1. Why Class A does not always make cents: Cost model to drive biosolids planning decisions Thor A. Young | Service Line Leader Sebastian E. Smoot | Engineer

2. GHD @ NC AWWA-WEA 2015 Acknowledgements Charles County Department of Public Works Bill Shreve Greg Boykin Ed Gorham Rea Schafer Olin Straus Sam Walter Sam Simanovsky GHD Kristi Perri Brandon Gott

3. Context & objectives

4. GHD @ NC AWWA-WEA 2015 Context Many municipal utilities considering upgrading their Class B biosolids operations to Class A Common project drivers: Less restrictions than Class B More outlets for distribution “Hedging their bets” against future Class B restrictions Biosolids volume reduction Increased biogas production “Greener” process/product Greater public acceptance Source: Scanlan et al. (2010). “Class A Digestion – What is its future in the US?” Proceedings of the Water Environment Federation. WEFTEC 2010.

5. GHD @ NC AWWA-WEA 2015 Typical operating costs for wastewater treatment Source: U. Halbach (2003) Abwasserentsorgung in Brandenburg, Orientierungswerte Jahr 2003, Land Brandenburg, 2003. http://cgi.tu-harburg.de/~awwweb/wbt/emwater/documents/lesson_c2.pdf

6. GHD @ NC AWWA-WEA 2015 Image placeholder Stock image of scale balance with coins? Cost considerations In evaluation of future biosolids management options, utilities must consider the following for Class A alternatives vs. current operations: Capital expenses (CAPEX) Operation and maintenance expenses (OPEX) Payback period Impact on rate payers Availability of funds for capital projects

7. Project background

8. GHD @ NC AWWA-WEA 2015 Mattawoman WWTP Located in Charles County, Maryland Design capacity: 20 MGD Current flow: 11 MGD (55%) Upgraded for ENR in 2003 Receives sludge from satellite facilities at the headworks A portion of plant effluent (5%) is reused Image Source: Bing Maps

9. GHD @ NC AWWA-WEA 2015 25-yr projections of flows and solids production

10. GHD @ NC AWWA-WEA 2015 Image placeholder Primary Clarifiers Secondary Clarifiers Admin. Bldg NORTH Final Clarifiers Aerobic Digesters Dewatering Building Gravity Thickeners Septage Receiving Reactors Image Source: Bing Maps Filters

11. GHD @ NC AWWA-WEA 2015 LEGEND Solids Scum Operated by Contractor Simplified solids process flow schematic Gravity Thickeners Aerobic Digesters 3 & 4 Aerobic Digesters 6 - 11 Septage Receiving Lime Stabilization Belt Filter Presses Land Application Thickening Stabilization Dewatering Primary Clarifiers Secondary Clarifiers Final Clarifiers Aerobic Digesters 1 & 5

12. GHD @ NC AWWA-WEA 2015 LEGEND Solids Scum Simplified solids process flow schematic Gravity Thickeners Aerobic Digesters 3 & 4 Aerobic Digesters 6 - 11 Septage Receiving Thickening Stabilization Dewatering Primary Clarifiers Secondary Clarifiers Final Clarifiers Aerobic Digesters 1 & 5 Operated by Contractor Mechanical Thickeners Land Application Thickened Combined Sludge to Stabilization and/or Dewatering (Multiple Alternatives) and other beneficial reuse

13. GHD @ NC AWWA-WEA 2015 Projection of solids flows at 20 MGD 19.3 Tons per day 29 Tons per day

14. GHD @ NC AWWA-WEA 2015 Existing Class B biosolids facility

15. Approach

16. GHD @ NC AWWA-WEA 2015 Technologies considered Thermal HydrolysisThermal DryerAnaerobic Digestion Thermal DryingThermal Hydrolysis

17. GHD @ NC AWWA-WEA 2015 Alternative 0 – status quo Class B lime stabilization Thickened Primary Sludge Thickened Secondary Sludge Class B Biosolids Dewatering (new centrifuges) Lime Stabilization

18. GHD @ NC AWWA-WEA 2015 Alternative 1 – TPAD Temperature-Phased Anaerobic Digestion Thickened Primary Sludge Thickened Secondary Sludge Class A Biosolids DewateringMesophilic Anaerobic Digestion (MAD) Thermophilic Anaerobic Digestion Cogeneration Electricity Natural Gas

19. GHD @ NC AWWA-WEA 2015 Alternative 2 – dryer Thermal dryer Thickened Primary Sludge Thickened Secondary Sludge Class A Biosolids Dewatering Drum Dryer Hopper

20. GHD @ NC AWWA-WEA 2015 Alternative 3 – AD + dryer Mesophilic anaerobic digestion followed by thermal dryer Thickened Primary Sludge Thickened Secondary Sludge Class A Biosolids Dewatering Drum Dryer Boiler MAD Hopper Natural Gas

21. GHD @ NC AWWA-WEA 2015 Alternative 4 – THP Thermal Hydrolysis Process and anaerobic digestion Thickened Primary Sludge Thickened Secondary Sludge Class A Biosolids MADDewatering Thermal Hydrolysis Process (THP) Cogeneration Hopper Electricity Natural Gas

22. GHD @ NC AWWA-WEA 2015 Alternative 5 – THP + dryer THP and anaerobic digestion followed by thermal dryer Thickened Primary Sludge Thickened Secondary Sludge Class A Biosolids MADDewatering Thermal Hydrolysis Process Paddle Dryer Boiler Hopper Natural Gas

23. GHD @ NC AWWA-WEA 2015 Summary of alternatives LEGEND Thermophilic Digester Mesophilic Digester Thermal Dryer Thermal Hydrolysis DW Dewatering DW Lime Cogeneration DW Cogeneration Heat Recovery Alt. 0 – Status Quo (Class B Lime Stabilization) Alt. 1 – Temperature-Phased Anaerobic Digestion (TPAD) Alt. 2 – Thermal Drying Alt. 3 – Mesophilic Anaerobic Digestion and Thermal Drying Alt. 4 – Thermal Hydrolysis and Anaerobic Digestion Alt. 5 – Thermal Hydrolysis, Digestion, and Thermal Drying

24. Approach

25. GHD @ NC AWWA-WEA 2015 Assumptions Land Application Unit Cost:Class A (90% solids):$25 per wet ton Class A (20-30% solids):$50 per wet ton Class B (20-30% solids):$75 per wet ton Contract Operations Unit Cost$100 per hour Regional Biosolids Revenue$70 per wet ton General Inflation Rate3% Land Application Cost Inflation Rate6% Nominal Discount Rate1.8% Cost of Electricity$0.13 per kWh Cost of Natural Gas$8 per MMBTU Cost of Polymer$2 per pound Cost of Lime$180 per ton Annual Maintenance Cost 3% of equipment cost

26. GHD @ NC AWWA-WEA 2015 Capital cost comparison

27. GHD @ NC AWWA-WEA 2015 O&M cost comparison

28. GHD @ NC AWWA-WEA 2015 Lifecycle cost comparison

29. GHD @ NC AWWA-WEA 2015 Lifecycle cost comparison

30. Results

31. GHD @ NC AWWA-WEA 2015 Lifecycle cost comparison over time AD+Dryer Class B THP+Dryer Dryer TPAD THP

32. Sensitivity Analysis

33. GHD @ NC AWWA-WEA 2015 Impact of increased cost of Class B land application Baseline Class A (90% solids) $25 per wet ton Class A (20-30% solids) $50 per wet ton Class B (20-30% solids) $75 per wet ton Adjusted inputs Class A (90% solids) $25 per wet ton Class A (20-30% solids) $50 per wet ton Class B (20-30% solids) $85/95 per wet ton

34. GHD @ NC AWWA-WEA 2015 Lifecycle costs at various Class B unit costs AD+Dryer Class B THP+Dryer Dryer TPAD THP $75/WT $85/WT $95/WT

35. GHD @ NC AWWA-WEA 2015 Impact of reduced costs of Class A land application Land application fees Baseline values Class A 90% solids $25 per wet ton Class A 20-30% solids $50 per wet ton Class B 20-30% solids $75 per wet ton Adjusted inputs Class A 90% solids $0 per wet ton Class A 20-30% solids $25 per wet ton Class B 20-30% solids $85/95 per wet ton

36. GHD @ NC AWWA-WEA 2015 Lifecycle costs at reduced Class A unit costs AD+Dryer Class B THP+Dryer Dryer TPAD THP $75/WT $85/WT $95/WT

37. GHD @ NC AWWA-WEA 2015 O&M cost comparison (reduced Class A unit costs) Baseline O&M Cost

38. GHD @ NC AWWA-WEA 2015 Lifecycle cost comparison (reduced Class A unit costs) Baseline Lifecycle Cost

39. Conclusions

40. GHD @ NC AWWA-WEA 2015 Image placeholder Conclusions Charles County opted to maintain Class B system for foreseeable future until new regulations or technologies result in cost advantages for Class A The impact of sudden and severe restrictions on Class B land application is a manageable risk for Charles County Clarifications –Study limited to financial analysis –GHG or carbon footprint not monetized –Did not examine grants or other funding sources

41. GHD @ NC AWWA-WEA 2015 Thank you! Questions? sebastian.smoot@ghd.com