Transcript Wet Weather Treatment Capacity

NEW YORK WATER ENVIRONMENT ASSOCIATION
WINTER MEETING – FEBRUARY 10, 2003
MAXIMIZING CSO CAPTURE THROUGH
WET WEATHER OPERATIONS AT WPCP’S
201• 529 • 5151
www.hydroqual.com
Background Of Topic And Authors
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Topic
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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
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Authors
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James Mueller, Stephane Gobbons and Dorothy Chao
New York City Department of Environmental Protection
Bureau of Environmental Engineering
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Gary Grey
HydroQual, Inc.
Why Maximize Treatment of
Wet Weather Flows
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Minimize Water Quality Impairments
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Avoid or Minimize Need For New CSO
Treatment Facilities
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Bathing Beach Closures (due to Coliform)
Floatables Impacts (due to street litter and
sanitary materials)
CSO Sediments (due to settleable solids)
Tanks, Screens, Nets, Skimmer Vessels
Regulatory Compliance
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EPA Nine Minimum Controls
NYS DEC 13 CSO BMP’s
SPDES Permits
Federal and State CSO BMP’s
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EPA Nine Minimum Controls
#4 Maximizing Flow to POTW
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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
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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
“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
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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
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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 Flows
400
350
Plant Peak Design Flow = 300 MGD
300
Flow (MGD)
250
200
150
Design Dry Weather Flow = 150 MGD
100
50
0
07/01/99
08/20/99
Daily Avg
10/09/99
Dry Flow
11/28/99
Hourly Peak
01/17/00
Hourly Min
03/07/00
Aeration Flow
04/26/00
06/15/00
Bypass Flow
Review Performance for Significant Rain Events
Average Peak Flow (MGD)
400
350
300
250
200
150
100
50
0
1994
1995
1996
1997
1998
1999
2000
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
Is There Any Demonstrated Impact of Wet
Weather Flow on WPCP Performance
100
90
Plant Effluent TSS (mg/L)
80
70
60
Future Daily Maximum Limit 50 mg/L
(does not apply when wet weather flows exceed 2xDDWF)
50
Current 7-Day Arithmetic Average Limit
45 mg/L
40
Current 30-Day Arithmetic Average
Limit 30 mg/L
30
20
10
0
0
20
40
Plant Design 60 mgd
60
80
100
120
Peak Hourly Flow (mgd)
140
160
180
200
Are There Any SPDES Compliance Problems
Associated With Wet Weather Flows
50
25,000
45
22,500
Permit Limit = 45 mg/L, 22,518 lb/d
40
20,000
Look at:
BOD
TSS
Settleable Solids
Fecal Coliform
Cl2 Residual
25
20
17,500
15,000
12,500
10,000
Conc
Load_DWF
Load_TotalFlow
6/18/2000
6/4/2000
5/21/2000
5/7/2000
4/23/2000
4/9/2000
3/26/2000
3/12/2000
2/27/2000
2/13/2000
1/30/2000
1/16/2000
1/2/2000
12/19/1999
12/5/1999
11/21/1999
11/7/1999
10/24/1999
0
10/10/1999
0
9/26/1999
2,500
9/12/1999
5
8/29/1999
5,000
8/15/1999
10
8/1/1999
7,500
7/18/1999
15
SS (lb/day)
30
7/4/1999
SS (mg/L)
35
Anticipate Wet Weather
www.weather.com
www.accuweather.com
www.intellicast.com
Operating and Design Issues Which Can
Influence Wet Weather Capacity
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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
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High grit loading
High screenings loading
High BOD and suspended solids loading
Short term increase in residuals handling
Variable chlorine demand
Potential Impacts At Wastewater
Treatment Facilities - Long Duration
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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
Operations Guidelines - General
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Assure that EVERYTHING is ready to go
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Place unused equipment & tankage in
service
Controlled bypassing
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Minor modifications for flexibility
Reduce recycle flows
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Watch weather
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Operations Guidelines - Pump Stations
REVISED
PUMP-ON LEVEL
TO TAKE
ADVANTAGE OF
PIPE STORAGE
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PUMP-ON
LEVEL
PUMP-OFF
LEVEL
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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
Operations Guidelines - Screening
NYS Guidelines
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Place all screening units in service
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Increase screen cleaning frequency
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Prepare screenings containers
Operations Guidelines - Grit Removal
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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
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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
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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
NYS Guidelines
Operations Guidelines
Secondary Settling
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Place all clarifiers in service
Maintain low sludge blanket
levels
Balance flows to clarifiers
Consider chemical addition
to aid settling
Operations Guidelines - Disinfection
NYS Guidelines
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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
Summary
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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:
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Preserve designated uses (fewer beach closings)
Compliance with CSO policies
Avoid the need for additional facilities
More WWOP Information
www.dec.state.ny.us/website/dow/bwcp/foas_main.html
Click on Wet Weather Training