Nutrient Removal Optimization at OECC - One Water …...BNR optimization • Leveraging existing...
Transcript of Nutrient Removal Optimization at OECC - One Water …...BNR optimization • Leveraging existing...
Nutrient Removal Optimization at OECCAlyssa Mayer, PEHazen and Sawyer
Presentation Overview
Project BackgroundBNR Design ConsiderationsProcess Model DevelopmentPreliminary Alternatives Evaluation ResultsConclusions and Next Steps
Olentangy Environmental Control Center (OECC)
North Plant (1.5 mgd) and South Plant (4.5 mgd)
Facility Plan is focused on:• Energy efficiency• BNR optimization• Leveraging existing infrastructure
Effluent Nutrient Limits MonthlyNH3-N (Winter), mg/L 1.28NH3-N (Summer), mg/L 0.78Total NOx-N, mg/L 4.58Total Phosphorus, mg/L 1.0
Process Modeling Task
Develop Process Model to:• Evaluate existing
biological treatment configuration
• Perform alternatives analysis for future improvements to meet nitrogen and phosphorus limits
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Meeting with plant staff and evaluation of historical data Detailed Sampling
wastewater characterization
ModelingBioWin Model Calibration
Alternatives Analysis
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Operational Considerations for EBPRAnaerobic
Zone Sizing
Carbon:TP
Limited DO, NO3 Return
DO Control
Effluent Solids Concentration
Anaerobic Zone
INFLUENT
RAS
Low DO
High DO or NO3-N
Size of Anaerobic Zone Effectively Reduced
Available Carbon for PAOs Reduced by OHOs
P-rich biomass
Low P effluent
Recycle Loading
Operational Considerations for Nitrogen Removal
NRCY
Anoxic Zone
DO Control
Aerobic SRT
NitrificationDenitrification
Temp/pH/AlkalinityCarbon:TN
Anoxic Conditions
Recycle Rate
Existing Aeration Tank Configuration
Aerated Operation70 minutes
Unaerated Operation50 minutes
Ferric
Historical Data Evaluation and Sampling Plan Development
Low Influent BOD and TSS measuredSludge production reflects more typical strength wastewaterConsistently meet effluent nutrient requirements with intermittent aeration operation and chemical additionAdditional sampling planned to verify influent, solids, BNR performance Sampling
Locations
Special Sampling Observations
• Influent CBODs for sampling week higher than historical average (~typical domestic)
• Influent sampler may underestimate solids (as compared with grab)
• Consistent sludge production at multiple points of measurement
• Very good biological phosphorus removal performance
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10
15
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StepFeed
13A 13B 14A 14B 15B MLSS Sec Eff
Nutrient Profile
NH3-N NO3 NO2 PO4-P
012345678
13 Z1 13 Z2 13 Z3 14 Z1 14 Z2 14 Z3 15 Z1 15 Z2 15 Z3
DO Profile
Aerobic Anoxic
Process Model Development
Influent Loading and
Characteristics
Intermittent Aeration
Operation
Ferric Addition
Aerobic Digester
Aeration and Decanting
Dewatering Schedule and
Capture
Good Match on Solids Production and Effluent Quality
Parameters units Measured Modeled % Difference Pass 3 MLSS mg/L 2,190 2,010 -8%WAS Load ppd 5,400 5,320 -1%Hauled sludge ppd 6,730 7,330 9%
Parameters units Measured Modeled % Difference Secondary Effluent TKN mg/L 2.0 1.96 -2%Secondary Effluent NH3 mg/L 0.6 0.58 -2%Secondary Effluent NOx-N mg/L 4.86 5.45 12%Secondary Effluent TP mg/L 0.12 0.14 --Secondary Effluent PO4-P mg/L 0.02 0.01 --
Modeled a Period of Time Outside Sampling Week
• Adjustment to the measured Influent CBOD, TSS necessary to match solids production and effluent quality.
• Historical data and modeling suggest variable EBPR performance over time
June – November 2017
Parameters units Jun - Nov 2017Measured Modeled
Sludge ProductionPass 3 MLSS mg/L 2,640 2,210WAS Load ppd 6,360 5,610Hauled sludge ppd 3,470 3,640EffluentFinal Effluent TSS mg/L 1.1 1.0Final Effluent cBOD mg/L 1.1 1.32Final Effluent TKN mg/L 1.1 1.52Final Effluent NH3 mg/L 0.13 0.38Final Effluent NOx-N mg/L 3.6 4.64Final Effluent TP mg/L 0.46 0.51
OECC Influent Design Criteria
Parameter Historical (2014-2017)
Projected
Annual Average Max Month “Build-out” Annual Average
Flow, mgd 3.3 6.0 7.7 12.0
Concentrations
Parameter Historical(2014-2017) Sample Week Low Strength High Strength
TSS, mg/L 119 167 112 209
cBOD, mg/L 69 187 125 234
TKN, mg/L - 34 23 43
NH3-N, mg/L 18 24 16 30
TP, mg/L 5.1 4.7 3.2 5.9
Preliminary Biological Process AlternativesTypical Nutrient Removal Performance
Configuration TN Removal Bio-P Removal
A/O(Anaerobic/Oxic) ○ ○ ○ ○ ○ ● ● ● ● ○MLE(Anoxic/Oxic) ● ● ● ○ ○ ○ ○ ○ ○ ○A2O(Anaerobic/Anoxic/Oxic) ● ● ● ○ ○ ● ● ● ○ ○4-Stage(Anoxic/Oxic/Anoxic/Oxic) ● ● ● ● ● ● ○ ○ ○ ○5-Stage(Anaerobic + 4-Stage) ● ● ● ● ○ ● ● ● ● ●
● Good Performance○ Poor Performance
“One OECC” Concept
Operate North and South Trains in Series as one process• Use North Volume for
Anaerobic (if 5 stage) and Anoxic
• Use South Volume for Aerobic, 2nd Anoxic and Reaeration
Future AA Alternatives Evaluation Results
ParameterMonthly Limits Low Strength Wastewater High Strength Wastewater
4-Stage 5-Stage 4-Stage 5-Stage
Final Effluent QualityFinal Effluent NH4-N, mg/L 0.78 / 1.28 0.08 0.08 0.08 0.07Final Effluent NOx-N, mg/L 4.58 1.7 2.9 3.1 4.2Final Effluent TP, mg/L 1.0 0.7 0.7 0.7 0.7Required Chemical AdditionFerric Addition, gpd -- 375 200 775 200Methanol Addition, gpd -- 0 0 0 80Solids ProductionTotal Sludge, ppd -- 4,300 3,900 8,700 7,600
Preliminary Conclusions and Next Steps
DCRSD can leverage existing infrastructure at OECC to meet future nutrient limits at future design flows and loads using a 4 or 5 stage BNR process Chemical coagulant will likely be required to meet TP limits, regardless of chosen process, some supplemental carbon may also be necessaryNext Steps:LCA including supplemental carbon, chemical coagulant, sludge disposal costs
Thank you!
Alyssa Mayer, [email protected]
Acknowledgements:OECC Operations StaffDCRSD Engineering StaffHazen Sampling Team