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November 12, 2013

Take 2 – Biosolids Strategy Modifications for the City of Raleigh to Take Advantage of Technology Advancements. Tim Woody Resource Recovery Division Director, City of Raleigh Jonathan Treadway P.E, BCEE, CDM Smith. November 12, 2013. Presentation Outline. Project Background and Objectives

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November 12, 2013

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  1. Take 2 – Biosolids Strategy Modifications for the City of Raleigh to Take Advantage of Technology Advancements Tim Woody Resource Recovery Division Director, City of Raleigh Jonathan Treadway P.E, BCEE, CDM Smith November 12, 2013

  2. Presentation Outline • Project Background and Objectives • Biosolids Management Alternatives • Selected Project Direction • Implementation Plan • Conclusion TW

  3. City of Raleigh provides wastewater service to nearly 500,000 people • Neuse River WWTP • 44 mgd average • Smith Creek WWTP • 1.2 mgd • Little Creek WWTP • 0.7 mgd average TW

  4. Goals for Master Plan Update • Identify financially feasible management strategy • Demonstrate cost-effectiveness compared to the “base case” • Update 2008 Biosolids Master Plan with new technologies • Account for changing conditions • Advance the goals of the City’s EMS program for biosolids TW

  5. Changing Conditions Driving Update TW

  6. Changing Conditions Driving Update 2008 2012 TW

  7. Overview of Management Strategies Considered • * Base case includes diversified outlets: • Alkaline stabilized Class A product (Raleigh-Plus) • Third party composting • Aerobically digested Class B product • Landfill JT

  8. Management StrategiesAlt. 1 - Base Case (Aerobic Digestion) 57 DT/day 7 DT/day JT

  9. Management StrategiesAlt. 2 - Anaerobic Digestion + Solar Drying 40 DT/day • New Facilities Include: • New GBT Building • Three An. Digesters (2.75 MG each) • Biogas Storage • Upgraded Dewatering • 16 Solar Dryers JT

  10. Management StrategiesAlt. 3- Thermal Hydrolysis + Anaerobic Digestion + Solar Drying 32 DT/day • New Facilities Include: • Pre-screening and Pre-dewatering • Thermal Hydrolysis Equipment • Two An. Digesters (1.6 MG each) • Upgraded Dewatering • Biogas Storage • 8 Solar Dryers JT

  11. JT

  12. Comparison of Alternatives - 20 year net present worth JT

  13. Evaluation Criteria and Summary of Results Non-cost factors include: 1) regulatory requirements, 2) public health and environmental impacts, 3) outlet diversification, 4) operator friendliness, 5) ease of maintenance, plus 6 others.

  14. Recommended ImprovementsPre-Screening Platform • Free-standing outdoor structure • Two mechanical screens for co-settled sludge on top • Screening drop to dumpster below JT

  15. Recommended ImprovementsPre-Dewatering Facility • Pre-Dewatering (2-Story Bldg.) • Cake Bins Storage (Outdoors) TO THP CAKE BINS CENTRIFUGES THP FEED PUMPS • Screened solids are pre-dewatered by centrifuges • Discharged to outdoor cake bins using screw conveyors JT

  16. Recommended ImprovementsThermal Hydrolysis Process Flash Tank Pulper Reactors (3) Digester Feed Pumps

  17. Prestressed concrete tanks 64-ft diameter Cone bottom Draft tube mixers mounted to concrete cover Digester gas flare Adjacent digester building for pumps, etc. Outdoor heat exchangers for cooling sludge from THP Recommended ImprovementsAnaerobic Digesters

  18. Recommended ImprovementsFinal Dewatering Building • Option A: Reuse Existing Facilities • Refurbish or replace 3 BFPs • Continue to operate centrifuge • Ventilation and other improvements to mitigate corrosion problems • Can continue to use truck loading station • Option B: New Final Dewatering Building and Truck loading Station

  19. Recommended ImprovementsSolar Dryers • Eight modules, 42-ft x 435-ft • Fans, louvers, controls to optimize temperature and humidity for drying

  20. Recommended ImprovementsNutrient Recovery • Optional addition for enhanced sustainability • Reduce sidestream loading on liquid treatment process • Recover phosphorous • Third-party responsible for product marketing • Can be added at any time Photo Courtesy of Ostara JT

  21. Recommended ImprovementsCombined Heat and Power (CHP) Engine Generator • Single 1.75 MW generator • Containerized units available • Optional, but recommended for sustainability when THP is implemented • Generate electricity and heat • Requires biogas conditioning system • Engine can be purchased, leased, or procured via 3rd-party Energy Services Co. (ESCO) Photos Courtesy of GE JT

  22. Recommended ImprovementsImplementation Schedule TW

  23. Recommended Improvement Planvs. 2008 Master Plan TW

  24. Thank you

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