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

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Table 4.8 TKN Removal Efficiency in YMBR System HRT (h) 24 TKN Removal (%) 20 16 12 Maximum 28 20 36 23 Minimum 28 18 15 11 Average 28 19 29 18 Std. Dev. 0 1 7 5 Table 4.9 TKN Removal Efficiency in BMBR System HRT (h) 24 TKN Removal (%) 20 16 12 Maximum 26 35 35 19 Minimum 24 13 15 10 Average 25 22 25 14 Std. Dev 1 10 6 3 Along with TKN Removal, the total ammonium content was also measured. The influent ammonium concentration was around 1,700 mg/L. The ammoniacal nitrogen contributed to about 85% and above of the total organic nitrogen. The effluent ammonium concentration in the YMBR and BMBR systems was 1,235 and 1,285 mg/L, respectively. The ammonium removal concentration was also found to be very low with 18% and 20% in the BMBR and YMBR system, respectively. The ammonium concentration contributed to 85-90% of the total nitrogen. The nitrite and nitrate concentrations (NO2 - and NO3 - ) in both YMBR and BMBR effluents were found to be very low. NO2 - and NO3 - concentration in the YMBR and BMBR effluent ranged from 0.8 to 6.4 mg/L and less than 1.0 mg/L, respectively. The probable reason for the absence of a notable range of nitrate and nitrite could be due to the absence of nitrifying bacteria, namely the Nitrosomonas and Nitrobacter. The inhibition of Nitrosomonas could be due to the free ammonia present in leachate as suggested by many researchers, that around 7 to 150 mg/L would affect the Nitrosomonas and a concentration of around 0.1 to 1.0 mg/L would affect the Nitrobacter (Barnesand and Bliss, 1983; Abeling and Seyfried, 1992). This would have therefore affected the nitrification process, as a result of which, the leachate should be pre-treated to reduce ammonia concentration. Along with the nitrogen content, the phosphorus content in the leachate was also measured. The average phosphorus concentration found in the leachate was 68 mg/L. The COD: P ratio was also calculated to find out the nutrient deficiency in the leachate. The COD: P ratio in the leachate was 100:0.85. Though, the leachate was said to be marginally phosphorus deficient, it did not adversely affect the COD removal efficiency in the MBR systems. This was tested with and without addition of polyphosphate in the treatment system. Further, many biological treatment systems have been used for treating leachate even with a COD:P as low as 100.02 (Pohland and Harper, 1985). The phosphate removal in both the reactors was approximately 50%. During the operation of membrane bioreactors, a frequent problem faced was foaming. Antifoam addition was used to prevent foam development (Praet, et al., 2001). 88
As there was no significant improvement when the HRT was increased from 16 to 24 h in terms of COD removal, further investigations were done at these two HRT, with 16 h HRT followed by 24 h HRT. 4.3.3 Membrane Fouling and Membrane Resistance The membrane fouling is the result of accumulation of rejected particles on the top of the membrane (external fouling), or deposition and adsorption of small particles or macromolecules at the pores or within the internal pore structure (internal fouling) of the membrane (Guell, et al., 1999). The processes that contribute to the fouling are varied. They include adhesion of the colloidal matters and macromolecules on the external and internal surface, growth and adhesion of biofilms on the membrane surface, precipitation of solved matters, aging of the membrane, etc (Gunder, 2001). Because of the complex and diverse relationships, it is not possible to localize and define fouling clearly. The adverse effects of the membrane fouling is the reduction of the permeate flux. In the present study, a constant flux was maintained in the membrane bioreactors. The resistance of the membrane influences the permeate flux. To maintain a constant flux, the flow rate was increased correspondingly by adjusting the suction pump. The rapid membrane fouling is indicated by a sudden increase in the transmembrane pressure. As a high transmembrane pressure is a result of the membrane fouling process, it was used as a parameter indicating requirement of cleaning. The membrane in the membrane reactors were cleaned when the transmembrane pressure difference increased significantly. The membranes were cleaned before it reached the maximum pressure to prevent damage to the membrane operation. The transmembrane pressure difference of the YMBR and BMBR systems is given in Figure 4.20. The detailed results are given in Table E-3 and E-4 of Appendix E. Though the two reactors, with bacterial and yeast culture did not show much difference in the performance, the yeast reactor showed an added advantage of lower membrane fouling and thus, longer membrane life. The cleaning was done by first flushing the membrane with tap water to remove the cake layer from the membrane surface. Later, a 3% sodium hydroxide solution was filtered through the membrane and then, washed with tap water. Finally, 1% solution of nitric acid was filtered through the membrane followed by tap water. This cycle was repeated until the membrane resistance was almost equal to the initial membrane resistance. The frequency of cleaning was greater in bacterial membrane bioreactor than the yeast membrane bioreactor. The frequency of membrane fouling is presented in the Table 4.10 for both the systems. The membrane resistance after cleaning is presented in Table 4.11. The detailed calculation is summarized in Table D-3 and D-4 and Figure D-1 and D- 2 of Appendix D. The bacterial system was first cleaned after 63 days of operation while the yeast based system was cleaned after 80 days. It could be said that the membrane with yeast reactor could be operated 27% more than the bacterial system. Further, in a total of 181 days of operation of the MBR systems, the BMBR was cleaned five times compared to three times in the YMBR system. The operating time of the yeast membrane was about 1.3 times longer than the bacteria membrane. 89
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APPLICATION OF MEMBRANE BIOREACTOR
Page 3 and 4:
Abstract Landfill leachate is a com
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Table of Contents Chapter Title Pag
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4.5.6 Cost Analysis for Operation 1
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4.4 Effect of Free Ammonia Concentr
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4.16 COD Concentration in the Influ
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MWCO Molecular Weight Cut-off MWW M
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1.1 Background Chapter 1 Introducti
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generally unsuccessful in removal o
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2.1 Introduction Chapter 2 Literatu
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In the municipal solid waste landfi
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COD/TOC, VS/FS and VFA/TOC ratios o
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Table 2.3 presents the general leac
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Ground water 2.7.1 Seasonal Variati
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Table 2.5 Variation of COD, BOD & B
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entails the re-circulation of leach
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Table 2.8 Summary of Biokinetic Coe
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that extensive loss of nitrogen (up
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ammonia could only be achieved when
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Table 2.10 Treatment Efficiencies o
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Activated Carbon Adsorption Granula
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Colloidal material as well as metal
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iologically, physical-chemical proc
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Ammonia Stripping Air stripping of
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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
Page 97 and 98: when compared with the present stud
Page 99 and 100: COD Removal Efficiency (%) 90 80 70
Page 101: (2) TKN Removal Efficiency Prior to
Page 105 and 106: The probable reason for frequent fo
Page 107 and 108: Ammonia Concentration (mg/L) Ammoni
Page 109 and 110: concentration after treatment. Othe
Page 111 and 112: After the chemical cleaning of the
Page 113 and 114: emoval of 38%. A higher removal in
Page 115 and 116: Influent BOD (mg/L) Influent BOD (m
Page 117 and 118: (3) TKN Removal Efficiency The TKN
Page 119 and 120: Figure 4.34 gives the overall TKN r
Page 121 and 122: fraction and slowly biodegradable C
Page 123 and 124: BOD (mg/L) BOD (mg/L) 6000 5000 400
Page 125 and 126: Figure 4.39 Molecular Weight Cut-of
Page 127 and 128: COD (mg/L) 8000 6000 4000 2000 COD
Page 129 and 130: Though, the obtained COD removal ef
Page 131 and 132: cake used on the top of the membran
Page 133 and 134: Chapter 5 Conclusions and Recommend
Page 135 and 136: 0.02, respectively. This can be con
Page 137 and 138: References Abeling, U., and Seyfrie
Page 139 and 140: Brown, M.J., and Lester, J.N., 1980
Page 141 and 142: Diamadopoulos, E., 1994. Characteri
Page 143 and 144: Grady, C.P.L., Daigger, G.T., and L
Page 145 and 146: Keenan, J.D., Steiner, R.L., and Fu
Page 147 and 148: Martin, G.M.A., Auzmenti, A.I., and
Page 149 and 150: Pohland, F.G., and Harper, S.R., 19
Page 151 and 152: 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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