Transcript Future Effluent Limits Study PAR 1054 Metro Wastewater Reclamation District

Future Effluent
Limits Study
PAR 1054
Metro Wastewater Reclamation District
March 20, 2007
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Agenda
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Project Background
TSD Background
How we used the TSD
Questions
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Project Background
• Prepare for Metro District’s permit renewal in 2008
• Evaluate proposed ammonia and nitrate limits
derived from WQ modeling
• Review treatment options used by other WWTPs to
meet similar effluent limits.
• Limits will drive the scope and timing of infrastructure
improvements and operations at the CTP
• Evaluate permitting alternatives that
– Protect Downstream Uses
– Provide Operations Flexibility
– Reasonable Monitoring and Compliance
Schedule
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Project Background
• Treatment Plant Summaries
– Upper Occoquan Sewage Authority (UOSA) –
Regional WRF, Centreville, Virginia
– Clean Water Services (CWS) – Rock Creek WRF,
Hillsboro Oregon
– District of Columbia Water and Sewer Authority
(DCWASA) – Blue Plains Advanced WWTP,
Washington D.C.
– Alexandria Sanitation Authority- Advanced
Wastewater Treatment Facility (AWTF),
Alexandria, Virginia
– Stamford Water Pollution Control Authority
(WPCA) – Stamford Wastewater Treatment Plant,
Stamford, Connecticut
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Project Background
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Treatment Plant Summaries
– Stamford Water Pollution Control Authority (WPCA) –
Stamford Wastewater Treatment Plant, Stamford,
Connecticut
– Inland Empire Utilities Agency (IEUA) - Carbon Canyon
Water Reclamation Facility (CCWRF), Chino, California
– Hampton Roads Sanitation District (HRSD) - Virginia
Initiative Plant (VIP), Norfolk, Virginia
– City of Calgary - Bonnybrook WWTP, Alberta, Canada
– City of Los Angeles -Los Angeles-Glendale Water
Reclamation Plant (LAGWRP), Glendale, California
– City of Grand Island - Grand Island Wastewater
Treatment Facility (GIWWTF), Grand Island, Nebraska
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Project Background
• Modeling Alternatives:
– Reduced CBOD discharge limit
– Reduced Discharge Flows
• No single strategy worth pursuing
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Project Background
• Non-Modeling Alternatives:
– Application of human health-based nitrate water
quality standards in other states
– Federal permitting language that is supportive of
a 7-day averaging period for nitrate
– Basis for the drinking water standard for nitrate
– Well withdrawal of drinking water supplies
– Cost comparison for nitrate treatment between
water treatment plants and wastewater treatment
plants
– Statistical basis for longer effluent nitrate
concentration compliance periods (TSD)
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TSD Background
• TSD: EPA’s Technical Support Document for
Water Quality-based Toxics Control
• Technical guidance for assessing and
regulating the discharge of toxic substances
to surface water
• Includes detailed discussion on effluent
variability
• Provides recommendations for deriving
permit limits from wasteload allocations
– human health based WQ standards or
– water quality modeling
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TSD Background
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TSD Background
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TSD Background
• Coefficient of Variation:
Standard Deviation
Mean
• TSD allows the use of calculated CVs
• TSD allows the use of “default” CV=0.60
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TSD Background
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TSD Background
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How we used the TSD
• Used Metro Past Effluent data to calculate
the Coefficient of Variation
– Lower variation for nitrate than CV=0.60
– Slightly higher variation for Ammonia
than CV=0.60
• Converted the Human-Health Based Acute
Nitrate Wasteload Allocation of 10 mg/L into
a (lower) permit limit over longer averaging
period
– Used 95% prob. for 7-day average (8.68)
– Used 99% prob. for 30-day ave. (8.14)
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How we used the TSD
• Converted the WQ Model Acute Ammonia
Wasteload Allocation (varies by month) into
a (lower) permit limit over longer averaging
period
– Used 95% probability for 7-day average
(Varies monthly minimum is 1.75 in Aug)
– Used 99% probability for 30-day average
(Varies monthly minimum is 1.46 in Aug)
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Questions
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