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Sustainable Supplemental Carbon Sources

93 rd Annual Fall Conference. Embassy Suites Charlotte | Concord, NC | November 10-13 | 2013. Sustainable Supplemental Carbon Sources. Hunter Long 1 , Katya Bilyk 1 , Wendell Khunjar 1 Jeff Nicholson 2 , Bill Balzer 2 , Charles Bott 2 James Grandstaff 3 Steven Chiesa 4 Jared Alder 5

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Sustainable Supplemental Carbon Sources

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  1. 93rd Annual Fall Conference Embassy Suites Charlotte | Concord, NC | November 10-13 | 2013 • Sustainable Supplemental Carbon Sources • Hunter Long1, Katya Bilyk1, Wendell Khunjar1 • Jeff Nicholson2, Bill Balzer2, Charles Bott2 • James Grandstaff3 • Steven Chiesa4 • Jared Alder5 • 1Hazen and Sawyer • 2HRSD • 3Henrico County DPU • 4Santa Clara University • 5OpenCEL

  2. Outline • Nansemond TP Overview • Co-Fermentation Pilot • Results and Discussion • Future Work • Henrico County WRF Overview • OpenCEL Pilot • Results and Discussion • Future Work • Conclusions and Lessons Learned

  3. Nansemond Treatment PlantSuffolk, VA • 30 mgd Design Flow • 5-StageBardenpho • Annual Average TN (5.0 mg/L) and P (1.0 mg/L) goals

  4. Low sCOD:TKN PCE, high industrial load Waste methanol: $1,800/d for denitrification EBPR preferred over chemical P precipitation due to an Ostarastruvite reactor on site Primary Solids are pumped at around 340,000 gpd (10 dT/day) Grease Trap Waste (GTW) haulers regularly discharge 5,600 gpd on average (0 to 15,000 gpd) Additional 2,000 – 9,000 gpd GTW could be diverted from other facilities Low electrical energy cost does not justify installation of CHP, co-digestion of GTW is not needed Local Conditions

  5. Study Overview • PS and GTW Fermentation: • Produce onsite carbon for denitrification • Offset supplemental carbon purchase • Remove GTW from NTP’s mainstream process • Enhance biological phosphorus removal • Pilot Objectives: • Determine VFA and rbCOD production from GTW and PS • Determine optimal ratio of GTW:PS (fermenter) and GTW:ADS (blend tank) • Evaluate effect of temperature and SRT on fermentation

  6. Pilot Overview

  7. Pilot Overview

  8. Primary Sludge Feed Characteristics tCOD:TKN = 45.7 sCOD:TKN= 1.66 tCOD:TP= 205.6 sCOD:TP = 7.44

  9. Grease Trap Waste Feed Characteristics tCOD:TKN = 225 sCOD:TKN = 18.1 tCOD:TP= 2,298 sCOD:TP = 185.2

  10. Primary Sludge Treatment Train • Impeller Mixed • 200 rpm • 30 cm (12”) impeller Elutriation • Gravity Thickener • 0.34 m3 (90 Gallon) • HRT: 9 hr • Underflow: 2% TS • Fermenter • Working Volume: 300 Gallon • HRT: 24 hr • TS: 1.4% • pH: 5.3-5.8 • ORP: -350 - -500 mV Recycle Pump Waste Pump

  11. Grease Trap Waste Treatment Train Blend Tank - 5 gallons Hydrolyzing lipids 40% GTW & 60% ADS (v:v) HRT: 7-10 hr Pump Mixed pH: 5.6 - 5.9 Headspace Gas: 13% Methane 70 % CO2 17% Bal Wet Tip Gas Meter

  12. Operating Criteria Fermenter Blend Tank

  13. Fermenter pH pCOD conversion to sCOD Effluent sCOD (lbs/day) Effluent VFA (lbs/day) Evaluation Criteria

  14. pCOD Conversion Summary 2.75 day 26-30 C 2 day 25-28 C 5 day 19-25 C 5 day 19-22 C 6.5 day 17-20 C

  15. Incremental GTW pCOD Conversion 15 minute blend tank SRT PS + ADS + GTW 9 hour blend tank SRT ADS + GTW

  16. Incremental GTW pCOD Conversion 13 hour blend tank SRT ADS + GTW

  17. sCOD and VFA Summary lbs/day lbs/day

  18. Expected Full Scale Fermenter Performance

  19. 6 to 14% of feed Primary Sludge pCOD can be converted to sCOD VFAs generally make up 50% to 70% of effluent sCOD A short HRT blend tank with 20:1 GTW:ADS allowed for an incremental degradation of up to 6% A longer HRT blend tank with 7:10 GTW:ADS ratio allowed up to 20% incremental degradation of grease trap waste Unknown whether grease degradation comes at the expense of some primary sludge degradation PS and GTW is expected to offset ~50% of facility supplemental carbon demand Conclusions

  20. Continue blend tank modifications to determine effect on LCFA degradation Possible staged fermentation Bench Scale SBRs to determine fermentate value as supplemental carbon source Denitrification Biological Phosphorus Removal Business Case Evaluation Next Steps

  21. Henrico County Water Reclamation Facility 75 mgd Facility Low TN and TP Limits

  22. Henrico County WRF Current Operations • GBT WAS thickening • Blended feed to digesters • BFP dewatering • Cake storage on site • Glycerol product used for denitrification carbon source Hydrogen Oxygen Carbon

  23. What is OpenCEL?

  24. OpenCel System Images: OpenCel

  25. OpenCel Theory • Focused electrical pulse treatment • Cyclic exposure to positive and negative charges weakens the cell wall • Eventually the cyclic forces cause cell rupture and release of internal contents

  26. OpenCel Impacts Images: OpenCel

  27. Pilot Testing Goals • Determine chemical and physical characteristics of TWAS before and after FP treatment. • Characterize the short-term impactof FP treated TWAS on denitrification activity. • Characterize the long-term impactof FP treated TWAS on denitrification activity. • Characterize the impact of FP treated TWAS addition on nutrient removal performance at HCWRF. Oxygen Nitrate Denitrification Carbon Nitrification Oxygen Nitrite NitrogenGas Ammonia

  28. Experimental Configuration

  29. OpenCel Container

  30. Focused pulse treatment releases soluble COD that can be used for denitrification • Sampled on two occasions in January and February 2013 ssCOD Yield ~ 7 to 9 % of TS

  31. Short term batch test data suggests that treated TWAS has a superior nitrate reduction rate • Note that non-treated TWAS also has higher nitrate reduction rate 31

  32. Full-scale COD characterization experiments were performed • Samples collected and filtered onsite immediately through 1.2 mm filters • Value were cross-checked with independent measurements Yield from initial full-scale experiments = 0.01 mg ssCOD/mg TS Predicted yield from bench-scale experiments = 0.09 mg ssCOD/mg TS OpenCel working to increase ssCOD yield from full-scale pilot

  33. Experimental Configuration Scenario 1 30% of glycerol dose • Currently Henrico adds glycerol to pre-anoxic and post-anoxic zones for denitrification • OpenCel treated TWAS will be fed to the pre-anoxic zone 4.87 mgd PE 70% of glycerol dose RAS

  34. Experimental Configuration Scenario 2 50% of glycerol dose 4.87 mgd PE 50% of glycerol dose RAS

  35. Implications for pilot testing • Assume yield is 0.09 mg ssCOD/mg TS • 20 gpmOpenCel flow • Assume yield is 0.01 mg ssCOD/mg TS • 20 gpmOpenCel flow

  36. Additional Considerations • FP treated TWAS will return significant TSS • MLSS will increase if wasting is not increased • Increased wasting will reduce cell residence time • May impact nitrification • TWAS recycle can act as bioaugmentation if cells are not inactivated

  37. Insights from Process Modeling • At 23 deg C and 15 gpmOpenCel and assuming no biomass inactivation in the OpenCel stream • Fourfold increase in WAS rate is needed to maintain reasonable mixed liquor concentration • Despite this increase in WAS rate and corresponding SRT reduction, nitrification is not significantly impacted • Bioaugmentation from OpenCel stream is crucial for helping to maintain complete nitrification • At 12 deg C and 15 gpmOpenCel and assuming no biomass inactivation in the OpenCel stream • Fourfold increase in WAS rate is still needed to maintain reasonable mixed liquor concentration • Nitrification is not significantly impacted • Bioaugmentation from OpenCel stream helps maintain nitrification at lower temperatures

  38. Insights from Process Modeling • At 23 deg C and 15 gpmOpenCel and assuming 100% biomass inactivation in the OpenCel stream • Fourfold increase in WAS rate is needed • Nitrification is not significantly impacted at 23 deg C • At 12 deg C and 15 gpmOpenCel and assuming 100% biomass inactivation in the OpenCel stream • Fourfold increase in WAS rate is needed • Nitrification performance is lost at the low temperature • It is expected that there will be between 0 and 100% inactivation through the OpenCel process, therefore: • Actual impact on nitrification will closely depend on the degree of inactivation as well as the mass of solids that will be recycled

  39. Next Steps • SBRs, at the HRSD lab, will be used to determine long term impacts of FP treated TWAS on denitrification activity • Impact of FP treated TWAS addition on nutrient removal performance at HCWRF will be tested in Spring 2014 • Business Case Evaluation

  40. Conclusions and Lessons Learned • Multiple sources of carbon within the wastewater treatment and collection system • High chemical costs and low energy costs can lead to GTW utilization or WAS pretreatment for supplemental carbon rather than biogas • GTW fermentation would still increase biogas production • ~60-85% of GTW COD is retained in wasted sludge • Evaluation must account for additional TSS, N, and P in “sustainable” supplemental carbon source

  41. Acknowledgments

  42. Hunter Long hlong@hazenandsawyer.com (919) 833-7152 ? Questions

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