Thesis - faculty.ait.ac.th - Asian Institute of Technology

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Table 2.14 Typical Reverse Osmosis Plant Performance for Leachate Purification, Germany (Peters, 1997). Parameter Unit Leachate RO Permeate I RO Permeate II Rejection (%) pH - 7.7 6.8 6.6 Electrical Conductivity µS/cm 17,250 382 20 99.9 COD mg O2/L 1,797 < 15 < 15 > 99.2 Ammonium mg/L 366 9.8 0.66 99.9 Chloride mg/L 2,830 48.4 1.9 99.9 Sodium mg/L 4,180 55.9 2.5 99.9 Heavy Metals mg/L 0.25 < 0.005 < 0.005 > 98 Evaporation As cited by Ehrig (1998), through evaporation, leachate can be separated into a clear liquid and a solid phase bearing the pollutants. Practically, this is difficult as the solid phase or the condensate laden with volatile or chlorinated organic compounds and ammonia requires further treatment. Concentration and nitrogen recovery with the evaporation technology is possible with evaporation technology. Physicalchemical leachate treatment plants consist of many technical points and equipments which have to be taken into account in the maintenance of the plant. Evaporation is a simpler technology with easy application and less complicated technical difficulties. Evaporation is also a cost-effective option. But, the problems concerned with evaporation of raw leachate as cited by Cossu, et al. (1992) are: 1. Formation of foam due to high organic content 2. Encrustation and corrosion, causing equipment damage 3. Fouling on the heat-transfer surface 4. Need for post-treatment for removal of ammonium and halogenated organic material 5. High energy costs. 2.8.3 Chemical Treatment A wide scope of chemical treatment is available for leachate treatment. The advantages of chemical treatment methods in general include immediate start-up, easy automation, insensitivity to temperature changes and simplicity of plant and material requirements. However, the advantages are outweighed by the disadvantages of large quantities of sludge generated due to the addition of flocculants and chemicals with high running costs. Thus, chemical and physical treatment is merely used as pre or posttreatment of leachate to complement biological processes. The various chemical treatment processes used in leachate treatment are coagulation, precipitation, oxidation, stripping, etc. Coagulation and Precipitation Coagulation/precipitation involves the addition of chemicals to alter the physical state of dissolved and suspended solids and facilitate removal by sedimentation. This treatment is effective on leachate with high molecular weight organic material such as fulvic and humic acid. Since these components are generally difficult to degrade 30
iologically, physical-chemical processes prove beneficial with approximately 60 % reduction in COD for methanogenic leachate. Lime as a precipitating agent can reduce colour upto 85% and remove metals through precipitation. Chian and DeWalle (1977) and Ho, et al. (1974) reported that precipitation using lime could remove organic matter with molecular weight greater than 50,000 Da. This particular fraction is present in a low concentration in young landfills and absent in older landfills. Therefore, lime treatment is most effective in medium-age landfills. Whilst easily biodegradable fatty acids are however impervious to coagulation/precipitation and hence should be treated biologically. The concurrent COD and phosphorus removal via lime precipitation is independent of air flow rate. The change in colour of the raw leachate from dark brown to pale yellow after precipitation indicated the removal of the organic fractions that contributed to the colour (humic substances). Chian and DeWalle (1976) mentioned that the minimal reduction in COD (20 %) could be attributed to lime precipitation, as the molecular weight greater than 50,000 Da contributing to some amount of COD fraction was removed. However, an increase in lime dosage did not prompt a concomitant increase in COD precipitation. Phosphorus was removed by calcium hydroxide precipitation. Chemical Oxidation Chemical oxidation technologies are useful in the oxidative degradation or transformation of a wide range of pollutants present in drinking water, groundwater and wastewater treatment (Venkatadri and Peters, 1993). Generally, chemical oxidation processes are incorporated into treatment sequences to treat constituents of wastewaters that are resistant to biodegradation or create toxicity in biological reactors. Chemical oxidation process is widely used in leachate treatment. A variety of chemical oxidants are used for leachate treatment. The various oxidants used for leachate treatment are hydrogen peroxide, ozone, chlorine, chlorine dioxide, hypochlorite, UV-radiation and wet oxidation. Based on the oxidative potentials, hydroxyl radicals exhibit a stronger oxidation behavior than ozone. Since, oxidation processes are energy intensive and expensive, their application is limited. Further, as oxidation processes are dependent on the stoichiometry, a large amount of oxygen is required for higher organic concentrations (Webber and Smith, 1986). Chlorine, chlorine dioxide, hypochlorite compounds are not used for oxidation due to their toxicity. (a) Hydrogen Peroxide Without an oxygen supplement, the oxidizing potential of hydrogen peroxide is insufficient to reduce the content of organic compounds, especially humic substances and facilitate degradation. However, hydrogen peroxide in the presence of a suitable catalyst, usually iron salts or UV-radiation (Steensen, 1997), can form hydroxyl radicals, which have a greater oxidation potential than hydrogen peroxide or ozone individually. According to Steensen (1993), the economic feasibility of adopting hydrogen peroxide as a chemical oxidation option is poor as 120 to 250 kWh/kg COD removed is required. 31
Page 1 and 2: APPLICATION OF MEMBRANE BIOREACTOR
Page 3 and 4: Abstract Landfill leachate is a com
Page 5 and 6: Table of Contents Chapter Title Pag
Page 7 and 8: 4.5.6 Cost Analysis for Operation 1
Page 9 and 10: 4.4 Effect of Free Ammonia Concentr
Page 11 and 12: 4.16 COD Concentration in the Influ
Page 13 and 14: MWCO Molecular Weight Cut-off MWW M
Page 15 and 16: 1.1 Background Chapter 1 Introducti
Page 17 and 18: generally unsuccessful in removal o
Page 19 and 20: 2.1 Introduction Chapter 2 Literatu
Page 21 and 22: In the municipal solid waste landfi
Page 23 and 24: COD/TOC, VS/FS and VFA/TOC ratios o
Page 25 and 26: Table 2.3 presents the general leac
Page 27 and 28: Ground water 2.7.1 Seasonal Variati
Page 29 and 30: Table 2.5 Variation of COD, BOD & B
Page 31 and 32: entails the re-circulation of leach
Page 33 and 34: Table 2.8 Summary of Biokinetic Coe
Page 35 and 36: that extensive loss of nitrogen (up
Page 37 and 38: ammonia could only be achieved when
Page 39 and 40: Table 2.10 Treatment Efficiencies o
Page 41 and 42: Activated Carbon Adsorption Granula
Page 43: Colloidal material as well as metal
Page 47 and 48: Ammonia Stripping Air stripping of
Page 49 and 50: These systems are land intensive wh
Page 51 and 52: the biological treatment can be rep
Page 53 and 54: Table 2.16 Typical Leachate Composi
Page 55 and 56: influent reached 200 mg/L. For the
Page 57 and 58: Table 2.18 Advantages and Disadvant
Page 59 and 60: through the effluent. Different ope
Page 61 and 62: Mixed Liquor Suspended Solids and D
Page 63 and 64: 2.12 Yeasts 2.12.1 Introduction The
Page 65 and 66: Nishihara ESRC Ltd. (2001) studied
Page 67 and 68: nitrification-denitrification proce
Page 69 and 70: Table 3.1 Composition of Simulated
Page 71 and 72: 3.4.1 Ammonia Toxicity The experime
Page 73 and 74: Figure 3.4 Experiments Conducted to
Page 75 and 76: Leachate Option Ammonia Stripping R
Page 77 and 78: MW larger than 50 kDa, (2) MW betwe
Page 79 and 80: Figure 3.7 Flowchart Showing Ammoni
Page 81 and 82: Chapter 4 Results and Discussion 4.
Page 83 and 84: COD Removal Effeciency (%) COD Remo
Page 85 and 86: MLSS (mg/L) 14000 12000 10000 8000
Page 87 and 88: Specific Growth Rate ( d -1 ) 0.50
Page 89 and 90: change in the predominant species w
Page 91 and 92: Table 4.4 Effect of Free Ammonia Co
Page 93 and 94: Table 4.5 Substrate Utilization by
Page 95 and 96:
4.3.1 Initial Membrane Resistance P
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when compared with the present stud
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COD Removal Efficiency (%) 90 80 70
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(2) TKN Removal Efficiency Prior to
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As there was no significant improve
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The probable reason for frequent fo
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Ammonia Concentration (mg/L) Ammoni
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concentration after treatment. Othe
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After the chemical cleaning of the
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emoval of 38%. A higher removal in
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Influent BOD (mg/L) Influent BOD (m
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(3) TKN Removal Efficiency The TKN
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Figure 4.34 gives the overall TKN r
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fraction and slowly biodegradable C
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BOD (mg/L) BOD (mg/L) 6000 5000 400
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Figure 4.39 Molecular Weight Cut-of
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COD (mg/L) 8000 6000 4000 2000 COD
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Though, the obtained COD removal ef
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cake used on the top of the membran
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Chapter 5 Conclusions and Recommend
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0.02, respectively. This can be con
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References Abeling, U., and Seyfrie
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Brown, M.J., and Lester, J.N., 1980
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Diamadopoulos, E., 1994. Characteri
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Grady, C.P.L., Daigger, G.T., and L
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Keenan, J.D., Steiner, R.L., and Fu
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Martin, G.M.A., Auzmenti, A.I., and
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Pohland, F.G., and Harper, S.R., 19
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Shin, H.S., An, H., Kang, S.T., Cho
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Visvanathan, C., Ben Aim, R., and P
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Appendix A Pictures of Experiments
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Raw Leachate YMBR Effluent BMBR Eff
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Appendix B Leachate Characteristics
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Table B-2 Acclimation of Mixed Yeas
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Appendix C Experimental Data of Bio
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y: Where: OUR at line g: This is th
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Table C-3 Experimental Results for
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Appendix D Membrane Resistance Stud
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Table D-3 Experimental Data for Det
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Table D-4 Experimental Data for Det
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Pressure (kPa) Pressure (kPa) 25 20
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Appendix E MBR without Ammonia Stri
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Day HRT (h) pH COD (mg/L) Feed Reac
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Day HRT (h) pH COD (mg/L) Feed Reac
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Table E-3 Variation in TMP with Tim
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Appendix F Ammonia Stripping Studie
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Table F-5 Pilot Scale Study on Ammo
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Table G-1 Feed, Reactor and Effluen
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Table G-3 Feed, Reactor and Effluen
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Appendix H Other Studies 179
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Table H-2 Membrane Resistance of th
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Table H-6 Chemical Cost for the Yea
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