed a better dewatering quality <strong>th</strong>an <strong>th</strong>at <strong>of</strong> <strong>th</strong>e yeast sludge.<br />
The viscosity <strong>of</strong> <strong>th</strong>e b<strong>ac</strong>terial system was higher <strong>th</strong>an <strong>th</strong>e yeast system.<br />
14. Ammonia stripping pretreatment wi<strong>th</strong> MBR was effective in treating le<strong>ac</strong>hate wi<strong>th</strong><br />
high ammonium nitrogen concentration but <strong>th</strong>e effluent still contained a large<br />
quantity <strong>of</strong> refr<strong>ac</strong>tory organic compounds. This might be due to <strong>th</strong>e contribution <strong>of</strong><br />
<strong>th</strong>e slowly biodegradable organics and non-biodegradable organics containing in <strong>th</strong>e<br />
le<strong>ac</strong>hate. Therefore, it should be fur<strong>th</strong>er treated in a post treatment, elevating <strong>th</strong>e<br />
water quality <strong>of</strong> <strong>th</strong>e final effluent or even increasing <strong>th</strong>e biodegradable organics<br />
5.2 Recommendations for Future Work<br />
Based on <strong>th</strong>e extensive experimental results <strong>of</strong> <strong>th</strong>is study, <strong>th</strong>e following<br />
recommendations are proposed.<br />
1. For MBR system, membrane fouling is a common problem but it is made more<br />
difficult to predict and control in <strong>th</strong>e MBR. This might be due to <strong>th</strong>e effects <strong>of</strong> <strong>ac</strong>tive<br />
microorganisms generating EPS. The EPS is <strong>of</strong> key significance wi<strong>th</strong> respect to<br />
fouling <strong>th</strong>at is dependent on <strong>th</strong>e EPS concentrations and chemical components <strong>of</strong><br />
EPS. Fouling is also affected by <strong>th</strong>e floc size and particle size distribution correlated<br />
wi<strong>th</strong> membrane permeability. It is recommended <strong>th</strong>at future work should be focused<br />
on <strong>th</strong>e contributions <strong>of</strong> <strong>th</strong>e various particle fr<strong>ac</strong>tions (suspended particles, colloidal,<br />
soluble solids), presenting in <strong>th</strong>e sludge on <strong>th</strong>e mechanisms <strong>of</strong> membrane fouling.<br />
More laboratory and pilot scale experiments are needed to estimate membrane<br />
fouling and <strong>th</strong>e influences <strong>of</strong> operating parameters.<br />
2. In MBR system, <strong>th</strong>e various soluble organic substances could be retained wi<strong>th</strong>in <strong>th</strong>e<br />
biore<strong>ac</strong>tor. The components <strong>of</strong> soluble organic compounds are complex and may<br />
include humic substances, fluvic <strong>ac</strong>ids, polys<strong>ac</strong>charides, proteins, etc. Therefore, <strong>th</strong>e<br />
121
MBR system should be explained <strong>th</strong>e behavior <strong>of</strong> <strong>th</strong>e <strong>ac</strong>cumulated soluble organic<br />
compounds. In addition, for better understanding <strong>of</strong> <strong>th</strong>e char<strong>ac</strong>teristics <strong>of</strong> organic<br />
substances in MBR, <strong>th</strong>e molecular weight distribution (MWD) and its compositions<br />
should be analyzed to investigate <strong>th</strong>e transformation <strong>of</strong> organic substances.<br />
3. It is well known <strong>th</strong>at landfill le<strong>ac</strong>hate, containing non-biodegradable and toxic<br />
organic compounds caused important environmental problems. Thus, <strong>th</strong>e degradation<br />
<strong>of</strong> refr<strong>ac</strong>tory organic compounds before and after treatments should be fur<strong>th</strong>er<br />
studied in terms <strong>of</strong> <strong>th</strong>e degradation <strong>of</strong> some substances such as <strong>th</strong>e degradation <strong>of</strong><br />
polycyclic aromatic hydrocarbons (PAHs), BTEX, aromatic hydrocarbon, aromatic<br />
ketone.<br />
4. Landfill le<strong>ac</strong>hate is a complex wastewater wi<strong>th</strong> considerable variation in bo<strong>th</strong> quality<br />
and quantity. The char<strong>ac</strong>teristics <strong>of</strong> le<strong>ac</strong>hate, particularly in terms <strong>of</strong> biodegradability,<br />
change as a landfill ages; it is difficult to treat le<strong>ac</strong>hate from a medium site and an<br />
old site using a one-stage membrane biore<strong>ac</strong>tor (MBR). Based on our encouraging<br />
results, <strong>th</strong>e treated le<strong>ac</strong>hate never<strong>th</strong>eless still contains <strong>th</strong>e refr<strong>ac</strong>tory organic<br />
compounds, which are difficult to degrade. Therefore, fur<strong>th</strong>er research should be<br />
performed on an advanced treatment such as nan<strong>of</strong>iltration, electrochemical<br />
oxidation, or photoassisted fenton me<strong>th</strong>ods to treat <strong>th</strong>e recalcitrant organic substances.<br />
These me<strong>th</strong>ods might elevate <strong>th</strong>e water quality <strong>of</strong> <strong>th</strong>e final effluent to meet <strong>th</strong>e<br />
present effluent standard. In addition, for better understanding <strong>of</strong> <strong>th</strong>e char<strong>ac</strong>teristics<br />
<strong>of</strong> organic substances in treated le<strong>ac</strong>hate, <strong>th</strong>e MWD and its compositions should be<br />
analyzed to indicate <strong>th</strong>e extent <strong>of</strong> organic removal in e<strong>ac</strong>h fr<strong>ac</strong>tion wi<strong>th</strong> HPLC, LC-<br />
MS for all treatments.<br />
5. There is a problem regarding foaming in <strong>th</strong>e MBR system due to inadequate dosage<br />
<strong>of</strong> antifoam chemicals. This should be controlled by using a peristaltic pump.<br />
122
References<br />
Abeling, U., and Seyfried, C.F., 1992. Anaerobic-Aerobic Treatment <strong>of</strong> High Streng<strong>th</strong><br />
Ammonium Wastewater- Nitrogen Removal via Nitrite. Water Science and <strong>Technology</strong>, 26<br />
(5-6): 1007-1015.<br />
Abeliovich, A., and Azov, Y., 1976. Toxicity <strong>of</strong> Ammonia to Algae in Sewage Oxidation<br />
Ponds. Apply Environmental Microbiology, 31: 801-806.<br />
Agamu<strong>th</strong>u, P., 1999. Char<strong>ac</strong>terization <strong>of</strong> Municipal Solid Waste and Le<strong>ac</strong>hate from<br />
Selected Landfills in Malaysia. Malaysian Journal <strong>of</strong> Science, 18: 99-103.<br />
Ahn, W.Y., Kang, M.S., Yim, S.K., and Choi, K.H., 1999. Nitrification <strong>of</strong> Le<strong>ac</strong>hate wi<strong>th</strong><br />
Submerged Membrane Biore<strong>ac</strong>tor: Pilot Scale. Proceedings IWA Conference Membrane<br />
<strong>Technology</strong> in environmental Management, Tokyo, Japan: 432-435.<br />
Ahn, W.Y., Kang, M.S., Yim, S.K., and Choi, K.H., 2002. Advanced Landfill Le<strong>ac</strong>hate<br />
Treatment Using an Integrated Membrane Process. Desalination, 149: 109-114.<br />
Albers, H., and Kruckeberg, G., 1992. Combination <strong>of</strong> Aerobic Pre-treatment, Carbon<br />
Adsorption and Coagulation. In: Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by Christensen, T.H.,<br />
Cossu, R., and Stegmann, R. Elsevier Science Publishers Ltd., England: ISBN: 1-85-<br />
166733-4: 305-312.<br />
Amokrane, A., Comel, C., and Vernon, J., 1997. Landfill Le<strong>ac</strong>hates Pre-treatment by<br />
Coagulation-Flocculation. Water Research, 31(11): 2775-2782.<br />
Andreux, F., 1979. Genese et Proprietes des Molecules Humiques. In Pedologie,<br />
Constituants et Proprietes du Sol, Paris, France: 97-122.<br />
Arnold, J.D., Knapp, J.S., and Johnson, C.L., 2000. The Use <strong>of</strong> Yeasts to Reduce <strong>th</strong>e<br />
Polluting Potential <strong>of</strong> Silage Effluent. Water Research, 34(15): 3699-3708.<br />
Andreottola, G., and Cannas, P., 1992. Chemical and Biological Char<strong>ac</strong>teristics <strong>of</strong> Landfill<br />
Le<strong>ac</strong>hate. In: Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by Christensen, T.H., Cossu, R., and<br />
Stegmann, R. Elsevier Science Publishers Ltd., England: ISBN: 1-85-166733-4: 65-88.<br />
APHA, AWWA, WPCF, 1998. Standard Me<strong>th</strong>ods for <strong>th</strong>e Examination <strong>of</strong> Water and<br />
Wastewater. 20 <strong>th</strong> Edition, Washington DC, USA. ISBN 0-87553-235-7.<br />
Avezzu, F., Bissolotti, G., and Collivignarelli, C., 1992. Combination <strong>of</strong> Wet Oxidation<br />
and Activated Sludge Treatment. In: Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by Christensen,<br />
T.H., Cossu, R., and Stegmann, R. Elsevier Science Publishers Ltd., England: ISBN: 1-85-<br />
166733-4: 333-352.<br />
Bae, J.H., Kim, S.K., and Chang, H.S., 1997. Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hates: Ammonia<br />
Removal via Nitrification and Denitrification and fur<strong>th</strong>er COD reduction via Fenton’s<br />
Treatment followed by Activated Sludge. Water Science and <strong>Technology</strong>, 36 (12): 341-<br />
348.<br />
123
Bae, B.U., Jung, E.S., Kim, Y.R., and Shin, H.S., 1999. Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate<br />
Using Activated Sludge Process and Electron-Beam Radiation. Water Research, 33(11):<br />
2669-2673.<br />
Barlaz, M.A., Ham, R.K., and Schaefer, D.M., 1989. Mass Balance Analysis <strong>of</strong><br />
Decomposed Refuse in Laboratory Scale Lysimeter. Journal <strong>of</strong> Environmental<br />
Engineering, ASCE 115: 1088-1102<br />
Barnes, D. and Bliss, P.J., 1983. Biological Control <strong>of</strong> Nitrogen in Wastewater Treatment.<br />
1 st Edition, E. & F. N. Spon, Ltd.: ISBN: 0-41-912350-4.<br />
Baumgarten, G., and Seyfried, C.F., 1996. Experiences and New Developments in<br />
Biological Pretreatment and Physical Post Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate. Water Science<br />
and <strong>Technology</strong>, 34(7-8): 445-453.<br />
Baun, A., Kl<strong>of</strong>t, L., Bjerg, P.L., and Nyholm, N., 1999. Toxicity Testing <strong>of</strong> Organic<br />
Chemicals in Groundwater Polluted wi<strong>th</strong> Landfill Le<strong>ac</strong>hate. Environmental Toxicology and<br />
Chemistry, 18(9): 2046-2053.<br />
Belfort, G., 1989. Membranes and Biore<strong>ac</strong>tors: A Technical Challenge in Biotechnology.<br />
Biotechnology and Bioengineering, 33: 1047-1066.<br />
Ben Aim, R.M., and Semmens, M.J., 2002. Membrane Biore<strong>ac</strong>tors for Wastewater<br />
Treatment and Reuse: A Success Story. Water Science and <strong>Technology</strong>, 47(1): 1-5.<br />
Bjorkman, V.B., and Mavinic, D.S., 1977. Physico-Chemical Treatment <strong>of</strong> a High Streng<strong>th</strong><br />
Le<strong>ac</strong>hate. Proceedings 32 nd Annual Industrial Waste Conference, Purdue University,<br />
Lafayeete, Indiana, USA: 189-195.<br />
Blakey, N.C., Cossu, R., Maris, P.J., and Mosey, F.E., 1992. Anaerobic Lagoons and<br />
UASB Re<strong>ac</strong>tors: Laboratory Experiments. In: Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by<br />
Christensen, T.H., Cossu, R., and Stegmann, R. Elsevier Science Publishers Ltd., England:<br />
ISBN: 1-85-166733-4: 245-263.<br />
Blum, D.J.W., and Speece, R.E., 1992. The Toxicity <strong>of</strong> Organic Chemicals to Treatment<br />
Processes. Water Science and <strong>Technology</strong>, 25(3): 23-31.<br />
Boyle, W.C., and Ham, R.K., 1974. Biological Treatability <strong>of</strong> Landfill Le<strong>ac</strong>hate. Journal<br />
<strong>of</strong> Water Pollution Control Federation, 46(5): 860.<br />
Bressi, G., and Favali, G., 1997. Uses <strong>of</strong> MBR (Membrane Biore<strong>ac</strong>tor) in Le<strong>ac</strong>hate<br />
Treatment. Proceedings Sardinia'97, 6 <strong>th</strong> International Waste Management and Landfill<br />
Symposium, Cagliari, Italy.<br />
Brockmann, M., and Seyfried, C.F., 1996. Sludge Activity and Cross-flow Micr<strong>of</strong>iltration-<br />
A Non Beneficial Relationship. Water Science and <strong>Technology</strong>, 34: 205-213.<br />
Brown, K., and Donnelly, K.C., 1988. An Estimation <strong>of</strong> <strong>th</strong>e Risk Associated wi<strong>th</strong> <strong>th</strong>e<br />
Organic Constituents <strong>of</strong> Hazardous and Municipal Waste Landfill Le<strong>ac</strong>hates. Hazardous<br />
Waste and Hazardous Materials, 5: 1-30.<br />
124
Brown, M.J., and Lester, J.N., 1980. Metal Removal in Activated Sludge: The Role <strong>of</strong><br />
B<strong>ac</strong>teria Extr<strong>ac</strong>ellular Polymers. Water Research, 13: 817-837.<br />
Bull, P.S., Evans, J.V., Wechsler, R.M., and Cleland, K.J., 1983. Biological <strong>Technology</strong> <strong>of</strong><br />
<strong>th</strong>e Treatment <strong>of</strong> Le<strong>ac</strong>hate from Sanitary Landfills. Water Research, 17(11): 1473-1481.<br />
Bura, R, Cheung, M., Liao, B., Finlayson, J., Lee, B.C., Droppo, I.G., Leppard, G.G., and<br />
Liss, S.N., 1998. Composition <strong>of</strong> Extr<strong>ac</strong>ellular Polymeric Substances in <strong>th</strong>e Activated<br />
Sludge Matrix. Water Science and <strong>Technology</strong>, 37: 325-333.<br />
Cairns, J., and Van Der Schalie, W.H., 1980. Biological Monitoring Part I- Early Warning<br />
Systems. Water Research, 14: 1179-1196.<br />
Cameron, R.D., and Koch, F.A., 1980. Tr<strong>ac</strong>e Metals and Anaerobic Digestion <strong>of</strong> Le<strong>ac</strong>hate.<br />
Journal <strong>of</strong> Water Pollution Control Federation, 52(2): 282.<br />
Chae, K.J., Oh, S.E., Lee, S.T., and Kim, I.S., 1999. Biological Le<strong>ac</strong>hate Treatment by<br />
Pure-Oxygen Aeration and Modeling <strong>th</strong>e Removal <strong>of</strong> Organics. Journal <strong>of</strong> Korean Society<br />
<strong>of</strong> Environmental Engineering, 21(10): 1891-1900.<br />
Chaing, L.C., Chang, J.E., and Wen, T.C., 1995. Indirect Oxidation Effect in<br />
Electrochemical Oxidation Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate. Water Research, 29(2): 671-<br />
678.<br />
Chang, I. S., Kim, J.S., and Lee, C.H., 1996. Membrane Bi<strong>of</strong>ouling Char<strong>ac</strong>teristics in<br />
Membrane Coupled Activates Sludge System. Proceeding <strong>of</strong> ICOM, Yokohama, Japan:<br />
926-927.<br />
Chang, I.S., and Lee, C.H., 1998. Membrane Filtration Char<strong>ac</strong>teristics in Membrane<br />
Coupled Activated Sludge System-The Effect <strong>of</strong> Physiological States <strong>of</strong> Activated Sludge<br />
on Membrane Fouling. Desalination, 120: 221-233.<br />
Chang, I.S., and Lee, C.H., 2001. The effects <strong>of</strong> EPS on Membrane Fouling in <strong>th</strong>e MBR<br />
Process. Proceedings MBR3 Conference, England: 19-28.<br />
Chen, C.Y., Huang, J.B., and Chen, S.D., 1997. Assessment <strong>of</strong> <strong>th</strong>e Microbial Toxicity Test<br />
and Its Application for Industrial Wastewater. Water Science and <strong>Technology</strong>, 36(12): 375-<br />
382.<br />
Cheung, K.C., Chu, L.M., and Wong, H.M., 1993. Toxic Effect <strong>of</strong> Landfill Le<strong>ac</strong>hate on<br />
Microalgae. Water Air and Soil Pollution, 69: 337-349.<br />
Cheung, K.C., Chu, L.M., and Wong, M.H., 1997. Ammonia Stripping as a Pre-treatment<br />
for Landfill Le<strong>ac</strong>hate. Water, Air and Soil Pollution, 94: 209-221.<br />
Chian, E.S.K. and DeWalle, F.B., 1976. Sanitary Landfill Le<strong>ac</strong>hjate and Their Treatment.<br />
Journal <strong>of</strong> <strong>th</strong>e Environmental Engineering Division, ASCE, 102: 411-431.<br />
Chian, E.S.K., 1977. Stability <strong>of</strong> Organic Matter in Landfill Le<strong>ac</strong>ahtes. Water Research,<br />
11(2): 225-232.<br />
125
Chian, E.S.K., and DeWalle, F.B., 1977. Treatment <strong>of</strong> High Streng<strong>th</strong> Acidic Wastewater<br />
wi<strong>th</strong> a Completely Mixed Anaerobic Filter. Water Research, 11: 295-304.<br />
Chiang, L.C., Chang, J.E., and Wen, T.C., 1995. Indirect Oxidation Effect in<br />
Electrochemical Oxidation Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate. Water Research, 29(2): 671-<br />
678.<br />
Chigusa, K., Hasegawa, T., Yamamoto, N., and Watanabe, Y., 1996. Treatment <strong>of</strong><br />
Wastewater from Oil Manuf<strong>ac</strong>turing Plant by Yeasts. Water Science and <strong>Technology</strong>,<br />
34(11): 51-58.<br />
Cicek, N., Franco, P., Suidan, M., Urbain, V., and Manem, J., 1999. Char<strong>ac</strong>terization and<br />
Comparison <strong>of</strong> a Membrane Biore<strong>ac</strong>tor and a Conventional Activated Sludge System in <strong>th</strong>e<br />
Treatment <strong>of</strong> Wastewater Containing High Molecular Weight Compounds. Water<br />
Environmental Research, 71: 64-70.<br />
Clement, B., Persoone, G., Janssen, C., and Le Du-Delepierre, A., 1996. Estimation <strong>of</strong> <strong>th</strong>e<br />
Hazard <strong>of</strong> Landfills Through Toxicity Testing <strong>of</strong> Le<strong>ac</strong>hates: 1. Determination <strong>of</strong> Le<strong>ac</strong>hate<br />
Toxicity wi<strong>th</strong> a Battery <strong>of</strong> Acute Tests. Chemosphere, 33: 2303-2320.<br />
Cook, E.N., and Foree, E.G., 1974. Aerobic Bio-stabilization <strong>of</strong> Sanitary Landfill<br />
Le<strong>ac</strong>hate. Journal <strong>of</strong> Water Pollution Control Federation, 46(2): 380-392.<br />
Cossu, R., Polcaro, A.M., Lavagnolo, M.C., Mascia, M., Palmas, S., and Renold, F., 1998.<br />
Electrochemical Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate: Oxidation at Ti/PbO2 and Ti/SnO2<br />
Anodes. Environmental Science and <strong>Technology</strong>, 32: 3570-3573.<br />
Cossu, R., Serra, R., and Muntoni, A., 1992. Physico-Chemical Treatment <strong>of</strong> Le<strong>ac</strong>hate. In:<br />
Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by Christensen, T.H., Cossu, R., and Stegmann, R.<br />
Elsevier Science Publishers Ltd., England: ISBN: 1-85-166733-4: 265-304.<br />
Cui, Q., and Tang, C., 2000. Effects <strong>of</strong> Lead and Selenium on Yeast (S<strong>ac</strong>charomyces<br />
Cerevisiae) Telomere. Journal <strong>of</strong> Environmental Science and Heal<strong>th</strong>, Part A:<br />
Toxic/Hazardous Substances and Environmental Engineering, 35(9): 1663-1671.<br />
Dan, N.P., 2002. Biological Treatment <strong>of</strong> High Salinity Wastewater Using Yeast and<br />
B<strong>ac</strong>teria Systems. Dissertation, <strong>Asian</strong> <strong>Institute</strong> <strong>of</strong> <strong>Technology</strong>, Thailand.<br />
Dan, N.P., Visvana<strong>th</strong>an, C., Polprasert, C., and Aim, R.B., 2002. High Salinity<br />
Wasterwater Treatment Using Yeast and B<strong>ac</strong>teria Membrane Biore<strong>ac</strong>tors. Water Science<br />
and <strong>Technology</strong>, 46(9): 201-209.<br />
Defrance, L., Jaffrin, M.Y., Gupta, B., Paullier, P., and Geaugey, V., 2000. Contribution <strong>of</strong><br />
Various Constituents <strong>of</strong> Activated Sludge to Membrane Biore<strong>ac</strong>tor Fouling. Bioresource<br />
<strong>Technology</strong>, 73: 105-112<br />
Defrance, M.B., 1993. Etude d’un Re<strong>ac</strong>tor Levurien Pour le Tr<strong>ait</strong>ement des Effluents<br />
d’Industries Alimentairs. Doctoral <strong>Thesis</strong>, University <strong>of</strong> Montpellier II-Sciences et<br />
Techniques du Languedoc, France.<br />
126
Diamadopoulos, E., 1994. Char<strong>ac</strong>terization and Treatment <strong>of</strong> Recirculation-Stabilized<br />
Le<strong>ac</strong>hate. Water Research, 28(12): 2439-2445.<br />
Dichtl, N., Dockhorn, T., and Wittenberg, M., 2001. Investigations Comparing SBR<br />
Re<strong>ac</strong>tors and Continuous Flow Plants for <strong>th</strong>e Nitrification <strong>of</strong> Landfill Le<strong>ac</strong>hate.<br />
Proceedings Sardinia’ 01, 8 <strong>th</strong> International Waste Management and Landfill Symposium,<br />
Cagliari, Italy.<br />
Dign<strong>ac</strong>, M.F., Urbain, V., Ryb<strong>ac</strong>ki, D., Bruchet, A., Snidaro, D., and Scribe, P., 1998.<br />
Chemical Description <strong>of</strong> Extr<strong>ac</strong>ellular Polymers: Implication on Activated Sludge Floc<br />
Structure. Water Science and <strong>Technology</strong>, 38: 45-53<br />
Dijk, L., and Roncken, G.C.G., 1997. Membrane Biore<strong>ac</strong>tor for Wastewater Treatment:<br />
The State <strong>of</strong> <strong>th</strong>e Art and New Developments. Water Science and <strong>Technology</strong>, 35(10): 35-<br />
41.<br />
Dollerer, J., and Wilderer, P.A., 1996. Biological Treatment <strong>of</strong> Le<strong>ac</strong>hates from Hazardous<br />
Waste Landfills Using SBBR <strong>Technology</strong>. Water Science and <strong>Technology</strong>, 34(7-8): 437-<br />
444.<br />
Doyle, J., Watts, S., Solley, D., and Keller, J., 2001. Exceptionally High-rate Nitrification<br />
in Sequencing Batch Re<strong>ac</strong>tors Treating High Ammonia Landfill Le<strong>ac</strong>hate. Water Science<br />
and <strong>Technology</strong>, 43 (3): 315-322.<br />
Dubois, M.J., Gilles, K.A., Hamilton, J.K., Reber, P.A., and Smi<strong>th</strong>, F., 1956. Colorimetric<br />
Me<strong>th</strong>od for Determination <strong>of</strong> Sugars and Related Substances. Analytical Chemistry, 28(3):<br />
350-356.<br />
Dzombak, D.A., Langnese, K.M., Spengel, D.B., and Lu<strong>th</strong>y, R.G., 1990. Comparison <strong>of</strong><br />
Activated Sludge and RBC Treatment <strong>of</strong> Le<strong>ac</strong>hate from a Solid Waste Landfill.<br />
Proceeding <strong>of</strong> 1990 WPCF National Specialty Conference on water quality Management<br />
<strong>of</strong> Landfills, July 15-18, Chicago, USA: 4-39-4-58.<br />
Ehrig, H.J., 1983. Quality and Quantity <strong>of</strong> Sanitary Landfill Le<strong>ac</strong>hate. Waste Management<br />
and Research, 1: 53-68.<br />
Ehrig, H.J., 1998. Water and Element Balances <strong>of</strong> Landfills, Lecture Notes in Ear<strong>th</strong><br />
Sciences, Edited by B<strong>ac</strong>cini, P., Springer-Verlag, Berlin, Germany.<br />
Ekama, G.A., Dold, P.L., and Marais, G.V.R., 1986. Procedures for Determining Influent<br />
COD Fr<strong>ac</strong>tions and <strong>th</strong>e Maximum Specific Grow<strong>th</strong> Rate <strong>of</strong> Heterotrophs in Activated<br />
Sludge System. Water Science and <strong>Technology</strong>, 18(6): 91-114.<br />
Elmaleh, S., Defrance, M.B., Ghommidh, C., and Navarro, J.M., 1996. Technical Note:<br />
Acidogenic Effluents Treatment in a Yeast Re<strong>ac</strong>tor. Water Research, 30(10): 2526-2529.<br />
Fairwea<strong>th</strong>er, R.J., and Barlaz, M.A., 1988. Hydrogen Sulphide Production During<br />
Decomposition <strong>of</strong> Landfill Inputs. Journal <strong>of</strong> Environmental Engineering, ASCE, 124:<br />
353-361.<br />
127
Fan, X., Urbain, V., Qian, Y., and Manem, J., 1996. Nitrification and Mass Balance wi<strong>th</strong><br />
MBR for Municipal Wastewater Treatment. Submitted for <strong>th</strong>e 1996 IAWQ Biennial<br />
Conference, Singapore.<br />
Fane, A.G., Fell, C.J.D., and Nor, M.T., 1981. Ultrafiltration Activated Sludge System-<br />
Development <strong>of</strong> a Predictive Model. Polymer Science <strong>Technology</strong>, 13: 631-658.<br />
Farquhar, G.J., 1989. Le<strong>ac</strong>hate: Production and Char<strong>ac</strong>teristics. Canadian Journal <strong>of</strong> Civil<br />
Engineering, 16: 317-325.<br />
Fettig, J., Stapel, H., Steinert , C., and Geiger, M., 1996. Treatment <strong>of</strong> landfill le<strong>ac</strong>hate by<br />
preozonation and adsorption in <strong>ac</strong>tivated carbon columns. Water Science and <strong>Technology</strong>,<br />
34 (9):33–40.<br />
Fisher, M., and Fell, C., 1999. Ammonia Removal from High Streng<strong>th</strong> Le<strong>ac</strong>hate Using a<br />
Sequencing Batch Re<strong>ac</strong>tor. Waste Management, 25-26.<br />
Flemming, H.C., and Wingender, J., 2001. Relevant <strong>of</strong> Microbial Extr<strong>ac</strong>ellular Polymeric<br />
Substances-Part II: Technical aspects. Water Science and <strong>Technology</strong>, 43(6): 9-16.<br />
Garcia, H., Rico, J.L., and Garcia, P.A., 1996. Comparison <strong>of</strong> Anaerobic Treatment <strong>of</strong><br />
Le<strong>ac</strong>hates from an Urban-Solid-Waste Landfill at Ambient Temperature and at 35 o C.<br />
Bioresource <strong>Technology</strong>, 58: 273-277.<br />
Gau, S.H. and Chang, F.S., 1996. Improved Fenton Me<strong>th</strong>od to Remove Recalcitrant<br />
Organics in Landfill Le<strong>ac</strong>hate. Water Science and <strong>Technology</strong>, 34(7-8); 455-462.<br />
Gaudy, A.F., Rozich, A., and Garniewski, S., 1986. Treatability Study <strong>of</strong> High Streng<strong>th</strong><br />
Landfill Le<strong>ac</strong>hate. Proceedings <strong>of</strong> <strong>th</strong>e 41 st Industrial Waste Conference, Purdue University,<br />
Indiana, USA: 627-638.<br />
Geenens, D., Bixio, D., and Thoeye, C., 1999. Advanced Oxidation Treatment <strong>of</strong> Landfill<br />
Le<strong>ac</strong>hate. Proceedings Sardinia’99, 7 <strong>th</strong> International Waste Management and Landfill<br />
Symposium, Cagliari, Italy.<br />
Ghyoot, W., Vandaele, S., and Verstraete, W., 1999. Nitrogen Removal from Sludge<br />
Reject Water wi<strong>th</strong> a Membrane Assisted Biore<strong>ac</strong>tor. Water Research, 33: 23-32.<br />
Gierlich, H., and Kollb<strong>ac</strong>h, J., 1998. Treating Landfill Le<strong>ac</strong>hate in European Countries.<br />
Pollution Engineering International: 10-14.<br />
Goodwin, J.A.S., and Foster, C.F., 1985. A Future Examination into <strong>th</strong>e Composition <strong>of</strong><br />
Activated Sludge Surf<strong>ac</strong>es in Relation to Their Settlement Char<strong>ac</strong>teristics. Water Research,<br />
19: 527-533.<br />
Gourdon, R., Comel, P., Vermande, P., and Veron, J., 1989. Fr<strong>ac</strong>tionate <strong>of</strong> <strong>th</strong>e Organic<br />
Matter <strong>of</strong> a Landfill Le<strong>ac</strong>hate before and after Aerobic or Anaerobic Biological Treatment.<br />
Water Research, 23(2): 167-173.<br />
128
Grady, C.P.L., Daigger, G.T., and Lim, H.C., 1999. Biological Wastewater Treatment. 2 nd<br />
Edition, Marcel Dekker, Inc.: ISBN: 0-82-478919-9.<br />
Graham, D.W., 1981. Biological-Chemical Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate. Department <strong>of</strong><br />
Civil Engineering, University <strong>of</strong> British Columbia, Canada.<br />
Graham, D.W., and Mavinic, D.S., 1979. Biological-Chemical Treatment <strong>of</strong> Le<strong>ac</strong>hate.<br />
Proceedings <strong>of</strong> <strong>th</strong>e American Society <strong>of</strong> Civil Engineers National Conference on<br />
Environmental Engineering, San Francisco, USA: 291-298.<br />
Guell, C., Czekaj, P., and Davis, R.H., 1999. Micr<strong>of</strong>iltration <strong>of</strong> Protein Mixtures and <strong>th</strong>e<br />
Effects <strong>of</strong> Yeast on Membrane Fouling. Journal <strong>of</strong> Membrane Science, 155(1): 113-122.<br />
Gunder, B., 2001. The Membrane Coupled Activated Sludge Process in Municipal<br />
Wastewater Treatment. Technomic Publishing Co., Inc., USA: ISBN: 1-56-676959-0.<br />
Gurijala, K.R., and Suflita, J.A., 1993. Environmental f<strong>ac</strong>tors influencing me<strong>th</strong>anogenesis<br />
from refuse in landfill samples. Environmental Science and technology, 27:1176-1181.<br />
Hall, E.R., Onysko, K.A., and Parker, W.J., 1995. Enhancement <strong>of</strong> Ble<strong>ac</strong>hed Kraft<br />
Organo-chlorine Removal by Coupling Membrane Filtration and Anaerobic Treatment.<br />
Environmental <strong>Technology</strong>, 16: 115-126.<br />
Hanaki, K., Wantawin, C., and Ohgaki, S., 1990. Effects <strong>of</strong> <strong>th</strong>e Activity <strong>of</strong> Heterotrophs on<br />
Nitrification in a Suspended Grow<strong>th</strong> Re<strong>ac</strong>tor. Water Research, 24(3): 289-296.<br />
Harmsen, J., 1983. Identification <strong>of</strong> Organic Compounds in Le<strong>ac</strong>hate from a Waste Tip.<br />
Water Research, 17(6): 699-705.<br />
Henderson, J.P., Besler, D.A., Atwater, J.A., and Mavinic, D., 1997. Treatment <strong>of</strong><br />
Me<strong>th</strong>anogenic Landfill Le<strong>ac</strong>hate to Remove Ammonia Using a Rotating Biological<br />
Cont<strong>ac</strong>tor (RBC) and a Sequencing Batch Re<strong>ac</strong>tor (SBR). Environmental <strong>Technology</strong>,<br />
18(7): 687-698.<br />
Henry J. G., Prasad, D., Sidhwa, R., and Hilgerdenaar, M., 1982. Treatment <strong>of</strong> Landfill<br />
Le<strong>ac</strong>hate by Anaerobic Filter. Water Pollution Research Journal <strong>of</strong> Canada, 17: 45-56.<br />
Henry, J.G., 1985. New Developments in Landfill Le<strong>ac</strong>hate Treatment. Proceedings <strong>of</strong><br />
International Conference on New Directions and Research in Waste Treatment and<br />
Residuals Management, University <strong>of</strong> British Columbia, USA: 1-139.<br />
Henry, J.G., Prasad, D., and Young, H., 1987. Removal <strong>of</strong> Organics from Le<strong>ac</strong>hates by<br />
Anaerobic Filter. Water Research, 21(11): 1395-1399.<br />
Henze, M., 1992. Char<strong>ac</strong>terization <strong>of</strong> Wastewater for Modelling Activated Sludge<br />
Processes. Water Science and <strong>Technology</strong>, 25(6): 1-15.<br />
Ho, S., Boyle, W.C., and Ham, R.K., 1974. Chemical treatment <strong>of</strong> Le<strong>ac</strong>hates from<br />
Sanitary Landfills, Journal <strong>of</strong> Water Pollution Control Federation, 46(7), 1776-1791.<br />
129
Hosomi, M., Matsusige, K., Inamori, Y., Sudo, R., Yamada, K., and Yoshino, Z., 1989.<br />
Sequencing Batch Re<strong>ac</strong>tor Activated Sludge Processes for <strong>th</strong>e Treatment <strong>of</strong> Municipal<br />
Landfill Le<strong>ac</strong>hate: Removal <strong>of</strong> Nitrogen and Refr<strong>ac</strong>tory Organic Compounds. Water<br />
Science and <strong>Technology</strong>, 21: 1651-1654.<br />
Hu, T., 1989. Treatment <strong>of</strong> Vermicelli Wastewater by an Acid-tolerant, Starch Degrading<br />
Yeast. Biological Waste, 28(3): 163-174.<br />
Huang, X., Liu, R., and Qian, Y., 2000. Behaviour <strong>of</strong> Soluble Microbial Products in a<br />
Membrane Biore<strong>ac</strong>tor. Process Biochemistry, 36: 401-406.<br />
Illies, P., 1999. Biological Nitrification and Denitrification <strong>of</strong> High Ammonia Landfill<br />
Le<strong>ac</strong>hate Using Pre and Post Treatment Denitrification Systems and Me<strong>th</strong>anol as<br />
Supplementary Source <strong>of</strong> Organic Carbon. Master <strong>Thesis</strong>, University <strong>of</strong> British Columbia,<br />
Canada.<br />
Imai, A., Iwami, N., Matsushige, K., Inamori, Y., and Sudo, R., 1993. Removal <strong>of</strong><br />
Refr<strong>ac</strong>tory Organics and Nitrogen from Landfill Le<strong>ac</strong>hate by <strong>th</strong>e Microorganism-Att<strong>ac</strong>hed<br />
Activated Carbon Fluidised Bed Process. Water Research, 27(1): 143-145.<br />
Imai, A., Onuma, K., Inamori, Y., and Sudo, R., 1995. Biodegradation and Adsorption in<br />
Refr<strong>ac</strong>tory Le<strong>ac</strong>hate Treatment by <strong>th</strong>e Biological Activated Carbon Fluidized Bed Process.<br />
Water Research, 29(2): 687-694.<br />
Jans, J.M., Schroeff, A.V.D and Jaap, A., 1992. Combination <strong>of</strong> UASB Pre-treatment and<br />
Reverse Osmosis. In: Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by Christensen, T.H., Cossu, R.,<br />
and Stegmann, R. Elsevier Science Publishers Ltd., England: ISBN: 1-85-166733-4: 313-<br />
321.<br />
Jensen, J.C., Cameron, D.H., and Penny, J.P., 2001. Operating Experience wi<strong>th</strong> Innovative<br />
High Efficiency Membrane Treatment <strong>of</strong> Landfill Le<strong>ac</strong>ahte. The 6 <strong>th</strong> Annual symposium by<br />
Waste Association <strong>of</strong> Nor<strong>th</strong> America (SWANA).<br />
Jonard, Z., Zartarian, F., Thomas, F., Block, J.C., Bottero, J.Y., Villemin, G., Urbain, V.,<br />
and Manem, J., 1995. Chemical and Structural (2D) Linkage between B<strong>ac</strong>teria wi<strong>th</strong>in<br />
Activated Sludge Flocs. Water Research, 29: 1639-1647.<br />
Kabdasli, I., Tunay, O., Ozturk, I., Yilmaz, S., and Arikan, O., 2000. Ammonia Removal<br />
from Young Landfill Le<strong>ac</strong>hate by Magnesium Ammonium Phosphate Precipitation and Air<br />
Stripping. Water Science and <strong>Technology</strong>, 41(10): 237-240.<br />
Kang, K.H., Shin, H.S., and Park, H., 2002. Char<strong>ac</strong>terization <strong>of</strong> Humic Substances Present<br />
in Landfill Le<strong>ac</strong>hates wi<strong>th</strong> Different Landfill Ages and Its Implications. Water Research,<br />
36: 4023-4032.<br />
Kappeler, J., and Gujer, W., 1992. Estimation <strong>of</strong> Kinetic Parameters <strong>of</strong> Heterotrophic<br />
Biomass under Aerobic Conditions and Char<strong>ac</strong>terization <strong>of</strong> Wastewater for Activated<br />
Sludge Modelling. Water science and technology, 25(6): 125-139.<br />
130
Keenan, J.D., Steiner, R.L., and Fungaroli, A.A., 1984. Landfill Le<strong>ac</strong>hate Treatment.<br />
Journal <strong>of</strong> Water Pollution Control Federation, 56(1): 27-33.<br />
Kennedy K. J., Hamoda M. F., and Guiot S. G., 1988. Anaerobic Treatment <strong>of</strong> Le<strong>ac</strong>hate<br />
using Fixed Film and Sludge Bed Systems. Journal <strong>of</strong> Water Pollution Control Federation,<br />
60:1675-1683.<br />
Kennedy, K., and Lentz, E., 2000. Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate Using Sequencing Batch<br />
and Continuous Flow Upflow Anaerobic Sludge Blanket (UASB) Re<strong>ac</strong>tors. Water<br />
Research, 34(14): 3640-3656.<br />
Kettunen, R.H., Hoilijoki, T.H., and Rintala, J.A., 1996. Anaerobic and Sequential<br />
Anaerobic-Aerobic Treatment <strong>of</strong> Municipal Landfill Le<strong>ac</strong>hate at Low Temperature.<br />
Bioresource <strong>Technology</strong>, 58(1): 31-40.<br />
Kim, C.W., Kim, B. G., Lee, T.H., and Park, T.J., 1994. Continuous and Early Detection <strong>of</strong><br />
Toxicity in Industrial Wastewater Using an On-line Respiration Meter, Water Science and<br />
<strong>Technology</strong>, 30(3): 11-19.<br />
Kim, J.S., Lee, C.H., and Chang, I.S., 2001. Effect <strong>of</strong> Pump Shear on <strong>th</strong>e Performance <strong>of</strong> a<br />
Crossflow Membrane Biore<strong>ac</strong>tor. Water Research, 35: 2137-2144.<br />
Kim, J.S., Lee, C.H., and Chun, H.D., 1998. Comparison <strong>of</strong> Ultrafiltration Char<strong>ac</strong>teristics<br />
between Activated Sludge and BAC Sludge. Water Research, 32: 3443-3451.<br />
Kim, S.M., Geissen, S.U., and Vogelpohl, A., 1997. Landfill le<strong>ac</strong>hate Treatment by a<br />
Photoassisted Fenton Re<strong>ac</strong>tion. Water Science and <strong>Technology</strong>, 35(4): 239-248.<br />
Knox, K., and Jones, P.H., 1979. Complexation Char<strong>ac</strong>teristics <strong>of</strong> Sanitary Landfill<br />
Le<strong>ac</strong>hates. Water Research, 27: 405-411.<br />
Knox, K., 1985. Le<strong>ac</strong>hate Treatment wi<strong>th</strong> Nitrification <strong>of</strong> Ammonia. Water Research, 19<br />
(7): 895-904.<br />
Krau<strong>th</strong>, K.H., and Staab, K.F., 1993. Pressurized Biore<strong>ac</strong>tor wi<strong>th</strong> Membrane Filtration for<br />
Wastewater Treatment. Water Research, 27: 405-411.<br />
Krug A.T., and Mcdougall, S., 1988, Preliminary <strong>of</strong> a Micr<strong>of</strong>iltration/Reverse Osmosis<br />
Process for <strong>th</strong>e Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate. Environmental Ontario Environmental<br />
Research <strong>Technology</strong> Transfer Conference, 28-29 Nov, Toronto, Canada.<br />
Kylefors, K., 1997. Landfill Le<strong>ac</strong>hate Management- Short and Long Term Perspectives.<br />
Luleå University <strong>of</strong> <strong>Technology</strong>, Sweden: ISSN: 1402-1757.<br />
LaGrega, M.D., Buckingham, P.L., and Evans, J.C., 1994. Hazardous Waste Management.<br />
McGraw-Hill, USA: 0-07-019552-8.<br />
Leckie, J.O., P<strong>ac</strong>ey, J.G., and Halvadakis, C., 1975. Acceleration Refuse Stabilization<br />
Through Controlled Moisture Application. Paper Presented in <strong>th</strong>e 2 nd Annual National<br />
Environmental Engineering Research Development and Design, Gainsville, Florida, USA.<br />
131
Leckie, J.O., P<strong>ac</strong>ey, J.G., and Halvadakis, C., 1979. Landfill Management wi<strong>th</strong> Moisture<br />
Control. Journal Environmental Engineering Division, ASCE, 105(EE2): 337-355.<br />
Lecoupannce, F., 1999. Fr<strong>ac</strong>tionnement et Car<strong>ac</strong>terisation des Lixiviats de Centres<br />
D’enfouissement de D’echets Menagers par Chromatographie Liquide (Fr<strong>ac</strong>tionation and<br />
Char<strong>ac</strong>terization <strong>of</strong> Sanitary Landfill Le<strong>ac</strong>hates by Liquid Chromatography). Ph.D.<br />
<strong>Thesis</strong>, Universite de Bretagne-Sud, France.<br />
Lee, C.J., 1979. Treatment <strong>of</strong> Municipal Landfill Le<strong>ac</strong>hate. Master <strong>Thesis</strong>, University <strong>of</strong><br />
British Columbia, Canada.<br />
Lema, J.M., Mendez, R., and Blazquez, R., 1988. Char<strong>ac</strong>teristics <strong>of</strong> Landfill Le<strong>ac</strong>hates and<br />
Alternatives for Their Treatment: A Review. Water, Air and Soil Pollution, 40: 223-250<br />
Liao, B.Q., Allen, D.G., Droppo, I.G., Leppard, G.G., and Liss, S.N., 2001. Surf<strong>ac</strong>e<br />
Properties <strong>of</strong> Sludge and Their Role in Bi<strong>of</strong>locculation and Settleability. Water Research,<br />
35: 339-350.<br />
Liebeskind, M., 1999. Parameter for Dynamic Simulate <strong>of</strong> Municipal Sewage Treatment<br />
Plant (German). Gewaessersghutz Wasser Abwasser No 171, A<strong>ac</strong>hen Technical University.<br />
Lin, S.H., and Chang, C.C., 2000. Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate by Combined Electro-<br />
Fenton Oxidation and Sequencing Batch Re<strong>ac</strong>tor Me<strong>th</strong>od. Water Research, 34(17): 4243-<br />
4249.<br />
Lowry, O.H., Resebrough, N.J., Farr, A.L., and Randall, R., 1951. Protein Measurement<br />
wi<strong>th</strong> <strong>th</strong>e Folin Phenol Rreagent. Journal <strong>of</strong> Biological Chemistry, 193: 265-275.<br />
Lubbecke, S., Vogelpohl, A., and Dewjanin, W., 1995. Wastewater Treatment in a<br />
Biological High-Performance System wi<strong>th</strong> High Biomass Concentration. Water Research,<br />
29: 793-802.<br />
Madoni, P., Davoli, D., and Guglielmf, L., 1999. Response <strong>of</strong> SOUR and AUR to Heavy<br />
Metal Contamination in Activated Sludge, Water Research, 33(10): 2459-2464.<br />
Madoni, P., Davoli, D., Gorbi, G., and Vescovi, L., 1996. Toxic Effect <strong>of</strong> Heavy Metals on<br />
<strong>th</strong>e Activated Sludge Protozoan Community, Water Research, 30: 135-141.<br />
Mallevialle, J., Odendaal, P.E., and Wiesner, M.R., 1996. Water Treatment Membrane<br />
Processes. McGraw-Hill, USA: ISBN: 0-07-001559-7.<br />
Mandra, V., Amar, D., Trouve, E., Courant, P., and Coulomb, I., 1995. Membrane<br />
Biore<strong>ac</strong>tor and Reverse Osmosis Coupling for <strong>th</strong>e Treatment <strong>of</strong> Discharge Le<strong>ac</strong>hates.<br />
Proceedings <strong>of</strong> International Workshop Membrane in Drinking Water Production,<br />
International Water Supply Association, Paris, France: 33-38.<br />
Manem, J., 1993. Membrane Biore<strong>ac</strong>tors for Wastewater Treatment and Drinking Water<br />
Production. Proceedings <strong>of</strong> <strong>th</strong>e 3 rd World Congress <strong>of</strong> <strong>th</strong>e World Federation <strong>of</strong><br />
Engineering Organizations, Beijing, China: 907-914.<br />
132
Martin, G.M.A., Auzmenti, A.I., and Olozaga, C.P., 1995. Landfill Le<strong>ac</strong>hate: Variation in<br />
Quality and Quantity. Proceedings <strong>of</strong> Sardinia’ 95, 5 <strong>th</strong> International Landfill Symposium,<br />
Cagliari, Italy: 345-354.<br />
Marttinen, S.K., Kettunen, R.H., Sormunen, K.M., Soimasuo, R.M., and Rintala, J.A.,<br />
2002. Screening <strong>of</strong> Physical-Chemical Me<strong>th</strong>ods for Removal <strong>of</strong> Organic Material,<br />
Nitrogen and Toxicity from Low Streng<strong>th</strong> Landfill Le<strong>ac</strong>hates. Chemosphere, 46: 851-858.<br />
Mavinic, D.S., 1998. Le<strong>ac</strong>hate Quality: Effects on Treatability. Proceedings <strong>of</strong> <strong>th</strong>e<br />
International Training Seminar: Management and Treatment <strong>of</strong> MSW Landfill Le<strong>ac</strong>hate,<br />
2-4 December, Venice, Italy.<br />
McBean, E.A., Rovers, F.A., and Farquhar, G.J., 1995. Solid Waste Landfill Engineering<br />
and Design. Prentice-Hall, Inc. New Jersey, USA: ISBN: 0-13-079187-3.<br />
McCann, B., 2002. The Secret <strong>of</strong> Success, Water 21, 8: 42-43.<br />
Mejbri, R., Matejka, G., Lafrance, P., and Mazet, M., 1995. Fr<strong>ac</strong>tioonnement et<br />
Car<strong>ac</strong>terisatioon de la Matiere Organique des Liziviats de Decharges D’ordures Menageres<br />
(Fr<strong>ac</strong>tionation and Char<strong>ac</strong>terization <strong>of</strong> <strong>th</strong>e Organic Matter in Sanitary Landfill Le<strong>ac</strong>hates).<br />
Rev. Sci. de l’Eau, 8: 217-236.<br />
Mendez, R., Lema, J.M., Blazquez, R., Pan, M., and Forjan, C., 1989. Char<strong>ac</strong>terization,<br />
Digestibility and Anaerobic Treatment <strong>of</strong> Le<strong>ac</strong>hates from Old and Young Landfills. Water<br />
Science and <strong>Technology</strong>, 21: 145-155.<br />
Mishra, P.N., Sutton, P.M., and Mourato, D., 1996. Industrial Wastewater Biotreatment<br />
Optimization <strong>th</strong>rough Membrane Applications. Proceedings 89 <strong>th</strong> Mtg. Air and Waste<br />
Management Association, Nashville.<br />
Miskiewicz, T., Oleszkiewicz, J.A., Kosinska, K., Koziarski, S., Kramarz, M., and<br />
Ziobrowski, J., 1982. Dynamic Tests on Yeast Production from Piggery Effluents.<br />
Agriculture Wastes, 4: 3-15.<br />
Morgan, W.S.G., and Villiers, R.H., 1978. Rapid Assessment <strong>of</strong> Water Quality Using<br />
Protozoan Respiratory Responses to Intoxication. Presented at <strong>th</strong>e Biennial conference <strong>of</strong><br />
<strong>th</strong>e <strong>Institute</strong> <strong>of</strong> Water Pollution Control (Sou<strong>th</strong> African Branch).<br />
Morgan, J.W., Froster, C.F., and Evison, L., 1990. A Comparative Study <strong>of</strong> <strong>th</strong>e Nature <strong>of</strong><br />
Biopolymers Extr<strong>ac</strong>ted from Anaerobic and Activated Sludges. Water Research, 24(6):<br />
743-750.<br />
Mukai, T., Takimoto, K., Kono, T., and Okada, M., 2000. Ultrafiltration Behaviour <strong>of</strong><br />
Extr<strong>ac</strong>ellular and Metabolic Products in Activated Sludge System wi<strong>th</strong> UF Separation<br />
Process. Water Research, 34: 902-908.<br />
Muller, E.B., Stou<strong>th</strong>amer, A.H., Vanverseveld H.W., and Eikelboom, D.H., 1995. Aerobic<br />
Domestic Wastewater Treatment in a Pilot Plant wi<strong>th</strong> Complete Sludge Retention by Cross<br />
Flow Filtration. Water Research, 29, 1179-1189.<br />
133
Nagano, A., Arikawa, E., and Kobayashi, H., 1992. The Treatment <strong>of</strong> Liquor Wastewater<br />
Containing High Streng<strong>th</strong> Suspended Solids by Membrane Biore<strong>ac</strong>tor System. Water<br />
Science and <strong>Technology</strong>, 26(3-4): 887-895.<br />
Nagaoka, H., 1999. Nitrogen Removal by Submerged Membrane Separation Activated<br />
Sludge Process. Water Science and <strong>Technology</strong>, 39: 107-114.<br />
Nagaoka, H., Ueda, S., and Miya, A., 1996. Influence <strong>of</strong> B<strong>ac</strong>terial Extr<strong>ac</strong>elluar Polymers<br />
on The Membrane Separation Activated Sludge Process. Water Science and <strong>Technology</strong>,<br />
34:165-172.<br />
Nedwell, D., and Reynolds, P., 1996. Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate by Me<strong>th</strong>anogenic and<br />
Sulphate-Reducing Digestion. Water Research, 30(1): 21-28.<br />
Nielson, P.H., and Jahn, A., 1999. Extr<strong>ac</strong>tion <strong>of</strong> EPS. In: Microbial Extr<strong>ac</strong>ellular<br />
Polymeric Substances. Edited by Wingender, J., Neu, T.R., and Flemming, H.C., Springer,<br />
Berlin, Germany: 49-72.<br />
Nishihara ESRC Ltd., 2001. Technical Details <strong>of</strong> <strong>th</strong>e Yeast Cycle System. Personal<br />
Communication and Company Process Catalog.<br />
Oladimeji, A.A., and Offem, B.O., 1989. Toxicity <strong>of</strong> Lead to Claria lazera, Orechromis<br />
niloticus, Chironomus tentens, and Ben<strong>ac</strong>us sp. Water Air and Soil Pollution, 44: 191-201.<br />
Ortiz, C.P., Steyer, J.P., and Bories, A., 1997. Carbon and Nitrogen Removal from<br />
Wastewater by Candida utilis: Kinetics Aspects and Ma<strong>th</strong>ematical Modelling. Process<br />
Biochemistry, 32(3): 179-189.<br />
Ozturk, I., Altinbas, M., Arikan, O., Tuyluoglu, B.S., and Basturk, A., 1999. Anaerobic<br />
and Chemical Treatability <strong>of</strong> Young Landfill Le<strong>ac</strong>hate. Proceedings <strong>of</strong> 7 <strong>th</strong> International<br />
Waste Management and Landfill Symposium, 4-8 October, Cagliari, Italy: 311-318.<br />
Palit, T., and Qasim, S.R., 1977. Biological Treatment Kinetics <strong>of</strong> Landfill Le<strong>ac</strong>hate.<br />
Journal <strong>of</strong> Environmental Engineering Division, ASCE, 103(EE2): 353-366.<br />
Patterson, W.J., Brezonik, L.P., and Putnam, H.D., 1970. Sludge Activity Parameters and<br />
Their Application to Toxicity Measurements and Activated Sludge. Proceeding 24 <strong>th</strong><br />
Industrial Waste Conference, Indiana, USA.<br />
Peters, T., 1997. Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate by Reverse Osmosis. Proceedings<br />
Sardinia’ 97, 6 <strong>th</strong> International Landfill Symposium, 13-17 October, Cagliari, Italy.<br />
Pirbazari, M., Ravindran, V., Badriyha, B.N., and Kim, S.H., 1996. Hybrid Membrane<br />
Filtration Process for Le<strong>ac</strong>hate Treatment. Water Research, 30(11): 2691-2706.<br />
Pohland, F.G., 1972. Landfill Stabilization wi<strong>th</strong> Le<strong>ac</strong>hate Recycle. Interim Progress<br />
Report, Solid Waste Research Division, U.S.EPA, Ohio, USA.<br />
Pohland, F.G., 1975. Sanitary Landfill Stabilization wi<strong>th</strong> Le<strong>ac</strong>hate Recycle and Residual<br />
Treatment, EPA 600/2-75-043, U.S. EPA, Ohio, USA.<br />
134
Pohland, F.G., and Harper, S.R., 1985. Critical Reviews and Summary <strong>of</strong> Le<strong>ac</strong>hate and<br />
Gas Production from Landfills. EPA Report Number 600/2-86/073.<br />
Pohland, F.G., Stratakis, M., Cross, W.H., and Tyahla, S.F., 1990. Controlled Landfill<br />
Management <strong>of</strong> Municipal Solid Waste and Hazardous Wastes. Proceedings <strong>of</strong> 1990<br />
WPCF National Specialty Conference on Water Quality Management <strong>of</strong> Landfills, 15-18<br />
July, Illinois, USA: 3-16 – 3-32.<br />
Pohland, F.G., and Kim, J.C., 1999. In Situ Anaerobic Treatment <strong>of</strong> Le<strong>ac</strong>hate in Landfill<br />
Biore<strong>ac</strong>tors. Water Science and <strong>Technology</strong>, 40(8): 203 -210.<br />
Pollution Control Department, 2000. Research and Development <strong>of</strong> Landfill Le<strong>ac</strong>hate<br />
Treatment. Ministry <strong>of</strong> Science, <strong>Technology</strong> and Environment. Bangkok, Thailand: ISBN:<br />
9-74-787938-7.<br />
Pouet, M.F., and Grasmicj, A., 1995. Micr<strong>of</strong>iltration <strong>of</strong> Urban Wastewater: <strong>th</strong>e Roles <strong>of</strong><br />
<strong>th</strong>e Different Organic Fr<strong>ac</strong>tions in Fouling <strong>th</strong>e Membrane. Proceeding Euromembrane’95,<br />
University <strong>of</strong> Ba<strong>th</strong>, England: 482-486.<br />
Praet, E., Jupsin, H., El Mossaoui, M., Rouxhet, V., and Vasel, J.L., 2001. Use <strong>of</strong> a<br />
Membrane Biore<strong>ac</strong>tor and an Activated Carbon Adsorber for <strong>th</strong>e Treatment <strong>of</strong> MSW<br />
Landfill Le<strong>ac</strong>hates, Proceedings Sardinia’01, 8 <strong>th</strong> International Waste Management and<br />
Landfill Symposium, Cagliari, Italy.<br />
Qasim, S.R., and Chiang, W., 1994. Sanitary Landfill Le<strong>ac</strong>hate- Generation, Control and<br />
Treatment. Technomic Publishing Co., Inc. Pennsylvania, USA: ISBN: 1-56-676129-8.<br />
Ragle N., Kissel, J.C., Onger<strong>th</strong>, J.E., and DeWalle F.B., 1995. Composition and Variability<br />
<strong>of</strong> Le<strong>ac</strong>hate from Recent and Aged Areas wi<strong>th</strong>in a Municipal Landfill. Water Environment<br />
Research, 67(2):238-243, 1995.<br />
Raina, S., and Malvinic, D.S., 1985. Comparison <strong>of</strong> Fill and Draw Re<strong>ac</strong>tors for Treatment<br />
<strong>of</strong> Landfill Le<strong>ac</strong>hate. Water Pollution Research Journal, <strong>of</strong> Canada, 20(2): 12-28.<br />
Rautenb<strong>ac</strong>h R., and Albrecht, R., 1989. Membrane Processes, John Wiley and Sons Ltd.:<br />
ISBN: 0-47-191110-0.<br />
Rautenb<strong>ac</strong>h, R., and Mellis, R., 1994. Wastewater Treatment by a Combination <strong>of</strong><br />
Biore<strong>ac</strong>tor and Nan<strong>of</strong>iltration. Desalination, 95: 171-188.<br />
Reeves, T.G., 1972. Nitrogen Removal: A Literature Review. Journal <strong>of</strong> Water Pollution<br />
Control Federation, 44(10): 1895-1908.<br />
Reeves, J.B., 1976. Activated Sludge System Influent Toxicity Monitoring <strong>th</strong>rough<br />
Utilization <strong>of</strong> Commercial, Continuous Respirometer. N.S. Dissertation, Virginia<br />
Polytechnic <strong>Institute</strong> and State University, USA.<br />
Robinson, H.D., and Gran<strong>th</strong>am, G., 1988. The Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hates in On-site<br />
Aerated Lagoon Plants: Experience in Britain and Ireland. Water Research, 22(6): 733-<br />
747.<br />
135
Robinson, H.D., and Luo, M.M.H., 1991. Char<strong>ac</strong>terization and Treatment <strong>of</strong> Landfill<br />
Le<strong>ac</strong>hates from Hong Kong Landfill Sites. Journal <strong>of</strong> <strong>Institute</strong> Water and Environmental<br />
Management, 5: 326-335.<br />
Robinson, H.D., Barr, M.J., and Last, S.D., 1992. Le<strong>ac</strong>hate Collection, Treatment and<br />
Disposal. Journal <strong>of</strong> <strong>Institute</strong> Water and Environmental Management, 6: 321-332.<br />
Robinson, H.D., and Maris, P.J., 1983. The Treatment <strong>of</strong> Le<strong>ac</strong>hates from Domestic Wastes<br />
in Landfills–I: Aerobic Biological Treatment <strong>of</strong> Medium-Streng<strong>th</strong> Le<strong>ac</strong>hate. Water<br />
Research, 17(11): 1537-1548<br />
Robinson, H.D., and Maris, P.J., 1985. The Treatment <strong>of</strong> Le<strong>ac</strong>hates from Domestic Waste<br />
in Landfill Sites, Journal <strong>of</strong> Water Pollution Control Federation, 57(1): 30-38.<br />
Robinson, H.D., 1999. State <strong>of</strong> <strong>th</strong>e Art Landfill Le<strong>ac</strong>hate Treatment Systems in <strong>th</strong>e UK and<br />
Ireland. Waste Science and Research, England.<br />
Rodney, F.B., 1993. Modern Experimental Biochemistry. 2 nd Edition, USA:<br />
Benjamin/Cummings Pub. Co.: ISBN: 0-80-530545-9.<br />
Rosenberg, S., Kraume, M., and Szewzyk, U., 1999. Operation <strong>of</strong> Different Membrane<br />
Biore<strong>ac</strong>tors: Experimental Results and Physiological State <strong>of</strong> <strong>th</strong>e Microorganisms.<br />
Proceedings Membrane <strong>Technology</strong> in Environmental Management, Tokyo, Japan: 310-<br />
316.<br />
Sanin, D., and Vsilind. P.A., 2000. Bi<strong>of</strong>locculation <strong>of</strong> Activated Sludge: The Role <strong>of</strong><br />
Calcium Ions and Extr<strong>ac</strong>ellular Polymers. Environmental <strong>Technology</strong>, 21: 1405-1412.<br />
Sato, T., and Ishii, Y., 1991. Effects <strong>of</strong> Activated Sludge Properties on Water Flux <strong>of</strong><br />
Ultration Membrane Used for Human Excrement Treatment. Water Science and<br />
<strong>Technology</strong>, 23: 1601-1608.<br />
Sawyer, C.N., McCarty, P.L., and Parkin, G.F., 1994. Chemistry for Environmental<br />
Engineering. McGraw-Hill, USA: ISBN: 0-07-113908-7.<br />
Schrab, G.E., Brown, K.W., and Donnelly, K.C., 1993. Acute and Genetic Toxicity <strong>of</strong><br />
Municipal Landfill Le<strong>ac</strong>hate. Water Air and Soil Pollution, 69: 99-112.<br />
Schuk, W.W., and James, S.C., 1986. Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate at Publicly Owned<br />
Treatment Works. Waste Management and research, 4: 265-277.<br />
Scioli, C., and Vollaro, L., 1997. Use <strong>of</strong> Yarrowia lipolytica to Reduce Pollution in Olive<br />
Mill Wastewaters. Water Research, 31(10): 2520–2524.<br />
Scott, J.A., and Smi<strong>th</strong>, K.L., 1997. A Biore<strong>ac</strong>tor Coupled to a Membrane to Provide<br />
Aeration and Filtration in Ice-Cream F<strong>ac</strong>tory Wastewater Remediation. Water Research,<br />
31(1): 69-74.<br />
136
Shin, H.S., An, H., Kang, S.T., Choi, K.H., and Jun, K.S., 1999. Fouling Char<strong>ac</strong>teristics in<br />
Pilot Scale Submerged Membrane Biore<strong>ac</strong>tor. Proceeding 1 st WEFTEC’ 99, New Orleans,<br />
USA.<br />
Siegrist, H., Rei<strong>th</strong>aar, S., and Lais, P., 1998. Nitrogen Loss in a Nitrifying Rotating<br />
Cont<strong>ac</strong>tor Treating Ammonium Rich Le<strong>ac</strong>hate wi<strong>th</strong>out Organic Carbon. Water Science<br />
and <strong>Technology</strong>, 37(4-5): 589–591.<br />
Sivapornpun, V., 2000. Heavy Metals in Landfill Le<strong>ac</strong>hate: Options for Reduction and<br />
Treatment. Master <strong>Thesis</strong>, <strong>Asian</strong> <strong>Institute</strong> <strong>of</strong> <strong>Technology</strong>, Thailand.<br />
Slater, C.S., Uchrin, C.G., and Ahlert, R.C., 1985. Ultrafiltration Processes for <strong>th</strong>e<br />
Char<strong>ac</strong>terization and Separation <strong>of</strong> Landfill Le<strong>ac</strong>hate. Journal <strong>of</strong> Environmental science<br />
Heal<strong>th</strong>, A20(1): 97-111.<br />
Smi<strong>th</strong>, P.G., and Arab, F.K., 1988. The Role <strong>of</strong> Air Bubbles in <strong>th</strong>e Desorption <strong>of</strong> Ammonia<br />
from Landfill Le<strong>ac</strong>hates in High pH Aerated Lagoon. Water, Air and Soil Pollution, 38:<br />
333-343.<br />
Solyom, P., 1977. Industrial Experiences wi<strong>th</strong> Toxiguard, a Toxicity Monitoring System.<br />
Prog. Water <strong>Technology</strong>, 9: 193-198.<br />
Solyom, P., Boman, B., and Bjorndal, H., 1976. Continuous Monitoring <strong>of</strong> Acute-Toxic<br />
Substances in Wastewater. Prog. Water <strong>Technology</strong>, 8: 417-422.<br />
Srina<strong>th</strong>, E.G., and Loehr, R.C., 1974. Ammonia Desorption by Diffused Aeration. Journal<br />
<strong>of</strong> Water Pollution Control Federation, 46(8): 1939-1957.<br />
Steensen, M., 1993. Removal <strong>of</strong> Non-biodegradable Organics from Le<strong>ac</strong>hate by Chemical<br />
Oxidation. Proceedingd Sardina’ 93, 4 <strong>th</strong> International Landfill Symposium, Cagliari, Italy:<br />
945-958.<br />
Steensen, M., 1997. Chemical Oxidation for <strong>th</strong>e Treatment <strong>of</strong> Le<strong>ac</strong>hate-Process<br />
Comparison and Results from Full-Scale Plants. Water Science and <strong>Technology</strong>, 35(4):<br />
249-256.<br />
Stephenson, T., Judd, S., Jefferson, B., and Brindle, K., 2000. Membrane Biore<strong>ac</strong>tors for<br />
Wastewater Treatment. IWA Publishing: ISBN: 1-90-022207-8.<br />
Str<strong>ac</strong>han, L.J., Trois, C., Robinson, H.D., and Olufsen, J.S., 2000. Appropriate Biological<br />
Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hate wi<strong>th</strong> Full Nitrification and Denitrification. Conference<br />
Proceedings, WISA 2000, Sun City, Sou<strong>th</strong> Africa.<br />
Suflita, J.M., Gerba, C.P., Ham, R.K., Palmisano, A.C., Ra<strong>th</strong>je, W.L., and Robinson, J.A.,<br />
1992. The World’s Largest Landfill: Multidisciplinary Investigation. Environmental<br />
Science <strong>Technology</strong>, 26: 1486-1494.<br />
Sun, D.D., Zeng, J.L., and Tay, J.H., 2002. A Submerged Tubular Ceramic Membrane<br />
Biore<strong>ac</strong>tor for High Streng<strong>th</strong> Wastewater Treatment. Water Science and <strong>Technology</strong>,<br />
47(1): 105-111.<br />
137
Talinli, I., and Tokta, S., 1994. Oxygen Uptake Rate Inhibition Test: A Modified Me<strong>th</strong>od<br />
for Priority Pollutants. Environmental <strong>Technology</strong>, 15: 979-988.<br />
Tatsi, A.A., and Zouboulis, A.I., 2002. A field investigation <strong>of</strong> <strong>th</strong>e quantity and quality <strong>of</strong><br />
le<strong>ac</strong>hate from a municipal solid waste landfill in a Mediterranean climate (Thessaloniki,<br />
Greece). Advances in Environmental Research, 6: 207-219.<br />
Tchobanoglous, G., Burton, F.L., and Stensel, H.D., 2003. Wastewater Engineering:<br />
Treatment and Reuse. 4 <strong>th</strong> Edition, McGraw-Hill, USA: ISBN: 0-07-112250-8.<br />
Temmink, H., Vanrolleghem, P., Klapwijk, A., and Verstraete, W., 1993. Biological Early<br />
Warning Systems for Toxicity Based on Activated Sludge Respirometry, Water Science<br />
and <strong>Technology</strong>, 28(11-12): 415-425.<br />
Thurman, E.M., and Malcolm, R.L., 1981. Preparative Isolation <strong>of</strong> Aquatic Substances.<br />
Environmental Science and <strong>Technology</strong>, 15: 463-466.<br />
Timur, H., and Ozturk, I., 1999. Anaerobic Sequencing Batch Re<strong>ac</strong>tor Treatment <strong>of</strong><br />
Landfill Le<strong>ac</strong>hate. Water Research, 33(15): 3225-3230.<br />
Trankler, J., Manandhari, D.R., Xiaoning, Q., Sivapornpun, V., and Scholl, W., 2001.<br />
Effects <strong>of</strong> Monsooning Conditions on <strong>th</strong>e Management <strong>of</strong> Landfill Le<strong>ac</strong>hate in Tropical<br />
Countries. Proceedingd Sardina’ 01, 8 <strong>th</strong> International Waste Management and Landfill<br />
Symposium, Cagliari, Italy: 59-68.<br />
Tsai, C.T., Lin, S.T., Shue, Y.C., and Su, P.L., 1997. Electrolysis <strong>of</strong> Solution Organic<br />
Matter in Le<strong>ac</strong>hate from Landfills. Water Research, 31(12): 3073-3081.<br />
Turk, O., and Mavinic, D.S., 1989. Maintaining Nitrite Build-Up in a System Acclimatized<br />
to Free Ammonia, Water Research, 23 (11): 1383-1388.<br />
Ueda, T., Hata, K., and Kikuoka, Y., 1996. Treatment <strong>of</strong> Domestic Sewage from Rural<br />
Settlements by a Membrane Biore<strong>ac</strong>tor. Water Science and <strong>Technology</strong>, 34: 189-196.<br />
Ulo<strong>th</strong>, V.C., and Mavinic, D.S., 1977. Aerobic Biotreatment <strong>of</strong> High Streng<strong>th</strong> Le<strong>ac</strong>hate.<br />
Journal <strong>of</strong> <strong>th</strong>e Environmental Engineering Division, ASCE, 103(EE6): 647-661.<br />
Vanrolleghem, P.A., Spanjers, H., Petersen, B., Ginestet, P., and Tak<strong>ac</strong>s, I., 1999.<br />
Estimating (combination <strong>of</strong>) <strong>ac</strong>tivated Sludge Model No. 1 Parameters and Components by<br />
Respirometry. Water Science and technology, 39(1): 195-214.<br />
Venkatadri, R., and Peters, R.W., 1993. Chemical Oxidation Technologies: Ultraviolet<br />
Light/Hydrogenperoxide, Fenton’s Reagent and Titanium Dioxide-Assisted Photocatalysis.<br />
Hazardrous Waste and Hazardrous Materials, 10(2): 107-149.<br />
Vicevic, G.P.., Top, P.J., and Laughlin, R.G.W., 1992. Aerobic and Anaerobic Fixed Film<br />
Biological Re<strong>ac</strong>tors. In: Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by Christensen, T.H., Cossu,<br />
R., and Stegmann, R. Elsevier Science Publishers Ltd., England: ISBN: 1-85-166733-4:<br />
229-243.<br />
138
Visvana<strong>th</strong>an, C., Ben Aim, R., and Parameshwaran, K., 2000. Membrane Separation<br />
Biore<strong>ac</strong>tors for Wastewater Treatment. Environmental Science and <strong>Technology</strong>, 30(1): 1-<br />
48.<br />
Visvana<strong>th</strong>an, C., Trankler, J., Kuruparan, P., and Xiaoning, Q., 2003. Effects <strong>of</strong><br />
Monsooning Conditions on <strong>th</strong>e Generation and Composition <strong>of</strong> Landfill Le<strong>ac</strong>hate-<br />
Lysimeter Experiments wi<strong>th</strong> Various Input and Design Features. Proceeding Sardinia’03,<br />
9 <strong>th</strong> International Waste Management and Landfill Symposium, Cagliari, Italy.<br />
Webber, W.J., and Smi<strong>th</strong>, E.H., 1986. Removing Dissolved Organic Contaminants from<br />
Water. Environmental Science and <strong>Technology</strong>, 20(10): 970-979.<br />
Weber, B., and Holz, F., 1992. Combination <strong>of</strong> Activated Sludge Pre-treatment and<br />
Reverse Osmosis. In: Landfill <strong>of</strong> Waste: Le<strong>ac</strong>hate. Edited by Christensen, T.H., Cossu, R.,<br />
and Stegmann, R. Elsevier Science Publishers Ltd., England: ISBN: 1-85-166733-4: 323-<br />
332.<br />
Welander, U., Henrysson, T., and Welander, T., 1998. Biological Nitrogen Removal from<br />
Municipal Landfill Le<strong>ac</strong>hate in Pilot Scale Suspended Carrier Bi<strong>of</strong>ilm Process. Water<br />
Research, 32(5): 1564-1570.<br />
Wisniewski, C., and Grasmick, A., 1998. Floc Size Distribution in a Membrane Biore<strong>ac</strong>tor<br />
and Consequences for Membrane Fouling. Colloids and Surf<strong>ac</strong>es A, 138: 403-411.<br />
Wisniewski, C., Grasmick, A., and Cruz, A.L., 2000. Critical Particle Size in Membrane<br />
Biore<strong>ac</strong>tor Case <strong>of</strong> a Denitirifying B<strong>ac</strong>terial Suspension. Journal <strong>of</strong> Membrane Science,<br />
178: 141-150.<br />
Wong, P.T., and Mavinic, D.S., 1984. Treatment <strong>of</strong> a Municipal Le<strong>ac</strong>hate under Multi-<br />
Variable Conditions. Journal <strong>of</strong> Water Pollution Control Federation, Research, Canada.<br />
Wu, Y.C., Hao, O.J., Ou. K.C., and Scholze, R.J., 1988. Treatment <strong>of</strong> Le<strong>ac</strong>hate from a<br />
Solid Waste Landfill Site Using a Two-Stage Anaerobic Filter. Biotechnology and<br />
Bioengineering, 31: 257-266.<br />
Yalmaz, G., and Öztürk, I., 2001. Biological Ammonia Removal from Anaerobically Pretreated<br />
Landfill Le<strong>ac</strong>hate in Sequencing Batch Re<strong>ac</strong>tors (SBR). Water Science and<br />
<strong>Technology</strong>, 43 (3): 307-314<br />
Yamamoto, K., Hissa, M., Mahmood, T., and Matsuo, T., 1989. Direct Solid Liquid<br />
Separation Using Hollow Fiber Membrane in an Activated Sludge Aeration Tank. Water<br />
Science and <strong>Technology</strong>, 21: 43-54.<br />
Yangin, C., Yilmaz, S., Altinbas, M., and Ozturk, I., 2002. A New Process for <strong>th</strong>e<br />
Combined Treatment <strong>of</strong> Municipal Wastewaters and Landfill Le<strong>ac</strong>hates in Coastal Areas.<br />
Water Science and <strong>Technology</strong>, 46(8): 111-118.<br />
Yoon, J., Cho, S., Cho, Y., and Kim, S., 1998. The Char<strong>ac</strong>teristics <strong>of</strong> Coagulation <strong>of</strong><br />
Fenton Re<strong>ac</strong>tion in <strong>th</strong>e Removal <strong>of</strong> Landfill Le<strong>ac</strong>hate Organics. Water Science and<br />
<strong>Technology</strong>, 38(2): 209-214.<br />
139
Zaloum, R., and Abbott, M., 1997. Anaerobic Pretreatment Improves Single Sequencing<br />
Batch Re<strong>ac</strong>tor Treatment <strong>of</strong> Landfill Le<strong>ac</strong>hates. Water Science and <strong>Technology</strong>, 35(1),<br />
207-214.<br />
Zapf-Gilje, R., and Mavinic, D.S., 1981. Temperature Effects on Biostabilization <strong>of</strong><br />
Le<strong>ac</strong>hate. Journal <strong>of</strong> <strong>th</strong>e Environmental Engineering Division, ASCE, 107(EE4): 653-663.<br />
140
Appendix A<br />
Pictures <strong>of</strong> Experiments<br />
141
142<br />
Figure A-1 YMBR and BMBR Re<strong>ac</strong>tors
Raw Le<strong>ac</strong>hate YMBR Effluent BMBR Effluent<br />
Figure A-2 Color Comparison <strong>of</strong> Raw Le<strong>ac</strong>hate wi<strong>th</strong> Selected Water after Treatment<br />
(MBR System)<br />
Figure A-3 Color Comparison <strong>of</strong> Raw Le<strong>ac</strong>hate wi<strong>th</strong> Selected Water after Treatment<br />
(Coupling Ammonia Stripping wi<strong>th</strong> MBR System)<br />
143
New New Membrane<br />
Membrane<br />
After After Long-run<br />
Long-run<br />
After After Chemical<br />
Chemical<br />
Cleaning<br />
After Long-run (BMBR)<br />
Cleaning<br />
After Long-run (BMBR)<br />
Cleaning<br />
After After Washing<br />
Washing<br />
(YMBR)<br />
(YMBR)<br />
wi<strong>th</strong> wi<strong>th</strong> Tap Tap Water<br />
Water<br />
Figure A-4 Char<strong>ac</strong>teristics <strong>of</strong> Membrane<br />
144
Appendix B<br />
Le<strong>ac</strong>hate Char<strong>ac</strong>teristics and<br />
Experimental Data <strong>of</strong> Acclimation<br />
145
Table B-1 Le<strong>ac</strong>hate Char<strong>ac</strong>teristic <strong>of</strong> <strong>th</strong>e Primary Sources and <strong>th</strong>e Feed<br />
Pa<strong>th</strong>um<strong>th</strong>ani Landfill Site Ram-Indra Transfer Station Feed<br />
Sample No. NH4 + -N TKN COD NH4<br />
(mg/L) (mg/L) (mg/L)<br />
+ -N TKN COD NH4<br />
(mg/L) (mg/L) (mg/L)<br />
+ -N TKN COD<br />
(mg/L) (mg/L) (mg/L)<br />
1 2,184 2,349 5,410 349 1,292 87,200 1,831 2,013 7,412<br />
2 1,820 1,968 3,660 333 1,247 85,020 1,537 1,719 7,521<br />
3 1,691 1,882 4,230 319 1,652 73,840 1,562 1,848 7,692<br />
4 1,691 1,882 4,100 336 1,249 32,190 1,604 1,893 8,195<br />
5 1,781 2,050 3,940 448 1,361 34,280 1,669 1,957 7,200<br />
6 1,756 2,019 4,170 333 1,226 33,330 1,753 1,982 7,000<br />
7 1,607 1,884 3,288 409 921 31,151 1,417 1,750 7,233<br />
8 1,719 2,044 3,243 434 879 32,432 1,442 1,764 7,135<br />
146
Table B-2 Acclimation <strong>of</strong> Mixed Yeast Sludge to Landfill Le<strong>ac</strong>hate Containing High<br />
Organic and Ammonia Concentration<br />
Time<br />
COD (mg/L) COD Removal MLSS F/M ratio<br />
(days) Influent Effluent (%) (mg/L) (d -1 )<br />
1 3,800 2,090 45 3,750 1.01<br />
3 3,800 1,710 55 3,933 0.97<br />
6 4,000 1,440 64 4,233 0.94<br />
9 4,000 1,320 67 4,533 0.88<br />
12 4,150 1,287 69 4,800 0.86<br />
14 4,150 1,245 70 5,367 0.77<br />
17 4,320 1,210 72 5,633 0.77<br />
21 4,320 1,166 73 6,240 0.69<br />
25 4,800 1,296 73 6,560 0.73<br />
29 4,800 1,248 74 6,740 0.71<br />
35 4,800 1,200 75 7,040 0.68<br />
39 5,530 1,438 74 7,540 0.73<br />
42 5,530 1,327 76 8,167 0.68<br />
44 5,,530 1,272 77 8,667 0.64<br />
46 6,105 1,526 75 9,800 0.62<br />
50 6,105 1,404 77 10,450 0.58<br />
52 7,071 1,697 76 10,750 0.66<br />
54 7,071 1,838 74 11,240 0.63<br />
56 7,300 1,898 74 11,400 0.64<br />
58 7,300 1,825 75 11,950 0.61<br />
61 7,300 1,898 74 11,850 0.62<br />
67 7,300 1,825 75 11,700 0.62<br />
147
Table B-3 Acclimation <strong>of</strong> Mixed B<strong>ac</strong>teria Sludge to Landfill Le<strong>ac</strong>hate Containing High<br />
Organic and Ammonia Concentration<br />
Time<br />
COD (mg/L) COD Removal MLSS F/M ratio<br />
(days) Influent Effluent (%) (mg/L) (d -1 )<br />
1 3,800 2,014 47 2,620 1.45<br />
3 3,800 1,786 53 2,667 1.42<br />
6 4,000 1,640 59 2,860 1.40<br />
9 4,000 1,600 60 3,060 1.31<br />
12 4,150 1,577 62 3,300 1.26<br />
14 4,150 1,577 62 3,740 1.11<br />
17 4,320 1,555 64 3,880 1.11<br />
21 4,320 1,469 66 4,233 1.02<br />
25 4,800 1,632 66 4,467 1.07<br />
29 4,800 1,632 66 4,833 0.99<br />
35 4,800 1,680 65 5,150 0.93<br />
39 5,530 1,880 66 5,260 1.05<br />
42 5,530 1,880 66 5,367 1.03<br />
44 5,530 1,825 67 5,480 1.01<br />
46 6,105 2,076 66 5,733 1.06<br />
50 6,105 2,198 64 6,260 0.98<br />
52 7,071 2,616 63 6,380 1.11<br />
54 7,071 2,475 65 6,360 1.11<br />
56 7,300 2,628 64 6,340 1.15<br />
58 7,300 2,482 66 6,380 1.14<br />
61 7,300 2,555 65 6,380 1.14<br />
67 7,300 2,482 66 6,420 1.14<br />
148
Appendix C<br />
Experimental Data <strong>of</strong> Biokinetic Study and Toxicity Study<br />
149
C.1 OUR Determination<br />
In <strong>th</strong>is study a selected volume <strong>of</strong> wastewater <strong>of</strong> known total COD is mixed wi<strong>th</strong> a<br />
selected volume <strong>of</strong> mixed liquor <strong>of</strong> known MLVSS concentration in a batch re<strong>ac</strong>tor. After<br />
mixing, <strong>th</strong>e OUR is measured approximately every 5 to 10 minutes until OUR attains to a<br />
constant value <strong>th</strong>at is approximate or equal to OUR in <strong>th</strong>e endogenous phase (Ekama, et al.,<br />
1986). The respirogram is obtained by plotting <strong>th</strong>e curve <strong>of</strong> OUR versus time as shown in<br />
Figure C-1.<br />
Where<br />
OUR (mg/L.h)<br />
D<br />
A<br />
g<br />
g<br />
B<br />
C<br />
Time (min)<br />
Figure C-1 OUR Response in Respirometer (Ekama, et al., 1986)<br />
Area A: This area gives <strong>th</strong>e concentration <strong>of</strong> readily biodegradable COD<br />
oxidized by <strong>th</strong>e biomass.<br />
Area B: This area represents <strong>th</strong>e amount <strong>of</strong> less readily biodegradable<br />
material being oxidized.<br />
Area C: This area shows <strong>th</strong>e amount <strong>of</strong> oxygen being used to convert<br />
ammonia into oxidized nitrate (nitrification).<br />
Area D: The area under <strong>th</strong>e whole curve shows <strong>th</strong>e total oxygen demand <strong>of</strong><br />
<strong>th</strong>e liquor. This is <strong>th</strong>e total amount <strong>of</strong> oxygen which must be<br />
supplied to <strong>th</strong>e sludge to <strong>ac</strong>hieve full treatment.<br />
OUR at line e: The respiration rate at <strong>th</strong>e end <strong>of</strong> <strong>th</strong>e curve is <strong>th</strong>e endogenous<br />
respiration rate. This rate is proportional to <strong>th</strong>e <strong>ac</strong>tivity <strong>of</strong> <strong>th</strong>e<br />
biomass.<br />
OUR at line f: This rate is <strong>th</strong>e average respiration rate for <strong>th</strong>e period where<br />
nitrification and <strong>th</strong>e breakdown <strong>of</strong> less readily biodegradable<br />
substrates are occurring.<br />
150<br />
f<br />
T<br />
e<br />
e
y:<br />
Where:<br />
OUR at line g: This is <strong>th</strong>e maximum respiration rate observed at <strong>th</strong>e start-up <strong>of</strong> <strong>th</strong>e<br />
respiration cycles. At <strong>th</strong>is point all oxidative re<strong>ac</strong>tions take pl<strong>ac</strong>e,<br />
including <strong>th</strong>e oxidation <strong>of</strong> carbon and nitrogen.<br />
Time T: The time for <strong>th</strong>e sample to re<strong>ac</strong>h an endogenous respiration rate.<br />
Specific OUR <strong>of</strong> substrate oxidation at a substrate concentration S (OURx,ox) is given<br />
OUR X , ox OURX<br />
, t − OURX<br />
, e<br />
= (C-1)<br />
OURx,t = Total respiration rate (mg O2/mg VSS.h)<br />
OURx,e = Endogenous respiration rate (mg O2/mg VSS .h)<br />
Fur<strong>th</strong>er specific substrate removal rate at a substrate concentration S (RX) is given by:<br />
OURX<br />
, ox<br />
RX<br />
=<br />
OC / S<br />
(C-2)<br />
Where<br />
RX = Substrate removal rate (mg COD removed/mg VSS.h)<br />
OC = Net oxygen consumption (mg O2/L)<br />
S = Substrate concentration (mg COD/L)<br />
OC is <strong>th</strong>en equal to <strong>th</strong>e area between <strong>th</strong>e OUR curve and <strong>th</strong>e second plateau level<br />
where <strong>th</strong>e OUR decreases rapidly and levels <strong>of</strong>f (OC = Area A+area B) (Figure C-1)<br />
Biomass yield coefficient (Y) is expressed as:<br />
1 ⎛ OC ⎞<br />
Y = ⎜1−<br />
⎟<br />
f ⎝ S ⎠<br />
and <strong>th</strong>e specific grow<strong>th</strong> rate (µ ) as:<br />
(C-3)<br />
µ = Y. R<br />
(C-4)<br />
X<br />
Where<br />
µ = Specific grow<strong>th</strong> rate (h -1 )<br />
f = COD/VSS ratio <strong>of</strong> <strong>th</strong>e sludge (mg COD/mg VSS)<br />
Y = Yield coefficient (mg VSS/mg COD removed)<br />
151
Table C-1 Biokinetic Experimental Data <strong>of</strong> Mixed B<strong>ac</strong>terial Sludge wi<strong>th</strong> Le<strong>ac</strong>hate<br />
S<br />
(mg COD/L)<br />
OURx,t<br />
(mg O2/mg VSS. h)<br />
OURx,e<br />
(mg O2/mg VSS. h)<br />
152<br />
OC<br />
(mg O2/L)<br />
OURx,ox<br />
(mg O2/mg VSS. h)<br />
OC/S<br />
rx<br />
(mg COD/mg VSS. h)<br />
Yvss<br />
(mg VSS/mg COD)<br />
7.0 0.0080 0.0036 3.3 0.0044 0.47 0.0093 0.39 0.09<br />
14.0 0.0084 0.0039 3.4 0.0045 0.24 0.0185 0.56 0.25<br />
21.0 0.0082 0.0036 3.8 0.0047 0.18 0.0259 0.60 0.38<br />
42.0 0.0123 0.0042 10.7 0.0081 0.25 0.0318 0.55 0.42<br />
Table C-2 Biokinetic Experimental Data <strong>of</strong> Mixed Yeast Sludge wi<strong>th</strong> Le<strong>ac</strong>hate<br />
S<br />
(mg COD/L)<br />
OURx,t<br />
(mg O2/mg VSS. h)<br />
OURx,e<br />
(mg O2/mg VSS. h)<br />
OC<br />
(mg O2/L)<br />
OURx,ox<br />
(mg O2/mg VSS. h)<br />
OC/S<br />
rx<br />
(mg COD/mg VSS. h)<br />
Yvss<br />
(mg VSS/mg COD)<br />
5.6 0.0031 0.0008 1.62 0.0023 0.29 0.0080 0.50 0.09<br />
11.2 0.0040 0.0011 3.40 0.0029 0.30 0.0096 0.49 0.11<br />
16.8 0.0052 0.0012 5.04 0.0040 0.30 0.0133 0.49 0.16<br />
28.0 0.0097 0.0016 10.40 0.0081 0.37 0.0218 0.44 0.23<br />
40.8 0.0067 0.0008 10.87 0.0059 0.27 0.0221 0.51 0.27<br />
µ<br />
(day -1 )<br />
µ<br />
(day -1 )
Table C-3 Experimental Results for Ammonia Toxicity in Mixed B<strong>ac</strong>terial Sludge at COD Concentration <strong>of</strong> 7.0 mg/L<br />
NH4Cl<br />
(mg NH4-N/L)<br />
OURx,t<br />
(mg O2/mg VSS. h)<br />
OURx,e<br />
(mg O2/mg VSS. h)<br />
153<br />
OC<br />
(mg O2/L)<br />
OURx,ox<br />
(mg O2/mg VSS. h)<br />
OC/S<br />
rx<br />
(mg COD/mg VSS. h)<br />
Yvss<br />
(mg VSS/mg COD)<br />
70 0.0078 0.0031 3.30 0.0047 0.47 0.0100 0.39 0.09<br />
1000 0.0062 0.0033 3.38 0.0029 0.48 0.0060 0.38 0.05<br />
1500 0.0066 0.0038 3.64 0.0028 0.52 0.0054 0.35 0.05<br />
2000 0.0061 0.0034 4.23 0.0027 0.60 0.0045 0.29 0.03<br />
Table C-4 Experimental Results for Ammonia Toxicity in Mixed Yeast Sludge at COD Concentration <strong>of</strong> 5.6 mg/L<br />
NH4Cl<br />
(mg NH4-N/L)<br />
OURx,t<br />
(mg O2/mg VSS. h)<br />
OURx,e<br />
(mg O2/mg VSS. h)<br />
OC<br />
(mg O2/L)<br />
OURx,ox<br />
(mg O2/mg VSS. h)<br />
OC/S<br />
rx<br />
(mg COD/mg VSS. h)<br />
Yvss<br />
(mg VSS/mg COD)<br />
70 0.0031 0.0008 1.62 0.0023 0.29 0.0080 0.50 0.09<br />
1000 0.0031 0.0009 1.67 0.00225 0.30 0.0075 0.49 0.09<br />
1500 0.0030 0.0007 1.72 0.0023 0.31 0.0075 0.48 0.09<br />
2000 0.0031 0.0008 1.68 0.0023 0.30 0.0077 0.49 0.09<br />
µ<br />
(day -1 )<br />
µ<br />
(day -1 )
Table C-5 Experimental Results for Lead Toxicity <strong>of</strong> Mixed B<strong>ac</strong>teria Sludge at COD Concentration <strong>of</strong> 7.0 mg/L<br />
Pb(NO3)2<br />
(mg/L)<br />
OURx,t<br />
(mg O2/mg VSS. h)<br />
OURx,e<br />
(mg O2/mg VSS. h)<br />
154<br />
OC<br />
(mg O2/L)<br />
OURx,ox<br />
(mg O2/mg VSS. h)<br />
OC/S<br />
rx<br />
(mg COD/mg VSS. h)<br />
Yvss<br />
(mg VSS/mg COD)<br />
0 0.0078 0.0031 3.30 0.0047 0.47 0.0100 0.39 0.09<br />
20 0.0061 0.0038 2.77 0.0023 0.40 0.0058 0.44 0.06<br />
50 0.0051 0.0038 2.22 0.0013 0.32 0.0041 0.50 0.05<br />
70 0.0042 0.0036 1.65 0.0006 0.24 0.0025 0.56 0.03<br />
100 0.0032 0.0031 0.95 0.0001 0.14 0.0007 0.64 0.01<br />
Table C-6 Experimental Results for Lead Toxicity <strong>of</strong> Mixed Yeast Sludge at COD Concentration <strong>of</strong> 5.6 mg/L<br />
Pb(NO3)2<br />
(mg/L)<br />
OURx,t<br />
(mg O2/mg VSS. h)<br />
OURx,e<br />
(mg O2/mg VSS. h)<br />
OC<br />
(mg O2/L)<br />
OURx,ox<br />
(mg O2/mg VSS. h)<br />
OC/S<br />
rx<br />
(mg COD/mg VSS. h)<br />
Yvss<br />
(mg VSS/mg COD)<br />
0.0 0.0031 0.0008 1.62 0.0023 0.29 0.0080 0.50 0.09<br />
2.5 0.0022 0.0007 1.32 0.0015 0.24 0.0064 0.53 0.08<br />
5.0 0.0023 0.0012 1.31 0.0011 0.23 0.0047 0.54 0.06<br />
15.0 0.0017 0.0009 1.33 0.0008 0.24 0.0034 0.53 0.04<br />
25.0 0.0013 0.0010 2.68 0.0003 0.48 0.0006 0.36 0.01<br />
µ<br />
(day -1 )<br />
µ<br />
(day -1 )
Appendix D<br />
Membrane Resistance Studies<br />
155
Table D-1 Experimental Data for Determination <strong>of</strong> Initial Membrane Resistance <strong>of</strong><br />
BMBR Membrane (A = 0.42 m 2 ; Pore Size = 0.1 µm; Temperature = 30.7º C)<br />
Flowrate<br />
Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
14 34 45 6<br />
32 76 88 12<br />
48 115 138 18<br />
57 135 160 21<br />
65 155 183 24<br />
Table D-2 Experimental Data for Determination <strong>of</strong> Initial Membrane Resistance <strong>of</strong> YMBR<br />
Membrane (A = 0.42 m 2 ; Pore Size = 0.1 µm; Temperature = 30.7º C)<br />
Flowrate<br />
Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
15 37 55 7<br />
22 52 70 9<br />
36 86 110 14<br />
49 117 153 20<br />
62 147 187 25<br />
156
Table D-3 Experimental Data for Determination <strong>of</strong> Initial Membrane Resistance in YMBR<br />
after Cleaning<br />
(a)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
2.29 5.4 8 1.1<br />
3.92 9.3 19 2.5<br />
8.05 19.2 32 4.2<br />
13.10 31.2 36 4.7<br />
(b)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
3.00 7.1 78 10.3<br />
3.03 7.2 80 10.5<br />
3.11 7.4 84 11.1<br />
3.36 8.0 88 11.6<br />
3.55 8.4 90 11.8<br />
(c)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
0.48 7.1 78 10.3<br />
0.72 7.2 80 10.5<br />
1.02 7.4 84 11.1<br />
1.50 8.0 88 11.6<br />
2.88 8.4 90 11.8<br />
157
Pressure (kPa)<br />
Pressure (kPa)<br />
Pressure (kPa)<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
0<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
Figure D-1 Graphs Showing Initial Membrane Resistance in YMBR after Cleaning<br />
158<br />
R 2 = 0.8687<br />
0 5 10 15 20 25 30 35<br />
Flux (L/m 2 .h)<br />
(a)<br />
y = 0.7997x - 1.1956<br />
R 2 = 0.9186<br />
10.0 10.5 11.0<br />
Flux (L/m<br />
11.5 12.0<br />
2 .h)<br />
(b)<br />
y = 0.2911x + 6.0323<br />
R 2 = 0.9239<br />
0 2 4 6 8<br />
Flux (L/m 2 .h)<br />
(c)
Table D-4 Experimental Data for Determination <strong>of</strong> Initial Membrane Resistance in BMBR<br />
after Cleaning<br />
(a)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
2.29 5.4 32 4.2<br />
3.92 9.3 40 5.3<br />
8.05 19.2 66 8.7<br />
13.10 31.2 80 10.5<br />
17.02 40.5 162 21.3<br />
(b)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
0.92 2.2 40 5.2<br />
5.72 13.6 53 7.0<br />
8.59 20.5 71 9.3<br />
10.88 25.9 77 10.1<br />
16.42 39.1 104 13.7<br />
19.56 46.6 122 16.1<br />
(c)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
0.6 2.0 76 10.0<br />
1.0 3.6 86 11.3<br />
4.5 16.3 106 13.9<br />
7.1 17.1 125 16.4<br />
11.4 41.2 160 21.1<br />
(d)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
6.00 14.3 64 8.4<br />
6.18 14.7 68 8.9<br />
6.48 15.4 70 9.2<br />
6.78 16.1 72 9.5<br />
6.90 16.4 76 10.0<br />
159
(e)<br />
Flowrate Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
1.56 3.7 78 10.4<br />
4.20 10.0 82 10.9<br />
8.28 19.7 95 12.7<br />
8.52 20.3 96 12.8<br />
11.22 26.7 108 14.4<br />
19.68 46.9 138 18.4<br />
Table D-5 Experimental Data for Determination <strong>of</strong> Initial Membrane Resistance <strong>of</strong> 2 nd<br />
Membrane in (a) BMBR and (b) YMBR<br />
(a)<br />
Flowrate<br />
Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
0.5 1.2 74 9.9<br />
1.2 2.9 78 10.4<br />
3.2 7.6 82 10.9<br />
5.2 12.4 84 11.2<br />
9.9 23.6 102 13.6<br />
(b)<br />
Flowrate<br />
Permeate Flux<br />
Trans-membrane Pressure<br />
(L/h)<br />
(L/m 2 .h) (mmHg) (kPa)<br />
0.5 1.2 65 8.7<br />
1.2 2.9 68 9.1<br />
2.0 4.8 72 9.6<br />
3.2 7.6 82 10.9<br />
5.2 12.4 84 11.2<br />
9.9 23.6 102 13.6<br />
160
Pressure (kPa)<br />
Pressure (kPa)<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
R 2 = 0.868<br />
0.0 10.0 20.0 30.0 40.0 50.0<br />
Flux (L/m 2 .h)<br />
(a)<br />
R2 25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
= 0.9514<br />
0.0 20.0 40.0 60.0<br />
Flux (L/m 2 .h)<br />
(c)<br />
Pressure (kPa)<br />
20<br />
15<br />
10<br />
5<br />
0<br />
Figure D-2 Graphs Showing Initial Membrane Resistance in BMBR after Cleaning<br />
161<br />
Pressure (kPa)<br />
Pressure (kPa)<br />
20<br />
15<br />
10<br />
5<br />
0<br />
11<br />
10<br />
10<br />
9<br />
9<br />
8<br />
R 2 = 0.9889<br />
0.0 10.0 20.0 30.0 40.0 50.0<br />
Flux (L/m 2 .h)<br />
(b)<br />
R 2 = 0.9291<br />
14.0 14.5 15.0 15.5 16.0 16.5 17.0<br />
R 2 = 0.9881<br />
0.0 10.0 20.0 30.0 40.0 50.0<br />
Flux (L/m 2 .h)<br />
(e)<br />
Flux (L/m 2 .h)<br />
(d)
Trans-membrane Pressure<br />
(kPa)<br />
Trans-membrane Pressure<br />
(kPa)<br />
15<br />
10<br />
15<br />
10<br />
5<br />
0<br />
5<br />
0<br />
Figure D-3 Graphs Showing Initial Membrane Resistance <strong>of</strong> 2 nd Membrane in (a) BMBR<br />
and (b) YMBR<br />
162<br />
y = 0.1568x + 9.7058<br />
R 2 = 0.9634<br />
0.0 5.0 10.0 15.0 20.0 25.0<br />
Permeate Flux (L/m 2 .h)<br />
(a)<br />
y = 0.2161x + 8.6241<br />
R 2 = 0.9671<br />
0.0 5.0 10.0 15.0 20.0 25.0<br />
Permeate Flux (L/m 2 .h)<br />
(b)
Appendix E<br />
MBR wi<strong>th</strong>out Ammonia Stripping<br />
163
Table E-1 Feed, Re<strong>ac</strong>tor and Effluent Char<strong>ac</strong>teristics in BMBR<br />
Day HRT<br />
(h) pH COD<br />
(mg/L)<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
NH3-N<br />
(mg/L)<br />
TKN<br />
(mg/L) pH<br />
164<br />
DO<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD<br />
Loading<br />
(kg/m 3 .d)<br />
F/M<br />
Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
1 24 7.2 7,384 7.4 5.3 12,800 7.38 0.58<br />
5 24 7.3 7,140 7.4 4.8 10,980 7.14 0.67 3,094 57<br />
8 24 7.7 7,736 7.2 5.6 7.74 2,618 66<br />
9 24 7.3 6,752 1,705 1,705 7.0 5.0 6.75 3,174 1,319 1,266 53 26<br />
16 24 7.3 7,981 1,843 1,852 7.0 6.1 10,950 7.98 0.73 2,777 1,356 65 26<br />
22 24 7.5 8,331 1,618 1,619 7.0 2.8 11,450 8.33 0.73 3,253 1,230 61 24<br />
26 20 7.4 6,336 7.0 2.6 7.60 2,611 59<br />
28 20 7.3 9,216 1,704 1,967 6.9 3.5 11.06 4,562 1,336 1,285 50 35<br />
35 20 7.0 9,094 1,459 1,653 6.8 2.6 14,167 10.91 0.77 3,375 1,173 1,110 63 24<br />
43 20 7.4 7,938 1,278 1,376 7.0 4.2 9.53 1,883 1,031 955 76 13<br />
48 20 7.6 9,281 1,260 1,764 7.2 3.1 11.14 0.60 2,936 1,482 1,233 68 16<br />
54 20 7.6 9,281 6.9 4.0 12,600 11.14 0.66 2,618 72<br />
61 16 7.4 7,442 1,536 1,796 6.9 3.8 11.16 0.68 2,764 1,279 1,221 58 29<br />
66 16 7.0 9,322 1,511 1,960 7.1 4.5 11,900 13.98 1.36 2,618 1,384 1,233 72 29<br />
68 16 7.5 9,322 6.9 3.1 12,733 13.98 1.10 3,134 66<br />
72 16 7.3 7,282 1,217 1,698 6.8 3.5 12,000 10.92 1.06 1,764 1,324 1,196 76 22<br />
78 16 7.8 6,358 1,735 1,837 6.9 3.6 9.54 3,077 1,246 1,194 52 25<br />
83 16 7.5 7,415 7.0 4.2 13,000 11.12 0.99 2,576 65<br />
89 16 7.9 8,529 1,735 1,837 7.0 3.6 12.79 1.66 3,282 1,378 1,221 61 25<br />
90 16 8.2 8,529 1,232 1,560 6.9 3.3 10,067 12.79 1.47 3,332 1,237 1,176 61 15<br />
94 16 8.1 7,759 7.0 3.0 14,400 11.64 0.94 3,248 58<br />
97 16 8.5 8,735 1,764 7.0 3.2 9,667 13.10 1.57 3,282 1,482 1,233 62 16<br />
104 16 8.7 8,662 7.0 4.6 13,700 12.99 1.10 3,320 62<br />
107 16 8.7 8,662 1,796 6.8 4.1 12.99 1.00 3,077 1,384 1,185 64 23
Day HRT<br />
(h) pH COD<br />
(mg/L)<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
NH3-N<br />
(mg/L)<br />
TKN<br />
(mg/L) pH<br />
165<br />
DO<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD<br />
Loading<br />
(kg/m 3 .d)<br />
F/M<br />
Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
117 16 8.2 9,600 7.2 3.1 12,333 14.40 1.86 3,282 66<br />
119 16 8.4 6,957 2,045 2,253 7.1 4.2 14,067 10.43 0.86 3,140 1,515 1,460 55 35<br />
124 16 8.2 8,735 1,691 2,145 7.3 2.2 13.10 1.32 4,182 1,389 1,322 67 27<br />
130 16 7.4 7,938 1,778 2,156 7.2 2.6 11,600 11.91 1.31 3,653 1,497 1,439 58 31<br />
136 16 7.4 7,938 1,106 1,613 7.0 3.2 11,567 11.91 1.40 3,282 1,258 1,176 59 22<br />
141 16 8.2 7,759 8.4 2.3 10,900 11.64 1.07 3,320 57<br />
145 16 7.9 7,646 1,837 2,093 8.3 7.6 13,533 11.47 1.39 3,077 1,581 1,361 60 24<br />
150 12 8.2 8,938 2,066 8.3 0.6 10,900 17.88 2.41 3,896 56<br />
157 12 8.5 8,000 1,831 2,013 8.8 6.6 12,333 16.00 1.98 4,308 1,753 1,574 46 13<br />
164 12 8.1 7,344 1,540 1,837 7.1 1.8 11,567 14.69 1.79 3,830 1,504 1,358 48 18<br />
169 12 8.0 7,077 1,590 1,876 7.1 3.8 11,000 14.15 1.56 3,538 1,649 1,355 50 12<br />
173 12 8.1 7,076 1,562 1,848 7.0 5.7 10,233 14.15 1.62 3,231 1,658 1,364 54 10<br />
176 12 8.1 7,050 1,604 1,893 7.1 4.5 13,533 14.10 1.52 3,450 1,672 1,403 51 12<br />
179 12 8.1 7,077 1,649 1,960 7.1 2.8 11,567 14.15 1.90 3,538 1,593 1,324 50 19<br />
181 12 8.2 6,962 1,607 1,893 7.1 3.6 11,000 13.92 1.91 3,073 1,688 1,464 56 11
Table E-2 Feed, Re<strong>ac</strong>tor and Effluent Char<strong>ac</strong>teristics in YMBR<br />
Day HRT<br />
(h) pH COD<br />
(mg/L)<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
NH3-N<br />
(mg/L)<br />
TKN<br />
(mg/L) pH<br />
166<br />
DO<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD<br />
Loading<br />
(kg/m 3 .d)<br />
F/M<br />
Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
1 24 7.2 7,384 3.6 5.0 8,940 7.38 0.83<br />
5 24 7.3 7,140 3.6 4.0 11,650 7.14 0.61 3,015 58<br />
8 24 7.7 7,736 3.6 7.9 7.74 2,380 69<br />
9 24 7.3 6,752 1,705 1,705 3.6 7.3 6.75 2,460 1,221 1,221 64 28<br />
16 24 7.3 7,987 3.6 7.9 7.99 3,015 62<br />
17 24 7.5 7,981 1,843 1,852 3.6 7.9 10,820 7.98 0.74 3,094 1,336 1,285 61 28<br />
22 24 7.5 8,331 1,618 1,619 3.6 8.0 8.33 3,332 60<br />
24 24 7.4 8,504 3.6 8.0 8.50 3,099 64<br />
26 20 7.3 6,336 3.6 7.6 7.60 3,456<br />
28 20 7.0 9,216 1,704 1,967 3.6 3.9 11.06 3,295 1,611 1,515 64 18<br />
35 20 7.4 9,094 1,459 1,653 3.6 4.0 12,180 10.91 1.04 3,563 1,322 1,252 61 20<br />
40 20 7.6 9,744 3.6 4.2 9,720 11.69 1.40 2,959 70<br />
43 20 7.6 7,938 1,278 1,376 3.6 4.8 9.53 3,286 59<br />
48 20 7.0 9,281 1,260 1,764 3.6 4.2 11.14 0.78 3,563 1,159 1,036 62 34<br />
54 20 6.7 9,281 1,449 3.6 4.9 11,867 11.14 0.87 1,002 918 31<br />
57 20 7.4 8,372 3.6 4.6 10,567 7.64 0.95 2,489 61<br />
61 16 7.0 7,442 1,536 1,796 3.6 4.0 11.16 0.62 2,800 1,226 823 62 32<br />
66 16 7.5 9,322 3.6 3.4 13.98 1.02 2,698 71<br />
68 16 7.5 9,322 1,511 1,960 3.6 3.4 13,033 13.98 1.24 2,579 1,567 1,484 72 20<br />
72 16 7.3 7,282 1,217 1,698 3.6 3.5 11,700 10.92 1.08 1,862 1,378 1,221 74 19<br />
78 16 7.8 6,358 1,837 3.6 3.6 12,433 9.54 0.89 1,345 1,284 27<br />
84 16 7.5 7,415 1,735 1,837 3.6 4.6 11,600 11.12 1.11 2,831 1,194 1,194 62 35<br />
88 16 7.9 7,415 1,232 1,560 3.6 3.5 11,933 11.12 1.08 2,576 1,322 1,106 65 15<br />
90 16 8.2 8,529 1,232 1,560 3.6 2.0 10,367 12.79 1.43 2,142 75<br />
94 16 8.1 7,759 3.6 2.0 13,067 11.64 1.03 3,104 60
Day HRT<br />
(h) pH COD<br />
(mg/L)<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
NH3-N<br />
(mg/L)<br />
TKN<br />
(mg/L) pH<br />
167<br />
DO<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD<br />
Loading<br />
(kg/m 3 .d)<br />
F/M<br />
Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
104 16 8.5 8,662 3.6 3.3 10,000 12.99 1.51 3,176 63<br />
107 16 8.7 8,662 1,796 3.6 4.6 12,600 12.99 1.20 3,409 1,279 1,176 61 29<br />
117 16 8.7 9,600 3.6 4.9 11,367 14.40 1.47 3,757 61<br />
119 16 8.2 6,957 2,045 2,253 3.6 3.7 12,333 10.43 0.98 2,769 1,440 818 60 36<br />
124 16 8.4 8,735 1,691 2,145 3.6 4.7 9,533 13.10 1.59 2,470 1,389 1,221 72 35<br />
130 16 8.2 7,938 1,778 2,156 3.6 3.5 12,700 11.91 1.09 1,985 1,482 1,110 75 31<br />
136 16 7.4 7,938 1,106 1,613 3.6 4.8 11,367 11.91 1.22 2,483 69<br />
141 16 7.4 7,759 1,613 3.6 3.2 12,700 11.64 1.06 3,070 1,313 60 19<br />
148 16 8.2 7,646 1,854 3.6 5.2 10,233 15.29 1.49 2,146 72<br />
150 12 7.9 8,938 2,066 3.6 3.5 10,900 17.88 1.64 3,320 1,581 1,358 63 23<br />
157 12 8.2 8,000 1,831 2,013 3.6 0.4 11,867 16.00 1.35 3,231 60<br />
160 12 8.5 8,566 2,093 3.6 6.9 10,833 17.13 1.58 4,273 1,798 1,610 50 11<br />
164 12 8.1 7,344 1,540 1,837 3.6 2.5 11,567 14.69 1.27 3,515 1,456 1,331 52 15<br />
169 12 8.0 7,077 1,590 1,876 3.6 6.1 11,867 14.15 1.19 3,385 1,504 1,352 52 20<br />
173 12 8.1 7,076 1,562 1,848 3.6 2.6 11,900 14.15 1.19 3,038 1,512 1,361 57 18<br />
176 12 8.1 7,050 1,604 1,893 3.6 3.2 13,533 14.10 1.04 3,300 1,599 1,375 53 16<br />
179 12 8.1 7,077 1,649 1,960 3.6 6.7 10,600 10.62 1.16 2,769 1,576 1,369 61 20<br />
181 12 8.2 6,962 1,607 1,893 3.6 3.9 11,867 10.44 1.02 3,231 54
TKN (mg/L)<br />
TKN (mg/L)<br />
TKN (mg/L)<br />
2500<br />
2000<br />
1500<br />
1000<br />
500<br />
2500<br />
2000<br />
1500<br />
1000<br />
500<br />
0<br />
0<br />
2500<br />
2000<br />
1500<br />
1000<br />
500<br />
1 17 35 57 78 104 130 157 176<br />
Time (days)<br />
0<br />
(a)<br />
0 16 32 48 64 80 96 112 128 144 160 176<br />
Time (days)<br />
Influent TK N Effluent TK N HRT<br />
Figure E-1 Influent and Effluent TKN Concentration in (a) YMBR and (b) BMBR<br />
168<br />
24<br />
22<br />
20<br />
18<br />
16<br />
14<br />
12<br />
10<br />
0 16 32 48 64 80 96 112 128 144 160 176<br />
Time (days)<br />
24<br />
22<br />
20<br />
18<br />
16<br />
14<br />
12<br />
10<br />
24<br />
22<br />
20<br />
18<br />
16<br />
14<br />
12<br />
10<br />
Influent TKN Effluent TKN HRT<br />
(b)<br />
HRT (h)<br />
HRT (h)<br />
HRT (h)
Table E-3 Variation in TMP wi<strong>th</strong> Time in BMBR<br />
Day HRT (h) TMP (kPa) Day HRT (h) TMP (kPa)<br />
1 24 7.37 120 16 16.84<br />
5 24 9.21 122 16 17.11<br />
10 24 7.89 123 16 31.58<br />
15 24 6.84 124 16 56.58<br />
20 24 6.32 125 16 65.79<br />
25 24 6.84 129 16 11.84<br />
30 20 9.47 132 16 12.37<br />
35 20 8.16 135 16 15.79<br />
40 20 8.42 136 16 19.21<br />
45 20 9.21 137 16 36.84<br />
50 20 10.00 138 16 44.47<br />
55 20 11.32 141 16 56.32<br />
57 20 11.05 142 16 65.79<br />
58 20 14.47 143 16 8.95<br />
60 20 13.42 149 16 15.46<br />
61 16 17.89 150 12 18.93<br />
62 16 18.68 151 12 24.53<br />
65 16 7.63 152 12 26.66<br />
69 16 7.89 153 12 29.86<br />
72 16 11.84 158 12 33.59<br />
77 16 12.11 159 12 38.39<br />
81 16 13.68 160 12 35.19<br />
82 16 17.11 161 12 34.12<br />
85 16 22.11 162 12 34.12<br />
89 16 7.89 163 12 36.25<br />
90 16 10.53 164 12 38.12<br />
91 16 10.92 165 12 37.85<br />
96 16 11.45 166 12 43.19<br />
100 16 11.84 169 12 12.00<br />
103 16 13.16 173 12 13.06<br />
104 16 15.79 177 12 13.06<br />
114 16 15.79 181 12 15.20<br />
169
Table E-4 Variation in TMP wi<strong>th</strong> Time in YMBR<br />
Day HRT (h) TMP (kPa) Day HRT (h) TMP (kPa)<br />
1 24 9.3 91 16 6.91<br />
5 24 9.3 96 16 6.91<br />
10 24 7.4 100 16 7.58<br />
15 24 9.0 103 16 8.24<br />
21 24 8.0 104 16 8.24<br />
25 24 8.2 107 16 10.63<br />
30 20 8.0 108 16 13.29<br />
35 20 7.4 109 16 18.61<br />
45 20 6.9 110 16 20.20<br />
50 20 7.2 114 16 6.64<br />
55 20 7.7 122 16 5.32<br />
57 20 9.0 129 16 5.32<br />
58 20 8.4 132 16 8.77<br />
60 20 8.8 137 16 9.57<br />
61 16 8.8 143 16 10.90<br />
62 16 8.4 153 12 13.02<br />
69 16 7.0 159 12 17.54<br />
72 16 8.2 160 12 25.25<br />
77 16 6.6 161 12 27.91<br />
81 16 8.0 162 12 28.17<br />
82 16 8.0 163 12 28.57<br />
85 16 8.0 166 12 7.18<br />
88 16 14.6 173 12 10.90<br />
89 16 18.6 178 12 11.43<br />
90 16 20.2 181 12 10.37<br />
170
Appendix F<br />
Ammonia Stripping Studies<br />
171
Table F-1 Ammonia Removal Efficiency in Le<strong>ac</strong>hate wi<strong>th</strong> Varying pH<br />
Initial Concentration<br />
Ammonia Stripping (%)<br />
(mg/L)<br />
pH 9 pH 10 pH 11 pH 12<br />
1,106 16 24 38 43<br />
1,366 23 32 45 50<br />
1,380 25 30 42 47<br />
Table F-2 Experimental Data <strong>of</strong> Ammonia Concentration at a pH from 11 to 12 <strong>of</strong><br />
Le<strong>ac</strong>hate as Functions <strong>of</strong> Cont<strong>ac</strong>t Time and Velocity Gradient (Run I: 1,106 mg/L)<br />
Velocity<br />
Gradient<br />
(s<br />
2 h<br />
Cont<strong>ac</strong>t Time<br />
4 h 6 h<br />
-1 )<br />
NH3 Removal<br />
(mg/L) (%)<br />
NH3 Removal<br />
(mg/L) (%)<br />
NH3 Removal<br />
(mg/L) (%)<br />
0 767 30 602 45 543 51<br />
1,530 378 66 174 84 73 93<br />
2,850 298 73 60 95 25 98<br />
4,330 269 76 56 95 20 98<br />
Table F-3 Experimental Data <strong>of</strong> Ammonia Concentration at a pH from 11 to 12 <strong>of</strong><br />
Le<strong>ac</strong>hate as Functions <strong>of</strong> Cont<strong>ac</strong>t Time and Velocity Gradient (Run II: 1,366 mg/L)<br />
Velocity<br />
Gradient<br />
(s<br />
2 h<br />
Cont<strong>ac</strong>t Time<br />
4 h 6 h<br />
-1 )<br />
NH3 Removal<br />
(mg/L) (%)<br />
NH3 Removal<br />
(mg/L) (%)<br />
NH3 Removal<br />
(mg/L) (%)<br />
0 986 28 829 39 689 50<br />
1,530 459 66 190 86 106 92<br />
2,850 353 74 98 93 34 98<br />
4,330 325 76 78 94 28 98<br />
Table F-4 Experimental Data <strong>of</strong> Ammonia Concentration at a pH from 11 to 12 <strong>of</strong><br />
Le<strong>ac</strong>hate as Functions <strong>of</strong> Cont<strong>ac</strong>t Time and Velocity Gradient (Run III: 1,380 mg/L)<br />
Velocity<br />
Gradient<br />
(s<br />
2 h<br />
Cont<strong>ac</strong>t Time<br />
4 h 6 h<br />
-1 )<br />
NH3 Removal<br />
(mg/L) (%)<br />
NH3 Removal<br />
(mg/L) (%)<br />
NH3 Removal<br />
(mg/L) (%)<br />
0 994 28 876 37 736 47<br />
1,530 540 61 216 84 160 88<br />
2,850 434 69 165 88 59 96<br />
4,330 406 71 148 89 53 96<br />
172
Table F-5 Pilot Scale Study on Ammonia Stripping wi<strong>th</strong> Varying Cont<strong>ac</strong>t Time (Re<strong>ac</strong>tor<br />
Volume 40 L, pH 11-12, Velocity Gradient 2,850 s -1 )<br />
Initial<br />
Cont<strong>ac</strong>t Time<br />
Concentration 1 h 2 h 3 h 4 h 5 h<br />
(mg/L) NH3 R NH3 R NH3 R NH3 R NH3 R<br />
(mg/L) (%) (mg/L) (%) (mg/L) (%) (mg/L) (%) (mg/L) (%)<br />
1,160 722 38 487 58 235 80 202 83 104 91<br />
1,473 902 22 675 42 375 68 266 77 140 88<br />
* R – Ammonia Removal Efficiency<br />
Table F-6 Verification <strong>of</strong> <strong>th</strong>e Optimum Parameters for <strong>th</strong>e Ammonia Stripping Studies<br />
wi<strong>th</strong> Varying Ammonia Concentration in <strong>th</strong>e Le<strong>ac</strong>hate (Velocity Gradient: 2,850 s -1 , pH:<br />
11-12, Cont<strong>ac</strong>t Time: 5 h)<br />
Sample No.<br />
Ammonia Concentration (mg/L)<br />
Initial Final<br />
Removal Efficiency (%)<br />
1 1,473 140 90<br />
2 1,546 148 91<br />
3 1,310 151 88<br />
4 1,753 218 88<br />
5 1,546 241 84<br />
6 1,414 227 84<br />
7 1,358 202 85<br />
8 1,277 210 84<br />
9 1,369 218 84<br />
10 1,442 238 83<br />
11 1,389 179 87<br />
12 1,490 162 89<br />
13 1,532 218 86<br />
14 1,473 140 90<br />
15 1,546 148 91<br />
Average 1,455 196 86<br />
173
Appendix G<br />
MBR wi<strong>th</strong> Ammonia Stripping<br />
174
Table G-1 Feed, Re<strong>ac</strong>tor and Effluent Char<strong>ac</strong>teristics in BMBR at 16 h HRT<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
Day COD<br />
(mg/L)<br />
TKNRaw<br />
(mg/L)<br />
TKNStripp<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD Loading<br />
(kg/m 3 .d)<br />
F/M Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
1 7,538 1,686 11,567 11.31 1.09 2,769<br />
7 6,987 1,473 11,567 10.48 1.08 2,430 403 252 65 73<br />
14 8,467 1,739 11,000 12.70 1.52 2,780 454 367 67 74<br />
16 8,930 1,957 11,567 13.40 1.21 2,791 456 342 69 77<br />
19 8,964 1,828 11,000 13.45 1.21 2,747 462 347 69 75<br />
23 7,459 1,764 445 11,000 11.19 1.02 2,634 473 347 65 73<br />
27 7,167 1,614 445 12,667 10.75 0.85 1,933 353 227 73 78<br />
33 7,459 1,764 451 10,750 11.19 1.04 2,270 347 227 70 80<br />
39 7,277 1,557 213 10,500 10.92 1.04 2,143 71<br />
48 8,269 1,473 157 11,100 12.40 1.12 2,742 67<br />
57 8,195 1,414 204 11,850 12.29 0.82 2,500 255 168 69 82<br />
62 7,277 1,322 179 11,700 10.92 0.93 1,677 241 210 77 82<br />
67 6,857 12,450 10.29 0.62 1,739 75<br />
69 9,231 1,982 344 12,050 13.85 1.15 2,571 322 210 72 84<br />
71 9,231 11,850 13.85 1.17 2,031 78<br />
77 8,432 1,834 350 11,100 12.65 1.14 1,500 188 140 82 90<br />
84 7,000 1,912 395 10,450 10.50 1.00 1,667 272 210 76 86<br />
92 7,000 1,789 372 11,600 10.50 0.91 2,000 238 168 71 87<br />
99 6,733 1,582 333 12,050 10.10 0.50 1,833 224 140 73 86<br />
108 7,167 1,646 358 10,300 10.75 0.51 1,933 232 168 73 86<br />
114 7,784 1,593 330 11,700 11.68 1.19 2,060 280 210 74 82<br />
120 7,162 1,764 325 10,550 10.74 1.09 1,709 168 137 76 90<br />
126 7,084 11,700 10.63 1.12 2,234 68<br />
133 7,167 11,750 10.75 0.90 1,870 74<br />
140 6,857 1,795 288 11,750 10.29 0.70 2,026 244 157 70 86<br />
147 7,040 1,879 249 10,600 10.56 0.79 2,080 216 151 70 89<br />
153 7,610 10,750 11.42 0.84 1,538 80<br />
159 7,667 1,876 311 11,800 11.50 0.77 2,026 187 145 74 90<br />
170 7,720 10,750 11.58 0.64 1,538 80<br />
175
Table G-2 Feed, Re<strong>ac</strong>tor and Effluent Char<strong>ac</strong>teristics in BMBR at 24 h HRT<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
Day COD<br />
(mg/L)<br />
TKNRaw<br />
(mg/L)<br />
TKNStripp<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD Loading<br />
(kg/m 3 .d)<br />
F/M<br />
Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
1 7,655 1,646 358 11,300 7.66 0.68 1,862 232 168 76 86<br />
5 7,500 12,550 7.50 0.60<br />
13 8,262 1,574 342 12,050 8.26 0.69 1,655 151 126 80 90<br />
14 7,655 10,133 7.66 0.76 1,742 77<br />
17 8,129 1,582 333 11,850 8.13 0.69 2,032 224 140 75 86<br />
24 8,262 12,750 8.26 0.65<br />
30 7,655 2,041 361 11,600 7.66 0.66 162 109 92<br />
35 8,129 13,467 8.13 0.60<br />
42 9,322 1,876 311 12,750 9.32 0.73 2,531 216 157 73 88<br />
46 7,500 12,033 7.50 0.62<br />
49 9,223 11,300 9.22 0.82 2,344 75<br />
52 9,223 11,233 9.22 0.82 2,430 74<br />
58 8,852 13,467 8.85 0.66 2,164 76<br />
176
Table G-3 Feed, Re<strong>ac</strong>tor and Effluent Char<strong>ac</strong>teristics in YMBR at 16 h HRT<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
Day COD<br />
(mg/L)<br />
TKNRaw<br />
(mg/L)<br />
TKNStripp<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD Loading<br />
(kg/m 3 .d)<br />
F/M Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
1 7,538 1,686 10,833 11.31 2.08 2,769<br />
7 6,987 1,473 10,933 10.48 2.01 2,127 70<br />
14 1,739 12,567 14.05 0.93 2,780 521 395 70 70<br />
16 8,930 1,957 10,933 13.40 1.05 2,791 448 316 69 77<br />
19 8,964 1,828 11,250 13.45 1.19 2,747 459 333 69 75<br />
23 7,459 1,764 445 12,267 11.19 1.06 2,195 353 238 71 80<br />
27 7,167 1,614 445 10,850 10.75 0.96 1,864 322 210 74 80<br />
33 7,459 1,764 451 11,600 11.19 0.96 2,571 339 221 66 81<br />
39 7,459 1,557 213 10,750 11.19 1.24 2,261 70<br />
48 8,269 1,473 157 12,100 12.40 1.02 2,714 126 115 67 91<br />
57 8,195 1,414 204 12,400 12.29 0.66 2,667 233 199 67 84<br />
62 7,277 1,322 179 10,900 10.92 1.06 1,223 193 185 83 85<br />
67 6,514 11,250 9.77 0.92 1,739 73<br />
69 9,231 1,982 344 11,700 13.85 1.25 2,571 274 184 72 86<br />
71 9,231 12,100 13.85 1.10 1,846 80<br />
77 8,432 1,834 350 10,900 12.65 1.27 2,250 241 146 73 87<br />
84 7,000 1,912 395 11,050 10.50 0.91 1,743 224 185 75 88<br />
92 7,000 1,789 372 11,750 10.50 0.95 2,167 216 199 69 88<br />
99 6,733 1,582 333 11,600 10.10 0.75 2,000 277 146 70 82<br />
108 7,167 1,646 358 12,200 10.75 0.99 2,100 210 199 71 87<br />
114 7,784 1,593 330 11,950 11.68 1.23 2,166 232 185 72 85<br />
120 7,162 1,764 325 11,400 10.74 1.09 1,565 221 143 78 87<br />
126 7,084 11,750 10.63 0.69 1,940 73<br />
133 7,167 11,950 10.75 0.90 1,558 78<br />
140 6,857 1,795 288 11,950 10.29 0.63 2,026 252 162 70 86<br />
147 7,040 1,879 249 11,550 10.56 0.73 1,920 232 148 73 88<br />
153 7,610 11,600 11.42 0.98 1,846 76<br />
159 7,667 1,876 311 11,750 11.50 1.04 2,054 220 150 73 88<br />
170 7,720 11,600 11.58 0.66 1,846 76<br />
177
Table G-4 Feed, Re<strong>ac</strong>tor and Effluent Char<strong>ac</strong>teristics in YMBR at 24 h HRT<br />
Feed Re<strong>ac</strong>tor Effluent Removal (%)<br />
Day COD<br />
(mg/L)<br />
TKNRaw<br />
(mg/L)<br />
TKNStripp<br />
(mg/L)<br />
MLSS<br />
(mg/L)<br />
COD Loading<br />
(kg/m 3 .d)<br />
F/M<br />
Ratio<br />
COD<br />
(mg/L)<br />
TKN<br />
(mg/L)<br />
NH3-N<br />
(mg/L)<br />
COD TKN<br />
1 7,655 1,646 358 11,550 7.66 0.66 1,742 232 148 77 86<br />
5 7,500 11,400 7.50 0.66<br />
13 8,262 1,574 342 12,200 8.26 0.68 1,655 137 109 80 91<br />
14 7,655 12,933 7.66 0.59 1,655 78<br />
17 8,129 1,582 333 11,750 8.13 0.69 1,935 216 146 76 86<br />
24 7,655 12,650 7.66 0.61<br />
30 7,655 2,041 361 11,550 7.66 0.66 157 115 92<br />
35 8,129 12,200 8.13 0.67<br />
42 9,322 1,876 311 12,333 9.32 0.76 2,719 221 143 71 88<br />
46 7,500 11,133 7.50 0.67 2,164 71<br />
49 9,223 11,550 9.22 0.80<br />
52 9,223 12,333 9.22 0.75 2,430 74<br />
58 8,852 12,200 8.85 0.73 2,066 77<br />
178
Appendix H<br />
O<strong>th</strong>er Studies<br />
179
Table H-1 20 Days BOD <strong>of</strong> Raw Le<strong>ac</strong>hate, Stripped Le<strong>ac</strong>hate, B<strong>ac</strong>terial and Yeast<br />
Effluents<br />
Day<br />
Raw<br />
Le<strong>ac</strong>hate<br />
BOD (mg/L)<br />
Stripped Le<strong>ac</strong>hate<br />
YMBR<br />
Effluent<br />
BMBR<br />
Effluent<br />
1 2,080 240 10 5<br />
2 2,640 440 15 10<br />
3 3,040 640 15 10<br />
4 3,280 1,000 20 15<br />
5 3,520 1,120 20 15<br />
6 3,760 1,200 20 20<br />
7 4,080 1,280 25 20<br />
8 4,240 1,480 30 25<br />
9 4,480 1,920 35 25<br />
10 4,560 2,040 35 25<br />
11 4,720 2,200 40 25<br />
12 4,800 2,280 45 25<br />
13 4,800 2,400 50 25<br />
14 4,960 2,440 60 30<br />
15 4,960 2,400 65 30<br />
16 5,040 2,400 70 35<br />
17 5,120 2,400 75 35<br />
18 5,120 2,400 75 35<br />
19 5,200 2,400 80 35<br />
20 5,280 2,400 80 40<br />
COD (mg/L) 7,742 6,581 1,839 1,742<br />
BOD5 (mg/L) 3,520 1,120 20 15<br />
BOD5/COD 0.45 0.17 0.01 0.01<br />
BOD10/COD 0.59 0.31 0.02 0.01<br />
BOD15/COD 0.64 0.36 0.04 0.02<br />
BOD20/COD 0.68 0.36 0.04 0.02<br />
180
Table H-2 Membrane Resistance <strong>of</strong> <strong>th</strong>e Membrane Used for MWCO Studies<br />
Pressure<br />
(kPa)<br />
Flowrate<br />
(L/h)<br />
MW 50k MW 10k MW 5k<br />
Permeate<br />
Flux<br />
(L/m 2 .h)<br />
Flowrate<br />
(L/h)<br />
181<br />
Permeate<br />
Flux<br />
(L/m 2 .h)<br />
Flowrate<br />
(L/h)<br />
Permeate<br />
Flux<br />
(L/m 2 .h)<br />
101 0.53 117.78 0.31 68.02 - -<br />
202 0.79 174.68 0.65 143.18 0.18 40.76<br />
303 1.13 249.78 0.99 217.29 0.26 57.70<br />
404 1.32 290.47 1.31 288.22 0.36 79.93<br />
505 1.52 335.47 1.42 313.90 0.45 99.25<br />
Membrane<br />
Resistance<br />
Pressure (kPa)<br />
600<br />
500<br />
400<br />
300<br />
200<br />
100<br />
0<br />
8.16 x 10 12 m -1 6.99 x 10 12 m -1 1.86 x 10 13 m -1<br />
Pressure (kPa)<br />
600<br />
400<br />
200<br />
0<br />
MW 5k<br />
0 50 100 150<br />
Permeate Flux (L/m 2 .h)<br />
Figure H-1 Determination <strong>of</strong> Initial Membrane Resistance <strong>of</strong> Flat Sheet Membrane<br />
(A = 45.34 cm 2 )<br />
Pressure (kPa)<br />
600<br />
400<br />
200<br />
0 100 200 300 400<br />
Permeate Flux (L/m 2 .h)<br />
0<br />
MW 50k<br />
MW 10k<br />
0 200 400<br />
Permeate Flux (L/m 2 .h)
Table H-3 COD Fr<strong>ac</strong>tion <strong>of</strong> Raw Le<strong>ac</strong>hate, Stripped Le<strong>ac</strong>hate and Yeast and B<strong>ac</strong>terial<br />
Membrane Biore<strong>ac</strong>tor Effluents at Different Molecular Weight<br />
Molecular<br />
Weight<br />
Raw Le<strong>ac</strong>hate<br />
COD COD<br />
Stripped Le<strong>ac</strong>hate<br />
COD COD<br />
Yeast Effluent<br />
COD COD<br />
B<strong>ac</strong>terial<br />
Effluent<br />
COD COD<br />
(mg/L) (%) (mg/L) (%) (mg/L) (%) (mg/L) (%)<br />
MW>50k 6,445 87 3,643 65 54 3 127 7<br />
MW 10k-50k 401 5 359 6 286 14 230 12<br />
MW 5k-10k 590 8 606 11 529 26 588 31<br />
MW50k 6,916 91 4,732 72 123 7 48 3<br />
MW 10k-50k 215 3 178 3 175 9 178 9<br />
MW 5k-10k 492 6 456 7 353 19 355 19<br />
MW50k 3,032 88 1,149 72 12 10 6 4<br />
MW 10k-50k 91 3 57 4 6 6 38 23<br />
MW 5k-10k 328 10 115 7 11 10 13 8<br />
MW
Table H-6 Chemical Cost for <strong>th</strong>e Yeast and B<strong>ac</strong>terial Membrane Biore<strong>ac</strong>tor wi<strong>th</strong> Ammonia<br />
Stripping<br />
Sample<br />
pH<br />
NaOH<br />
(kg/m 3 )<br />
183<br />
H2SO4<br />
(L/m 3 )<br />
NaOH*<br />
(kg/m 3 )<br />
Chemical<br />
Cost<br />
(Baht/m 3 )<br />
Raw Le<strong>ac</strong>hate 7.8 - - - -<br />
Stripped Le<strong>ac</strong>hate 11.5 15.25 (pH 11.5) - - 458<br />
YMBR Effluent 3.6 - 13.5 (pH 3.6) 0.5 (pH 7.0) 204<br />
BMBR Effluent 7.5 - 7.7 (pH 7.5) - 107<br />
Note * Increase in pH <strong>of</strong> YMBR effluent