NEW YORK WATER ENVIRONMENT ASSOCIATION WINTER MEETING – FEBRUARY 10, 2003

1. NEW YORK WATER ENVIRONMENT ASSOCIATIONWINTER MEETING – FEBRUARY 10, 2003 MAXIMIZING CSO CAPTURE THROUGH WET WEATHER OPERATIONS AT WPCP’S

2. Background Of Topic And Authors • Topic • NYC DEP Is Currently Establishing Wet Weather Capacities and Protocols For All Of Its WPCP’s Which Service Combined Sewer Drainage Areas • NYS Has Established Wet Weather Operating Guidelines and Technology Transfer Materials www.dec.state.ny.us/website/dow/bwcp/foas_main.html • Authors • James Mueller, Stephane Gobbons and Dorothy Chao New York City Department of Environmental Protection Bureau of Environmental Engineering • Gary Grey HydroQual, Inc.

3. Why Maximize Treatment of Wet Weather Flows • Minimize Water Quality Impairments • Bathing Beach Closures (due to Coliform) • Floatables Impacts (due to street litter and sanitary materials) • CSO Sediments (due to settleable solids) • Avoid or Minimize Need For New CSO Treatment Facilities • Tanks, Screens, Nets, Skimmer Vessels • Regulatory Compliance • EPA Nine Minimum Controls • NYS DEC 13 CSO BMP’s • SPDES Permits

4. Federal and State CSO BMP’s • EPA Nine Minimum Controls #4 Maximizing Flow to POTW • Maximize sewer capacity through proper O&M • Analyze records to correlate flow and plant performance • Determine plant’s ability to accept incremental flow increases • NYSDEC BMP #4 Maximizing Flow to POTW • Particularly critical in treatment of “first flush” • Collection system and headworks must be capable of delivering flow up to treatment process capacity during wet weather • 2xDDWF+

5. SPDES Requirement for Maximizing Treatment of Wet Weather Flows “Factors cited in Item 2. above shall also be considered in maximizing flow to the POTW. Maximum delivery to the POTW is particularly critical in treatment of “first-flush”. The _______ treatment plant shall be physically capable of receiving the peak design hydraulic loading rates for all process units. The _______ treatment plant shall be physically capable of receiving a minimum of _____ MGD through the plant headworks; a minimum of _____ MGD through the primary treatment works (and disinfection works if applicable; and a minimum of _____ MGD through the secondary treatment works during wet weather. The actual process control set points may be established by the Wet Weather Operating Plan required in BMP #4. The sewer collection system, regulating devices and head works must be capable to delivering these flows during wet weather.

6. How To Maximize Treatment of Wet Weather Flows • Review Plant Performance for Significant Wet Weather Events • Identify Critical Treatment Processes • Establish Wet Weather Capacities and Wet Weather Operating Protocols • Anticipate Wet Weather Events

7. Characterizing Plant Impacts • Monitor influent characteristics and inter-process performance under wet weather conditions • Monitor critical process operations during wet weather • Develop a database to document plant response to wet weather flows • Utilize data to make process decisions for wet weather events

8. 400 350 Plant Peak Design Flow = 300 MGD 300 250 Flow (MGD) 200 150 Design Dry Weather Flow = 150 MGD 100 50 0 07/01/99 08/20/99 10/09/99 11/28/99 01/17/00 03/07/00 04/26/00 06/15/00 Daily Avg Dry Flow Hourly Peak Hourly Min Aeration Flow Bypass Flow Review Plant Flows

9. Review Performance for Significant Rain Events 400 350 300 250 Average Peak Flow (MGD) 200 150 100 50 0 1994 1995 1996 1997 1998 1999 2000

10. Review Plant Flow response to Wet Weather Conditions • NYC produces ~ 3 mgd of Dry Weather Flow per 1 mi 2 • 0.1” of rain over a 1mi 2 will produce >1.5 MG Actual Flow Average Dry Weather Flow

11. Is There Any Demonstrated Impact of Wet Weather Flow on WPCP Performance Plant Design 60 mgd

12. Are There Any SPDES Compliance Problems Associated With Wet Weather Flows Look at: BOD TSS Settleable Solids Fecal Coliform Cl2 Residual

13. Anticipate Wet Weather www.weather.com www.accuweather.com www.intellicast.com

14. Operating and Design Issues Which Can Influence Wet Weather Capacity • Ability to control flow accurately • Process capacity • Manual vs automatic controls • Process bypass capability • Flow meter accuracy • Human factors

15. Impacts At Wastewater Treatment Facilities - First Flush • High grit loading • High screenings loading • High BOD and suspended solids loading • Short term increase in residuals handling • Variable chlorine demand

16. Potential Impacts At Wastewater Treatment Facilities - Long Duration • Excess grit passing through grit removal facilities • Reduced primary clarifier efficiency • Reduced hydraulic detention time in secondary treatment process • Solids washout from secondary clarifiers • Reduced contact time in disinfection processes

17. Operations Guidelines - General • Assure that EVERYTHING is ready to go • Place unused equipment & tankage in service • Controlled bypassing • Minor modifications for flexibility • Reduce recycle flows • Watch weather

18. REVISED PUMP-ON LEVEL TO TAKE ADVANTAGE OF PIPE STORAGE PUMP-ON LEVEL PUMP-OFF LEVEL Operations Guidelines - Pump Stations • Modify pump control systems to: • Maximize wet well storage • Induce available collection system storage • Dampen flow surges to treatment processes • Bring stand-by pumps online

19. Operations Guidelines - Screening NYS Guidelines • Place all screening units in service • Increase screen cleaning frequency • Prepare screenings containers

20. Operations Guidelines - Grit Removal • Clean sewers, interceptors & catch basins regularly • Place all grit removal units in service • Shut off air to aerated grit chambers • Increase grit removal rate • Adjust velocity controlled grit chambers • Prepare grit containers

21. Operations Guidelines - Primary Settling • Place all units in service • Maintain low sludge blanket levels • Assure balanced flow • Consider chemical addition • Increase scum removal rate • Monitor primary sludge concentration • Discontinue secondary sludge wasting

22. Operations Guidelines - Activated Sludge • Control sludge quality (avoid filamentous sludge) • Adjust return sludge rate • Manage aeration • Change mode of operation • Conserve biomass

23. Lower or Shut Off Air In Last Passes of Aeration Tanks NYS Guidelines

24. Operations Guidelines Secondary Settling • Place all clarifiers in service • Maintain low sludge blanket levels • Balance flows to clarifiers • Consider chemical addition to aid settling

25. Operations Guidelines - Disinfection NYS Guidelines • Place all units in service • Manage chlorination rates • Chlorine demand will increase if bypassing primary effluent • Clean solids from contact tank regularly • Increase residual monitoring

26. Summary • Analyze plant performance during wet weather and establish reasonable goals • Establish operating procedures, follow them and and update them • Preserve the integrity of the plant • The benefits: • Preserve designated uses (fewer beach closings) • Compliance with CSO policies • Avoid the need for additional facilities

27. More WWOP Information www.dec.state.ny.us/website/dow/bwcp/foas_main.html Click on Wet Weather Training