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Rob Stephenson and Charles Liao Paradigm Environmental Technologies Inc.

Mitigating Greenhouse Gases From Biological Wastewater Treatment Plants. Rob Stephenson and Charles Liao Paradigm Environmental Technologies Inc. Outline . Energy and GHGs at a WWTP Biogas energy potential in sludge WWTP as a bioenergy centre

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Rob Stephenson and Charles Liao Paradigm Environmental Technologies Inc.

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  1. Mitigating Greenhouse Gases From Biological Wastewater Treatment Plants Rob Stephenson and Charles Liao Paradigm Environmental Technologies Inc.

  2. Outline Energy and GHGs at a WWTP Biogas energy potential in sludge WWTP as a bioenergy centre Sludge pre-treatment and advanced co-generation Example: Lulu Island WWTP Conclusions

  3. How WWTPs generate GHGs • By consuming electricity and natural gas • By generating CO2 from biological wastewater treatment • By generating excess microorganisms that: • Require trucking and disposal • Rot, forming CH4, CO2, N2O

  4. Activated sludge wastewater treatment Electricity is used for blowers to aerate wastewater For organic load of incoming sewage: ~ 50% is converted to CO2 ~ 50% is converted to bacteria

  5. Anaerobic digestion of sludge Anaerobic Digesters >15 days pumping, mixing, heating at 37ºC Stabilize primary sludge, waste activated sludge Generate biogas (60-65% CH4, 35-40% CO2) Poor Efficiency ~30% destruction of WAS ~60% destruction of primary sludge

  6. Energy recovery systems Typical Co-generation Efficiency 30% conversion of biogas to electricity 50% recovery of waste heat

  7. Heat generation at a WWTP Typical Boiler Efficiency 80 - 90% to useable heat

  8. GHG impacts for land application of sludge Aerobic Degradation: C5H7O2N + 5O2 -> 2H2O + NH3 + 5CO2 (sludge) Anaerobic Degradation: 2C5H7O2N + 6H2O -> 5CH4 + 2NH3 + 5CO2

  9. GHG impacts for landfilling sludge Anaerobic Degradation: 2C5H7O2N + 6H2O -> 5CH4 + 2NH3 + 5CO2 Aerobic Degradation: C5H7O2N + 5O2 -> 2H2O + NH3 + 5CO2

  10. GHG impacts for sludge incineration Sludge Combustion: C5H7O2N + 6.25O2 -> 3.5H2O + NO + 5CO2 Fuel Combustion: CH4 + 2O2 -> CO2 + 2H2O

  11. Biogas energy potential of sludge

  12. Biogas energy potential of sludge for a WWTP serving 1 million people • 30% conventional, 42% ARES • 40 – 50% recovery of waste heat (3) 5¢/kWh electricity, 3¢/kWh natural gas

  13. Bioenergy infrastructure requirements

  14. Why WWTPs are net energy consumers • Energy Uses • Aeration for secondary wastewater treatment • Heating, pumping, mixing anaerobic digesters • Sludge conveying and dewatering • Hauling and disposal of residual sludge • Potential for Energy Recovery • Anaerobic digestion • Co-generation

  15. Why does WAS digest so poorly? Extremely tough cell membranes retard degradation in anaerobic digesters Conventionally, VSr of WAS ≤ 30% • limits biogas production MicroSludge increases VSr of WAS to up to 90% • maximizes biogas production

  16. WAS pre-treatment options • Heat • Freezing • Chemicals • Enzymes • Shear • Pressure

  17. MicroSludge process

  18. Sheer Forces Lyse Cells WAS liquefied WAS liquefied 12,000 psi 700 mph Cell disrupter valve LYSED CELLS IMPACT RING TWAS (INTACT CELLS) VALVE STEM VALVE SEAT LYSED CELLS

  19. How MicroSludge can make anaerobic digesters work better After MicroSludge Before MicroSludge

  20. Advanced Reciprocating Engine System • ARES: High efficiency, low emissions gas engine • US DOE, Caterpillar, Cummins, Waukesha Engine • Biogas to electricity efficiency: 42% now, target 50% • (Conventional efficiency 30%) • Reduces NOX by 90%

  21. Synergy of MicroSludge + ARES + * Estimate from GVRD

  22. Biogas energy potential of sludge

  23. Example of Lulu Island WWTP Lulu Island WWTP services 170,000 people and businesses in Richmond, BC treating 80,000 m3/day of wastewater

  24. Lulu Island WWTP: current operations

  25. Lulu Island WWTP + MicroSludge + ARES

  26. Benefits of MicroSludge + ARES at Lulu

  27. GHGs and sludge disposal options

  28. How WWTPs can minimize GHG generation • Maximize conversion of sludge to biogas • Maximize co-generation efficiency • Displace non-renewable energy with biogas energy • Minimize quantity of sludge hauled off site: • Landfill • Land application • Incineration

  29. Conclusions • Cities are flush with bioenergy potential • Guaranteed supply • Guaranteed buyer • Infrastructure already exists • New innovations of (1) MicroSludge • + (2) ARES co-generation: • Transform municipal WWTPs from • energy blackholes into • renewable energy showpieces

  30. Ode to sludge • Sludge, oh sludge - • Vile yucky muck! • By treating wastewater, • We haul it from cities by truck. • But farmers don’t want it. • And it’s too wet to burn. • So anaerobically digest it. • And do Mother Nature a good turn.

  31. Questions?

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