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

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Air Compressor Influent Air Diffuser Air Outlet Bio-Reactor Return Sludge Membrane Unit (a) (b) Figure 2.10 Schematic Diagrams of (a) External Recirculation MBR and (b) Submerged MBR System 2.11.1 Membrane Configuration Effluent Influent Membrane bioreactor configurations include: extractive membrane bioreactors (EMBR), bubble-less aeration membrane bioreactors (MABR), recycle membrane bioreactors and membrane separation bioreactors. Treatment by aerobic processes is often limited by insufficient oxygen while using air as an oxygen source. The implementation of oxygen as opposed to air as an aeration medium would increase the degradation rate of the system. However, since conventional aeration devices have high power requirements and a high rate of mixing, these devices cannot be used with biofilm processes. MABR process uses gas permeable membranes to directly supply high purity oxygen without bubble formation in a biofilm (Stephenson, et al., 2000). The membranes are generally configured in either a plate-and-frame or hollow fibre module. However, research has focussed on the hollow fibre arrangement with gas on the lumen-side and wastewater on the shell-side. The hollow fibre modules are preferred since the membrane provides a high surface area for oxygen transfer while occupying a small volume within the reactor. The membrane recycle bioreactor consists of a reaction vessel operated as a stirred tank reactor and a membrane module containing the membrane. The substrate and biocatalyst are added to the reaction vessel in pre-determined concentrations. Thereafter, the mixture is continuously pumped through the membrane. While the biocatalyst adheres to the membrane surface, the medium permeates through the membrane and is recycled to the reactor vessel. A summary of the advantages and disadvantages of each bioreactor configuration is presented in Table 2.18. The versatility and treatment capability of membrane bioreactors has catapulted the technology as a viable alternative in water and wastewater treatment over a short period. Initial design configurations of external loop systems were prone to fouling which prevented stable operation and hence was confined to small-scale operations with limited value and applicability. 42 Feed Tank Compressed Air Effluent Level Control Tank Membrane Air Diffuser
Table 2.18 Advantages and Disadvantages of Membrane Bioreactors (Stephenson, et al., 2000) Advantages Disadvantages Membrane Separation Bioreactors Small footprint Complete solids removal from effluent Effluent disinfection Combined COD, solids and nutrient removal in a single unit High loading rate capacity Low/zero sludge production Rapid start up Sludge bulking not a problem Modular/ retrofit Membrane Aeration Bioreactors High oxygen utilization Highly efficient energy utilization Small footprint Feed-forward control of O demand Modular/retrofit Extractive Membrane Bioreactors Treatment of toxic industrial effluent Small effluent Modular/retrofit Isolation of bacteria from wastewater 43 Aeration limitations Membrane fouling Membrane costs Susceptible to membrane fouling High capital costs Unproven at full-scale Process complexity High capital cost Unproven at full-scale Process complexity Systems were designed with long HRT and SRT resulting in little or no sludge production. The basic problem with membrane bioreactor technology in the early development stages was the high energy costs and the high cost of membranes. Application was therefore limited to small industrial and commercial systems that used large diameter membranes with little pre-screening and could handle large concentrations of solids in the mixed liquor typically of 20,000 to 40,000 mg/L. The membrane bioreactor was revolutionised when focus shifted to immersed membrane bioreactor systems. The membrane was immersed directly into the activated sludge tank with constant flow maintained by an upstream level control tank. The system SRT was maintained, however, MLSS concentrations were lowered to 15,000 from 25,000 mg/L. The evolutions away from the external circuit reduced energy consumption and broaden the membrane scope to large-scale varied applications. However, as cited in McCann (2002), the membrane costs were high; fluxes were low and a standardised operating protocol incorporating flux enhancement and chemical cleaning was not established. Later, large-scale systems were developed and optimization for municipal wastewater treatment. The MLSS was further lowered to 15,000 from 20,000 mg/L while the SRT remained long to limit sludge production. Developments in the optimization of operating conditions has allowed for prolonging membrane life to approximately 5 years. Process developments included 3-mm pre-screening, increase in membrane and plant size,
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APPLICATION OF MEMBRANE BIOREACTOR
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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 and 44: Colloidal material as well as metal
Page 45 and 46: iologically, physical-chemical proc
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: influent reached 200 mg/L. For the
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
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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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Thesis - faculty.ait.ac.th - Asian Institute of Technology

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