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19/11/2011
1
Membrane Bioreactor (MBR) TechnologyHiren Trivedi‐OVIVO
List of Topics
• MBR Technology Overview
• MBR Design/Operation
• Nutrient Removal
• MBR Supplier Selection
• Case Studies
Conventional Wastewater Treatment
Screening &Grit Removal
Primary Settlement Secondary Treatment‘Biological’ Stage
SecondarySettlement
TreatedWater
Disinfection Sand Filtration
3mm ScreenMembrane
Reactor
Permeate(disinfected)
Membrane Bioreactor Process
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A membrane bioreactor is a state of the art wastewater treatment process utilising biological treatment alongside filtration all in one common tank.
What is a membrane bioreactor?
Membrane Bioreactor Process
How does it work ?
Filtration Process
Barrier filtration
Membranes
Separates solids and liquids
Biological Process
Activated sludge (MLSS)
Bacteria
Oxidises organic constituents, BOD, and Nitrification of Ammonia to Nitrate
Membrane + Bioreactor
Membrane Bioreactor Process
Membrane Type
Flat Sheet
•E.g. Kubota / Toray / Huber
•Generally more references
Hollow Fibre
•E.g. Zenon / Memcor / Puron
•Generally more flow
External Tubular
•E.g. Norit
•Newer applications in municipal field
8
Why Choose MBR Technology?
High Effluent Quality
Small Footprint
Process Stability and Flexibility
Expandability
Cost Effective?
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9
<0.05 NTU
ND Fecal Coliform
ND Total Coliform
>3‐log Virus Reduction
ND BOD
ND TSS
<3.0 mg/l TN
<0.03 mg/l TP
ND = Not Detectable by standard test methods.
Achievable Effluent Quality
0.001 0.01 0.1 1.0 10 100 1000
Bacteria
Coal dust Beach sand
Metal ions
Aqueous salts
m (log)
Relative Particle Sizes
Ultrafiltration
Virus
Microfiltration
SeparationProcess
Effective pore size
Nominal pore size
Cryptosporidia Giardia
Membrane Bioreactor Process
List of Topics
• MBR Technology Overview
• MBR Design/Operation
• Nutrient Removal
• MBR Supplier Selection
• Case Studies
Ovivo
Experienced MBR solution provider
•Over 350 MBR plants worldwide in operation or under construction in 5 continents
•Municipal and Industrial
•Licensee for Kubota, Japan
•UK and Ireland – Over 100 MBR plants operational
•US – Over 100 MBR plants operational
•India – Since last four years
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1313
Biological Process Design
Plant Hydraulics
Aeration Systems
Pre-TreatmentIntegration
& Controls
Operation &
Maintenance
Solids Handling
Equipment Selection
Biohydraulics
Membrane filtration and biological process design CANNOT be decoupled!
The Ovivo MBR SystemDesign Approach
Design Considerations ‐ Approach
Membrane Biomass
OperatingEnvironment
MBRConfiguration
Hydrophobicity
Porosity / Pore Size
MLSS (viscosity, zeta potential)
EPS (Extracellular polymeric substances)
Floc structure & MPS(Mean Particle Size)
Dissolved Material
Cross Flow Velocity
Aeration
TransMembrane Pressure
HRT/SRT
Typical MBR System Configuration The Submerged Membrane Unit (SMU)
Manifold
Membrane case
Membrane cartridge
Diffuser case
Diffuser
Tube
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1717
Hydraulics‐Pump Forward Designs
Cost of Added QVS
Reduce/Eliminate EQ Basin, Pump, Instr.
Reduce Site Footprint
Reduce Concrete Usage
Balance flows for Energy Optimization
Maintains Constant SWD in Aerated Basins
L
L
L
Gravity Return
Permeate
P
AX PA
Utilize
Percent of
Anoxic
Volume
MBR
18
Hydraulics‐Flow Splitting
Goal: Equal flows/solids through Trains & MBR basins
Avoid managing multiple processes
Avoid solids accumulation in MBRs (thickening)
Avoid localized dewatering
Common‐Wall Construction N+1 Construction
Q
AX
AX
AX
AX
PA
PA
PA
PA
MBR
MD
C
FD
C
MR
C
MBR
MBR
MBR
QP
AX
AX
AX
AX
PA
PA
PA
PA
MBR
MBR
MBR
MBR
SB
Q
Q
1919
Hydraulics‐Permeate Collection Methods
Gravity
P
Pumped
Pumping Energy to Convey Permeate
Low SWD
No Pumping Costs
High SWD
2020
Hydraulics‐Pump Assisted Gravity (PAG)
PAG is ~25% more energy efficient than gravity or pumped systems
• Lower blower discharge pressure
•Pumps only used to resolve air lock/high TMP
Clear Well
P
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2121
Biological‐T vs. SRT
T=10oC T=15oC T=20oC
Nitrification SRT 10 days 6 days 4 days
Denitrification SRT
7 days 4 days 3 days
Total SRT(No Safety Factor)
17 days 10 days 7 days
2222
Biological‐MBR Process Aeration
Keys:
1. Process Air Capacity and Turndown (Healthy Mixed Liquor/Good Filterability)
2. Scour Air Control (Membrane Biofilm Management)
Process Aeration:
Capacity for Peaks (peak load definitions)
Turndown for Low Loading (over aeration vs motor starts)
MBR Air Scour:
Peak capacity and turndown defined by Ovivo standards
Dependency on Constant MBR SWD
Biological‐Actual Energy Data, Dundee MI
0.00
0.50
1.00
1.50
2.00
2.50
3.00
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
Daily Flow (MGD)
En
erg
y C
on
sum
pti
on
(kW
h/m
3)
Avg. SBR Energy Usage 2001‐2005 (0.80kWh/m3)
Ovivo MBR Energy Usage
Actual Total Plant Energy Usage at Design AAF (1.5 MGD)
23
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Pumped System
Gravity System
Operational‐Measuring TMP
TMP = PS ‐ PP – PG
PG = PS ‐ PP ‐ TMP
PG
PS
PS
PG
TMP = Membrane & biofilm pressure losses
PP = Piping friction losses (fittings, piping, etc.)
PG = Gauge reading during filtration
PS = Static pressure reading at zero filtration
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Operational‐Chemical Cleaning (CIP)
Maintenance Cleaning
Intended to remove surface (biofilm or cake) fouling.1
Does not involve taking tanks out of service for extended periods of time (~1‐4hr)
Routine procedure
Can return to MBR filtration mode in ~15 minutes
Recovery Cleaning
• Intended to “dislodge particles from membrane microstructure.”1
• May take from >4‐24hrs.
• Requires that membranes be soaked in concentrated chemical solution.
• Generally a non‐routine procedure
1 Membrane Systems for Wastewater Treatment, WEF 2006.
0
10
20
30
40
50
60
4/8/2006 0:00 4/13/2006 0:00 4/18/2006 0:00 4/23/2006 0:00 4/28/2006 0:00 5/3/2006 0:00 5/8/2006 0:00
Per
mea
bilit
y (g
fd/p
si)
Maintenance Clean Efficiency
Target Perm. = 19 gfd/psi
CIP on April 22, 2006
Ovivo MBR System-Kubota Membranes
McFarland Creek, OH-6.8 MLD
2727
Standardized Automation
Overview
Train Status
Basin Status
Equip Status
Process Data
List of Topics
• MBR Technology Overview
• MBR Design/Operation
• Nutrient Removal
• MBR Supplier Selection
• Case Studies
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Nitrogen in wastewater
Raw wastewater contains nitrogen in the form of:
1. Organic Nitrogen2. Ammonia‐N (NH3‐N)3. Nitrate‐N (NO3‐N)4. Nitrite‐N (NO2‐N)
• TKN=1+2• TIN: 2+3+4• TN:1+2+3+4
Inert Nitrogen: 2% of TN
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Biological Nitrogen Removal
Two step process
•Nitrification (Pre‐Air and MBR basin)
•Denitrification (Anoxic basin)
Temperature dependent
30
31
Nitrification
• 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
32
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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3333
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
34
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
3636
•Optimized nitrification and denitrification reduces:
•Number of recycle streams + Recycle flowrate
•Low DO operation in the aeration zone significantly reduces aeration energy consumption
SNdNHRT=2 hr
MBRDO>1 ppm
HRT=2 hr
ANDO=0 ppm
HRT=1 hr
AXDO=0 ppm
HRT=1.5 hr
2-6 Q
1-2 QChemical
Post-AXDO=0 ppm
HRT=0.5 hr
Chemical
The UNRTM Process: 5‐stage Design
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Islamorada, Florida
350,000 gpd
4 Stage Process
Designed for AWT Standards
5/5/3TN/1TP limits
Injection Well Beneficial Reuse
38
Filtrate
WAS
PRAX SymBio PA MBR
Influent
POAX
Methanol
Plantation Key, Islamorada Biowin Model(UNR3TM Process)
Process Zone Abbreviation
Anaerobic AN
Pre-Anoxic PRAX
Pre-Aeration PA
Post-Anoxic POAX
Membrane MBR
Legend
RR1
RR2
3939
Original BioWin simulationFlow: 0.355 MGDBOD: 250 mg/LTSS: 250 mg/LTKN: 45 mg/L (BOD: TKN ratio: ~6:1)Methanol: 20 gpd (Estimated)CurrentFlow:0.035 MGDBOD: 170 mg/LTSS: 260 mg/LTKN: 69 mg/L (BOD: TKN ratio: ~2.5:1)Methanol: 2 gpd (Actual)Alum: 12 gpd for TP < 1
Plantation Key, FL: Nitrogen Removal
4040
Plantation Key, FL
Parameter CBOD TSS TN NO3 NH3 NO2 TKNTotalOrg.N TP
Limits 5 5 3 1
2007 (Avg.) 2.50 0.62 1.49 1.01 0.12 0.01 0.64 0.55 0.34
2008 (Avg.) 2.06 0.60 2.37 1.83 0.12 0.02 0.51 0.38 0.29
Parameter CBOD TSS TN NH3 TKN T Org.N TP
2007 (Avg.) 153.72 230.35 69.11 47.04 68.99 21.94 9.23
2008 (Avg.) 167.80 259.87 76.68 51.81 76.60 24.91 9.31
Influent
Effluent
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List of Topics
• MBR Technology Overview
• MBR Design/Operation
• Nutrient Removal
• MBR Supplier Selection
• Case Studies
List of Topics
MBR Supplier Selection Matrix
•Proven product? (History, Support)
•Cost of ownership? (Flux, Energy Optimization)
•Suitable for RO feed? (Reuse applications)
•Simple to use? (Cleaning and Maintenance)
•Operational flexibility? (MLSS variation, BNR)
MBR Selection‐Product History
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
Q&A