201 529 5151 new york water environment association winter meeting – february 10, 2003 maximizing...
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201• 529 • 5151www.hydroqual.com
NEW YORK WATER ENVIRONMENT ASSOCIATIONWINTER MEETING – FEBRUARY 10, 2003
NEW YORK WATER ENVIRONMENT ASSOCIATIONWINTER MEETING – FEBRUARY 10, 2003
MAXIMIZING CSO CAPTURE THROUGH WET WEATHER OPERATIONS AT WPCP’S
Background Of Topic And AuthorsBackground 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 GreyHydroQual, Inc.
Why Maximize Treatment of Wet Weather Flows
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
Federal and State CSO BMP’sFederal 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+
SPDES Requirement for Maximizing Treatment of Wet Weather Flows
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.
How To Maximize Treatment of Wet Weather Flows
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
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
Review Plant FlowsReview Plant Flows
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07/01/99 08/20/99 10/09/99 11/28/99 01/17/00 03/07/00 04/26/00 06/15/00
Flo
w (
MG
D)
Daily Avg Dry Flow Hourly Peak Hourly Min Aeration Flow Bypass Flow
Design Dry Weather Flow = 150 MGD
Plant Peak Design Flow = 300 MGD
Review Performance for Significant Rain EventsReview Performance for Significant Rain Events
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1994 1995 1996 1997 1998 1999 2000
Ave
rag
e P
eak
Flo
w (
MG
D)
Review Plant Flow response to Wet Weather Conditions
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
Average Dry Weather Flow
Actual Flow
Is There Any Demonstrated Impact of Wet Weather Flow on WPCP Performance
Is There Any Demonstrated Impact of Wet Weather Flow on WPCP Performance
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Peak Hourly Flow (mgd)
Pla
nt
Eff
lue
nt
TS
S (
mg
/L)
Current 7-Day Arithmetic Average Limit 45 mg/L
Current 30-Day Arithmetic Average Limit 30 mg/L
Future Daily Maximum Limit 50 mg/L(does not apply when wet weather flows exceed 2xDDWF)
Plant Design 60 mgd
Are There Any SPDES Compliance Problems Associated With Wet Weather Flows
Are There Any SPDES Compliance Problems Associated With Wet Weather Flows
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7/4/
1999
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/199
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8/1/
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8/29
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10/2
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11/7
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12/5
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12/1
9/19
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1/2/
2000
1/16
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1/30
/200
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2/13
/200
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2/27
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3/12
/200
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4/23
/200
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SS
(m
g/L
)
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5,000
7,500
10,000
12,500
15,000
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20,000
22,500
25,000
SS
(lb
/da
y)
Conc Load_DWF Load_TotalFlow
Permit Limit = 45 mg/L, 22,518 lb/d
Look at:BODTSS Settleable SolidsFecal ColiformCl2 Residual
Anticipate Wet WeatherAnticipate Wet Weather
www.weather.com
www.accuweather.com
www.intellicast.com
Operating and Design Issues Which Can Influence Wet Weather Capacity
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
Impacts At Wastewater Treatment Facilities - First Flush
High grit loadingHigh screenings loadingHigh BOD and suspended solids loadingShort term increase in residuals handlingVariable chlorine demand
Potential Impacts At Wastewater Treatment Facilities - Long Duration
Excess grit passing through grit removal facilitiesReduced primary clarifier efficiencyReduced hydraulic detention time in secondary
treatment processSolids washout from secondary clarifiersReduced contact time in disinfection processes
Operations Guidelines - General
Assure that EVERYTHING is ready to goPlace unused equipment & tankage in
serviceControlled bypassingMinor modifications for flexibilityReduce recycle flowsWatch weather
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
REVISEDPUMP-ON LEVEL
TO TAKEADVANTAGE OFPIPE STORAGE
PUMP-ONLEVEL
PUMP-OFFLEVEL
Operations Guidelines - Screening
Place all screening units in service
Increase screen cleaning frequency
Prepare screenings containers
NYS Guidelines
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
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
Operations Guidelines - Activated Sludge
Control sludge quality (avoid filamentous sludge)
Adjust return sludge rate Manage aeration Change mode of operation Conserve biomass
Lower or Shut Off Air In Last Passes of Aeration Tanks
Lower or Shut Off Air In Last Passes of Aeration Tanks
NYS Guidelines
Operations Guidelines Secondary Settling
Place all clarifiers in service Maintain low sludge blanket
levels Balance flows to clarifiers Consider chemical addition
to aid settling
Operations Guidelines - Disinfection
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
NYS Guidelines
SummarySummary
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
More WWOP InformationMore WWOP Information
www.dec.state.ny.us/website/dow/bwcp/foas_main.html
Click on Wet Weather Training