• Presence of oxygen• Occurs in Pre‐Air and MBR basins• Autotrophic bacteria are slow growing. Longer SRT needed• Nitrification consumes alkalinity @ 7.14 g alkalinity/g NH3‐N
Nitrification (NH3 to NO3) 4.57 gO2/gNH3
•Nitrosomonas•NH3 to NO2 3.43 gO2/gNH3
•Nitrobacter•NO2 to NO3 1.14 gO2/gNO2
•Electron Acceptor: Oxygen
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Denitrification
• Absence of free oxygen
• Occurs in Anoxic basin
• Heterotrophic bacteria
• Denitrification recovers 50% alkalinity lost in nitrification @ 3.57g alkalinity/g NO3‐N
Denitrification (NO3 to N2 gas)
• Alcaligens, Pseudomonas• NO3 to N2 2.86 gO2/gNO3
• Oxygen Equivalent of NO3
• Electron Acceptor: Nitrate
• BOD:TN ratio greater than or equal to 4
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Biological Nitrogen Removal
Need sufficient influent BOD/N ratio
•>4.0 for Level 1
•>6.0 for Level 2 & 3
Internal recycle – 2.0 to 4.0 (minimum)
DO in internal recycle consumes BOD in anoxic zone
•Can decrease denitrification rates
Sufficient SRT and DO needed for nitrification
•MBRs have less volume for higher SRTs (12 to 40 days)
•MLSS range 8,000 to 18,000 mg/L
NdN process issues same for MBR and Conventional A.S. processes
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Biological Phosphorus Removal ‐Release & Uptake
Absence of free oxygen Absence of Nitrate‐NPhosphorus Accumulating Bacteria (PAO)Release• Release in the Anaerobic basin – rbCOD is fermented to volatile fatty acids (VFA)
• PAO’s assimilate volatile fatty acids (VFA) and store them as Carbon products. During the process they release Orhtophosphate (O‐PO4)
• Retention time in Anaerobic basin: 0.5 to 1 hrUptake• Uptake in Aerobic and Anoxic Basin• PAO’s consume the stored carbon products and uptake phosphorus during the process.
Phosphorus is removed from wastewater by wasting sludge (PAO’s)Biological sludge w/o EBPR: <2% P by weightBiological sludge w EBPR: >4% P by weight
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Chemical Phosphorus Removal
Addition of Chemical
• Alum
• Ferric Chloride
Used for small plants and when low TP is required
Excess sludge generation
May require high metal:P ratio based on effluent quality
Effluent P conc. mg/L Al/P ratio
M/M
0.05 2.5
0.10 2.0
0.50 1.0
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•Optimized nitrification and denitrification reduces:
•Number of recycle streams + Recycle flowrate
•Low DO operation in the aeration zone significantly reduces aeration energy consumption
WWTPs are usually designed to last for 20‐30 years
Membrane life, warranty become a key selection criteria
Membrane suppliers should provide installation history for evaluation
End client, consulting engineers, EPC companies (Selectors) all have to evaluate:
• Risk to the stakeholders
• Cost of ownership
• After sale support
MBR Selection‐Design Flux
Design Flux selected has a direct impact on:• Quantity of membranes• Capital cost• O&M cost
• Aeration energy• Membrane replacement
Selectors should evaluate the flux values chosen by vendors in terms of: • Average (daily) sustainable flux/Max month flux• Peak daily flux• Peak instantaneous flux• Data from vendors to substantiate their claims
• Third party (independent) testing results
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MBR System‐RO Feed Quality Water
Tested Water
Water Temperature
(oC)Turbidity
(NTU) SDICODMn(mg/L)
MBR1 (SRT:300 days) 21.0 0.11 2.46 5.0
MBR 2 (SRT: 300 days) 18.0 0.10 2.66 4.3
MBR 3 (SRT: 120 days) 10.8 0.10 2.61 8.0
MBR 4 (SRT: 120 days) 11.0 0.10 0.40 8.3
MBR 5 (SRT: 120 days) 11.0 0.09 1.28 7.0
MBR 6 (SRT: 120 days) 11.0 0.10 2.60 8.5
MBR 7 (SRT: 10 days) 21.0 0.10 2.79 7.0
MBR 8 (SRT: 10 days) 17.5 0.10 2.28 9.3
MBR 9 (SRT: 2 days) 14.8 0.17 2.12 14.5
MBR 10 (SRT: 2 days) 13.0 0.17 2.75 26.3
Grey Water-1 23.0 0.12 2.19 2.2
Grey Water-2 22.5 0.11 1.96 2.6
Conventional WWTP 17.0 0.82 6.47 9
Tap Water 11.0 0.09 3.42 1
MBR System‐Kubota Membranes
Operational FlexibilityPermeate operation by:•Gravity•SuctionMLSS variation during operation:•8,000‐18,000 mg/L•Beyond 30,000 mg/L in thickening applicationsBiological Nutrient Removal (BNR)•Plants designed for TN, TP removal•Dynamic modeling of plant performance availableSimple screening requirement•3 mm perforated (punched) or 1‐2 mm bar screen•No need to screen RAS
List of Topics
• MBR Technology Overview
• MBR Design/Operation
• Nutrient Removal
• MBR Supplier Selection
• Case Studies
Case Studies
• DJB• GSK• Zydus Cadila• Godrej Tyson• MRPL
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Conclusions
•Increasing interest in the MBR technology for domestic wastewater treatment has occurred due to an increasing demand in water reuse and continuing advancement in membrane technology.
•The MBR process offers several benefits over the conventional activated sludge process, including: smaller space and reactor requirements, better superior solids removal, and disinfection.
•The effluent water quality from the MBR exceeds the quality of a conventional activated sludge system. THANK YOU
