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

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Table 4.12 Variation in Ammonia Removal Efficiency Velocity Gradient (s Ammonia Removal (%) Contact Time (h) -1 ) 2 4 6 0 28-31 37-46 47-51 1,530 61-66 84-86 88-93 2,850 69-74 88-95 96-98 4,330 71-76 89-95 96-98 While Diamadopoulos, 1994 did the ammonia removal experiments using air stripping at pH 11.5 with air flow rate 2-3.5 L air/L in leachate, he could achieve 95% ammonia removal after a time period of 24 h. The removal efficiency of air stripping was similar with the present study, with the advantage that the present study required a lower time period. The main role of agitation was to create turbulence sufficient enough in the free leachate surface, to increase the surface area for ammonia removal (Smith and Arab, 1988). In this case, the ammonia desorption would be less important than the surface area similar to studies done by Cheung, et al. (1997). This could be the probable reason for the efficient removal at a lower contact time. Another added advantage is that the present process can withstand changes in the volume and leachate concentration in comparison with the nitrification and denitrification processes for ammonia removal. It could also be said that ammonia stripping is an appropriate option for pre-treatment of leachate even in terms of cost-effectiveness (Cheung, et al., 1997). In the second stage of ammonia stripping studies as mentioned above, the pilot-scale studies were done to confirm the results obtained from laboratory-scale studies. The pilot scale study was conducted with leachate volume of 40 L at pH 11-12 and velocity gradient of 2,850 s -1 . The summary of the pilot scale studies are given in Table F-5 of Appendix F. The contact time was varied from 1 to 5 h. At each hour, the removal efficiency was measured. The average removal efficiency was found to be 89% at 5 h contact time. From the pilot scale studies, similar removal efficiency was expected at 4 h. Pilot scale results could be taken as a representative results as the standard error decreased with increasing volume. When Yangin, et al. (2002) worked on ammonia stripping of domestic wastewater mixed with leachate, it was found that 89% ammonia could be removed from the UASBR effluent containing an ammonium concentration of 1,000-2,000 mg/L. So, with the pilot scale study, we can be assured that the optimum condition persists at 5 h contact time. To verify this result again, with varying leachate ammonia concentration, the experiment was conducted and the average ammonia removal efficiency of 86% could be obtained with standard deviation of 3 mg/L. The results of this experiment are given in Table F-6 of Appendix F. The mechanism in ammonia stripping could be due to the ammonia desorption from the surface of the liquid leachate into the gaseous phase. It has also been said that the mass transfer of ammonia from liquid to air is proportional to the concentration of ammoniacal nitrogen in the solution and is a first order reaction (Srinath and Loehr, 1974). However, this could not be proved significantly in the present study, as only a range of ammoniacal nitrogen in the leachate was used in the experiment. Another aspect to be discussed in the study would be biological removal of ammonia in the aeration process through agitation. It was clear that the ammonia was removed through stripping rather than biological activity as there wasn’t a significant increase in the concentration of the oxidized nitrogen 94
concentration after treatment. Other probable reasons could be absence of the nitrification process at a pH as high as 11 which would rather inhibit the process regardless of the composition of leachate used, absence of sufficient nitrifying bacterial population and oxidation of ammonia would require long generation time (Cheung, et al., 1997). 4.4.2 Membrane Resistance and Membrane Cleaning The experiment on ammonia coupled membrane bioreactor for leachate treatment was continued with the membranes which were used for the previous set of experiments. A new membrane was changed in both the bioreactors after few days of operation. The membrane was changed after 45 days in the BMBR system and after 204 days in the YMBR system. The data and figure for initial membrane resistance measurement are given in Table D-5 and Figure D-3 of Appendix D. The membrane resistance of the new membrane used in the BMBR system was found to be 7.07 x 10 11 m -1 and that of YMBR was found to be 9.75 x 10 11 m -1 . The frequency of cleaning in the BMBR system was twice, 114 and 174 days after the experiment started. It was found that the yeast system operated 2.5 times more than that of the bacterial system. Membrane fouling causing a decline of permeate flux can also be explained using the resistance-in-series model, which provides a simplistic means to describe the relationship between permeate flux and trans-membrane pressure. As described in this model, the permeate flux is given by the Equation 4.2 and total resistance is given by Equation 4.3. Where; Rt = Rm + Rn + Rc Eq. 4.3 Rm = intrinsic resistance (m -1 ) Rn = irreversible fouling (m -1 ) = resistance due to cake layer (m -1 ) Rc This equation gives the various parameters that affect the filtration performance. Irreversible fouling (Rn) results in supplementary resistance to filtration and is often due to adsorption of soluble organics. Resistance due to the cake that forms on the membrane surface (Rc) is a function of the concentration and composition of suspended matters as well as the applied hydraulic conditions. The total resistance (Rt) was measured immediately after the clogging of the membrane. Rm and Rn were obtained by measuring the resistance of the membrane after being washed with tap water to remove the cake layer. The membrane resistance after chemical cleaning before the operation was considered as Rm. Rc Value was derived from Rt, Rm, and Rn using Equation 4.3. To have a better understanding of the membrane resistance and its role in biofouling, the membrane resistance caused by the varied factors was measured while cleaning the membrane in the BMBR system. The varied resistance measured during the first and the second cleaning is presented in Table 4.13. 95
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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
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the biological treatment can be rep
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Table 2.16 Typical Leachate Composi
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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 and 102: (2) TKN Removal Efficiency Prior to
Page 103 and 104: As there was no significant improve
Page 105 and 106: The probable reason for frequent fo
Page 107: Ammonia Concentration (mg/L) Ammoni
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
Page 153 and 154: Visvanathan, C., Ben Aim, R., and P
Page 155 and 156: Appendix A Pictures of Experiments
Page 157 and 158: 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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