Nutrient Removal Optimization at the Fairview WWTP

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1 Alyssa Mayer, PE Principal Engineer Nutrient Removal Optimization at the Fairview WWTP Mark Strahota, PE Associate

2 Presentation Overview Project Background Process Model Development BNR Design Considerations Alternatives Evaluation Results Recommendations

3 Water Authority of Dickson County Fairview WWTP Two channel oxidation ditch retrofit for biological nutrient removal 0.46 MGD Permitted Capacity (Currently receiving 0.3 MGD) Seasonal Nutrient Limits TN = 5 mg/l TP = 0.5 mg/l Antidegradation Study

4 Project Scope Develop calibrated BioWin model to evaluate: 1) Improvements to optimize current facility to meet existing rated capacity (0.46 mgd) 2) Identify and evaluate alternatives to expand the facility to 0.75 mgd in the future Scenario Flow (mgd) CBOD (mg/l) Effluent Concentration Limit NH3-N (mg/l) TN (mg/l) TP (mg/l) Permit Future

ML TO CLARIFIERS RAS NO-PHOS FEED Internal

5 Oxidation Ditch Configuration Current Aerobic Mechanical aerators supply required oxygen to a very small footprint High DO near aerators, anoxic conditions downstream ML TO CLARIFIERS RAS NO-PHOS FEED Internal Recycle Anoxic/ Anaerobic INFLUENT Surface Aerators, Typ

6 Process Model Development

Process Model Data Requirements Process Inputs: Wastewater Characteristics Loadings Dynamic Patterns Process Model Variables: Biological Reactions Physical/Chemical Effluent Quality Influent

7 Process Model Data Requirements Process Inputs: Wastewater Characteristics Loadings Dynamic Patterns Process Model Variables: Biological Reactions Physical/Chemical Effluent Quality Influent Anaerobic Zone Anoxic Zone Aerobic Zone Clarifier Required Air Process Configuration: Flow Routing Unit Sizes Reactor Staging Recycle Streams Process Operating Conditions: Recycle Rates DO Control Setpoints Solids Production WERF Methods of Wastewater Characterization for Activated Sludge Modeling (2003)

8 Levels of Model Calibration Level 1 Default Parameters and Assumptions No site specific information collected. Model defaults or assumptions used for all inputs Level 2 Historical Data Recorded plant historical data used as the basis for developing model inputs with limited additional sampling to verify influent characteristics. Level 3 Full-scale Testing Detailed sampling to characterize influent wastewater and process performance. Dynamic performance also characterized. Level 4 Direct Parameter Measurement Bench scale testing also performed to directly measure site specific kinetic parameters

9 Historical Data Review Parameter Influent Concentrations (AA) Effluent Concentrations (AA) Flow, mgd CBOD5, mg/l TSS, mg/l NH 3 -N, mg/l TN TP

10 Sampling Plan Characterize influent wastewater Confirm sludge production Confirm operating conditions and nitrogen removal performance in oxidation ditch Composite Grab

11 Developed Influent Characteristics and other model inputs based on special sampling data Chemical Addition WAS Flows DO Profiles Influent Characteristics

12 Model Calibration Results Parameters Special Sampling Period Measured Modeled BioWin Effluent TSS, mg/l TKN, mg/l Effluent NH 3, mg/l Nitrate+Nitrite, mg/l Effluent TP, mg/l Effluent TN, mg/l Solids Production MLSS 3,505 3,646 RAS Flow RAS concentration 7,207 7,433 Hauled sludge, ppd

13 Design Considerations for BNR

14 Enhanced Biological Phosphorus Removal 14

15 Conventional EBPR Configuration Low P effluent P-rich biomass

Limited DO, NO3 Return Anaerobic Zone Size of Anaerobic Zone

16 Operational Considerations for EBPR Carbon:TP Anaerobic Zone Sizing Effluent Solids Concentration DO Control Low DO INFLUENT RAS Limited DO, NO3 Return Anaerobic Zone Size of Anaerobic Zone Effectively Reduced High DO or NO 3 -N Available Carbon for PAOs Reduced by OHOs

17 Biological Nitrogen Removal Nitrification Denitrification Aerobic Anoxic

18 Example Nitrogen Removal Configuration NRCY Anoxic Zone

19 Operational Considerations for Nitrogen Removal Recycle Rate NRCY Carbon:TN ph/alkalinity Anoxic Zone DO Control Anoxic Conditions Aerobic SRT Nitrification Denitrification

20 Simultaneous Nitrification and Denitrification (SND) Possible to accomplish Nitrification and Denitrification in the same reactor volume Aerobic Partial nitrification (NH 3 to NO 3 /NO 2 ) Create an oxygen gradient within the floc Common in oxidation ditches Anoxic Denitrification (NO 3 /NO 2 to N 2 ) 20

21 BioWin Model Results

22 Model Predicted Effluent at 0.46 mgd in Current Configuration ML TO CLARIFIERS RAS NO-PHOS FEED (20 GPD) Ammonia N [mgn/l] Nitrate N [mgn/l] Internal Recycle Nitrite N [mgn/l] Soluble PO4-P [mgp/l] INFLUENT Surface Aerators, Typ 0 Influent Outer 1 Outer 3 Outer 5 Inner 1 Inner 3 Final Clarifier 2 Flow Eff. TN Eff. TP 0.46 MGD 7.7 mg/l 0.3 mg/l Effluent

23 Challenges Identified 0.46 mgd Annual Average Flow Insufficient aeration capacity for the oxidation ditch to maintain nitrification during cold weather Insufficient influent carbon to achieve total nitrogen (TN) removal to 5.0 mg/l. Limited operability and capacity at headworks

24 Fairview WWTP Modeled Improvements Phase 1 Annual Average Flow (0.46 MGD) ML TO CLARIFIERS NO-PHOS FEED (Polishing) Separation walls and baffle walls compartmentalized treatment improves biomass conditioning Remove Discs on one of aerators in outer pass Internal Recycle Glycerol Feed 30 gpd INFLUENT ANAEROBIC RAS Blowers and fine bubble diffusers add treatment capacity and efficiency Relocate RAS discharge improves biomass conditioning (settling and bio-p performance) Relocate internal recycle pumping improves performance and reduces glycerol usage Relocate No-Phos feed allows bio- P and improve efficiency Glycerol (supplemental carbon) feed facilitates denitrification

25 Fairview WWTP Model Results Phase 1 Annual Average Flow (0.46 MGD) ML TO CLARIFIERS NO-PHOS FEED (Polishing) 45 Temp = 18.7 C Ammonia N [mgn/l] Nitrite N [mgn/l] Nitrate N [mgn/l] Soluble PO4-P [mgp/l] Internal Recycle 10 5 ANAEROBIC RAS 0 Influent Outer 1 Outer 3 Outer 5 Inner 1 Inner 3 Final Clarifier 2 Effluent Glycerol Feed 30 gpd INFLUENT Flow Eff. TN Eff. TP 0.46 MGD 5.0 mg/l 0.5 mg/l

Fairview WWTP Model Results Phase 2 Annual Average Flow (0.75 MGD) Addition Aeration Needed ML TO CLARIFIERS NO-PHOS FEED (Polishing) 45 40 35 Temp = 18.

26 Fairview WWTP Model Results Phase 2 Annual Average Flow (0.75 MGD) Addition Aeration Needed ML TO CLARIFIERS NO-PHOS FEED (Polishing) Temp = 18.7 C Ammonia N [mgn/l] Nitrite N [mgn/l] Nitrate N [mgn/l] Soluble PO4-P [mgp/l] Internal Recycle 10 5 ANAEROBIC RAS 0 Influent Outer 1 Outer 3 Outer 5 Inner 1 Inner 3 Final Clarifier 2 Effluent Glycerol Feed 30 gpd INFLUENT Flow Eff. TN Eff. TP 0.75 MGD 3.0 mg/l 0.3 mg/l

27 Fairview WWTP Winter Operation Phase 2 Annual Average Flow (0.75 MGD) ML TO CLARIFIERS NO-PHOS FEED (Polishing) Temp = 12 C Ammonia N [mgn/l] Nitrite N [mgn/l] Nitrate N [mgn/l] Soluble PO4-P [mgp/l] Internal Recycle 10 5 ANAEROBIC RAS 0 Influent Outer 1 Outer 3 Outer 5 Inner 1 Inner 3 Final Clarifier 2 Effluent Glycerol Feed 100 gpd INFLUENT Flow Eff. TN Eff. TP 0.75 MGD 4.5 mg/l 0.3 mg/l

28 So we have a plan for retrofit, but Where are we going to send the wastewater while we retrofit the existing oxidation ditch? What happens if the oxidation ditch needs to be drained for maintenance in the future? Redundancy recommended in a phased approach

29 Recommendations

30 Phase 1 Improvements: 0.46 MGD, Eff. TN = 5 mg/l, TP = 0.5 mg/l Additional Aeration Discs in Existing Oxidation Ditch New Supplemental Carbon Feed Facility Headworks Expansion

31 Phase 1 Improvements ML TO CLARIFIERS RAS NO-PHOS FEED Ammonia N [mgn/l] Nitrite N [mgn/l] Nitrate N [mgn/l] Soluble PO4-P [mgp/l] 30 Internal Recycle Leave disc aerators in place; move and add discs to O1, O3, and O7 Glycerol (supplemental carbon) feed facilitates denitrification Relocate No-Phos feed improve efficiency of chemical precip 0 Influent Outer 1 Outer 3 Outer 5 Inner 1 Inner 3 Final Clarifier 2 Effluent Glycerol Feed INFLUENT Flow Eff. TN Eff. TP 0.46 MGD 5.0 mg/l 0.5 mg/l

32 Phase 2 Improvements: 0.75 MGD, Eff. TN = 3 mg/l, TP = 0.3 mg/l New 3 rd Clarifier Disinfection Expansion New Blower Building New 2 nd Process Train

33 Acknowledgements Water Authority of Dickson County Michael Adams, PE Michael Rogers, PE Rocky Bowker Carl Fuqua Hazen and Sawyer Nashville Scott Woodard, PE Saya Ann Qualls, PE Robert Warden, PE

Alyssa Mayer, PE 513-469-5135 amayer@hazenandsawyer.

34 Alyssa Mayer, PE Saya Qualls, PE Mark Strahota, PE Scott Woodard, PE

35 Bullpen Slides

37 Antidegradation Study Tennessee Requirements Applicants must demonstrate either that the discharge will meet water quality standards and either: be de minimis be necessary to accommodate social and economic development Tennessee requires development of a calibrated water quality model to determine level of degradation Calibration data being collected during summer 2017

38 Nitrification in Winter Slower growth of nitrifying organisms in cold weather Primary goal is to maintain nitrifier population for quick recovery in warmer weather Sufficient aerobic solids retention time (asrt) critical Minimum Aerobic SRT (days) Temperature ( o C)

39 Phase 1 Improvements Item *OPCC = Opinion of Probable Construction Cost, AACE Level 4 (Conceptual). Includes 30% Design Contingency and accuracy range of -30% to +50% All costs in 2016 Dollars (no escalation included) Cost General Requirements $130,000 Supplemental Carbon Feed Facility $280,000 New Orbal Equipment $430,000 Headworks Expansion $800,000 Mobilization, Bonds & Ins, OH & P $380,000 Design Contingency (30%) $600,000 Total OPCC* $2,620,000

40 Phase 2 Improvements Item *OPCC = Opinion of Probable Construction Cost, AACE Level 4 (Conceptual). Includes 30% Design Contingency and accuracy range of -30% to +50% All costs in 2016 Dollars (no escalation included) Cost General Requirements $250,000 Blower Building $600,000 2 nd Process Train $1,330,000 3 rd Clarifier $700,000 Mobilization, Bonds & Ins, OH & P $650,000 Design Contingency (30%) $1,050,000 Total OPCC* $4,580,000

41 Increases in O&M Costs $160, $140,000 $120, Increase in O&M Costs $100,000 $80,000 $60,000 $40,000 O&M cost increase for 0.46 MGD annual average flow (primarily supplemental carbon) Significant chemical addition for LOT nutrient removal (costs shown for 0.75 MGD flow) Flow (MGD) $20,000 $ Power Sludge Hauling Chemical Feed Equipment Maintenance Permitted Capacity

42 Basis for O&M Calculations All costs in 2016 dollars 3.1% nominal discount rate per OMB Circular A-94 Current power cost = $0.076/KWH Hourly rate for labor = $27.50 Sludge hauling = $1.75/mi Coagulant (No-Phos) = $1.85/gal Supplemental carbon (glycerol) = $2.25/gal Hypochlorite = $0.85/gal Equipment maintenance = 2% of capital cost

43 BNR/ENR Limits of Technology To go below 3 mg/l TN and 0.3 mg/l TP (objective for 1 MGD), further analysis is required May be possible with 5-stage ENR process May require tertiary treatment, for example: Tertiary filters remove TP and TSS Denitrification filters remove nitrate (TN) Ballasted flocculation remove TP and TSS Membrane bioreactors (MBR) remove TN, TP and TSS All can be costly May not be feasible

44 Reliability Enhancements Aeration Basins Swing zones Ability to return from WAS storage? Step feed Clarifiers Both in service: Capacity is insufficient at 1 MGD with 3500 mg/l MLSS (with current settling characteristics), and borderline at 0.75 MGD with 3500 mg/l MLSS Recommend a third clarifier

45 Fairview WWTP Proposed Configuration Phase 2 Max Month Flow (1.0 MGD) ML TO CLARIFIERS NO-PHOS FEED (100 gpd) Temp = 18.7 C Ammonia N [mgn/l] Nitrite N [mgn/l] Nitrate N [mgn/l] Soluble PO4-P [mgp/l] Internal Recycle 10 5 ANAEROBIC RAS 0 Influent Outer 1 Outer 3 Outer 5 Inner 1 Inner 3 Final Clarifier 2 Effluent Glycerol Feed 120 gpd INFLUENT Flow Eff. TN Eff. TP 1.0 MGD 3.0 mg/l 0.3 mg/l

46 Glycerol Feed 120 gpd Fairview WWTP Winter Operation Phase 2 Maximum Month Flow(1.0 MGD) ML TO CLARIFIERS NO-PHOS FEED (Polishing) Temp = 12 C Ammonia N [mgn/l] Nitrite N [mgn/l] Nitrate N [mgn/l] Soluble PO4-P [mgp/l] Internal Recycle 10 5 INFLUENT ANAEROBIC RAS 0 Influent Outer 1 Outer 3 Outer 5 Inner 1 Inner 3 Final Clarifier 2 Flow Eff. TN Eff. TP 1.0 MGD 9.1 mg/l 0.1 mg/l Effluent

Simultaneous Nutrient Removal: Quantification, Design, and Operation. Leon Downing, Ph.D., PE Donohue & Associates

Simultaneous Nutrient Removal: Quantification, Design, and Operation Leon Downing, Ph.D., PE Donohue & Associates Simultaneous Nutrient Removal Simultaneous nitrification, denitrification, and potentially