future effluent limits study par 1054 metro wastewater reclamation district march 20, 2007
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Future Effluent Limits Study PAR 1054 Metro Wastewater Reclamation District March 20, 2007. Agenda. Project Background TSD Background How we used the TSD Questions. Project Background. Prepare for Metro District’s permit renewal in 2008 - PowerPoint PPT PresentationTRANSCRIPT
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Future EffluentLimits StudyPAR 1054Metro Wastewater Reclamation District
March 20, 2007
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Agenda
• 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
• 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:
• TSD allows the use of calculated CVs• TSD allows the use of “default” CV=0.60
Standard Deviation
Mean
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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