Toxicity Requirements for Water Treatment Plants Carol Hollenkamp NCDENR/DWQ Environmental Sciences Section Aquatic Toxicology Unit
Aquatic Toxicology Unit (ATU) Compliance & Enforcement Biological Laboratory Certification DWQ Toxicity Testing Laboratory http://portal.ncdenr.org/web/wq/ess/atu/wet
Which Permits Get Toxicity Testing? All major dischargers...major meaning Permitted Flow 1 MGD All facilities with a complex effluent...complex meaning anything other than 100% domestic waste Any facility for which available effluent monitoring data predicts a possible receiving stream impact
Instream Waste Concentration (IWC) IWC used in determining: Permit Limit Test Type Test Organism Organism also determined by salinity of receiving water IWC = Permitted Discharge x100 (Permitted Discharge + 7Q10)
Water Treatment Plant (WTP) Effluent Requirements Based on Assessment & Recommendations for WTP Permitting: Findings of the WTP Workgroup WTP Strategy requirements based on treatment Membrane Conventional Ion Exchange Greensand
Membrane & Ion Exchange (IE) 2002 Interagency workgroup formed due to toxicity concerns with Membrane/IE discharge 2004 Start Membrane/IE Permitting Strategy with quarterly toxicity monitoring 2013 Approximately 25-55% have high failure rates Many states issue Membrane/IE as Individual Permits due to greater environmental concerns
Conventional WTPs 2003 Study of 5 Conventional WTPs showed some toxicity failures 2007 Start Conventional WTP Permitting Strategy with quarterly Neuse Basin renewals 2012 Complete NPDES implementation of Conventional WTP Permitting Strategy by end of year 2013 Approximately 25% have high failure rate Fewer toxicity failures relative to Membrane/IE More solutions for conventional WTPs
Greensand WTPs 2007-Greensand Permitting Strategy: does NOT include toxicity testing Consideration for coverage under General Permit in future
Conventional WTP 2013: 66 reporting, ~20-25% failing 14 Failing All discharge to freshwater All test Chronic Ceriodaphnia @ 90% 48 Passing 7 test Acute Fathead @ 90% 41 test Chronic Ceriodaphnia @90% or IWC 1 discharge to Tidal Water Not all 66 facilities have enough test results to assess failure rates
Membrane: Reverse Osmosis & Nanofiltration 2013: 19 reporting, ~25% failing 5 Failing 4 discharge to saltwater (all are acute mysid tests at 90%) 1 discharge to freshwater 14 Passing 13 discharge to saltwater (6 are chronic mysid tests at IWC) 1 discharge to freshwater
Ion Exchange (IE) 2013: 33 reporting, ~50-55% failing 18 Failing 8 discharge to saltwater 10 discharge to freshwater 15 Passing 11 discharge to saltwater 4 discharge to freshwater
What have we learned? Think outside of the box! Cannot be solved in the same way as WWTPs Some have highly variable discharge composition and frequency Discharge frequency dependent on drinking water demand Source water variations Operation different from plant to plant
What have we learned? Saltwater Failures Acute pass/fail tests with mysid shrimp at 90% test concentration may be ion imbalance. Freshwater Failures Ion exchange: Likely due to high chlorides, although metals may also be a factor Conventional: Variable reasons, more easily solved than ion imbalance or high chloride
Future plans Monitoring only will continue through next permit cycle To address high rates of toxicity failures Toxicity Evaluation & Assessment Plan as part of permit renewal DWQ will provide guidance Evaluate possible solutions and cost-feasibility analysis
Solving Problems? Are representative samples being collected? Verify WET testing is being performed using appropriate test, organism, and proper instream waste concentration (IWC) Have multiple concentration tests been run? At what concentration will a facility pass a test?
7-day Chronic Test Schedule What if a WTP only discharges once a week? Sun Mon Tues Wed Thurs Fri Sat Sample 1 collected & shipped Test Initiated Sample 2 collected & shipped Test Renewed Exposure to Sample 1 Exposure to Sample 2 Test Renewed Test Ended Exposure to Sample 2 36-hour holding time for initial use of all samples (acute and chronic)
Solving problems Can operational changes be made? Blend wells differently, blend softened water with well water for distribution (less backwash), etc. Can wastewater treatment be added or improved? Can discharge be moved? Can a diffuser be added? IWC obtained?
Future NPDES WTP Goal for Conventional WTPs Facilities Passing WET tests Facilites showing no reasonable potential to violate water quality standards (i.e. metals) Facilities in compliance with all NC regulations and standards including inspections and monitoring NPDES Goal: issuance of a Water Treatment Plant General Permit (Conventional & Greensand)
Questions? 919-743-8401 http://portal.ncdenr.org/web/wq/ess/atu DWQ ATU Compliance/Reporting Contacts Cindy Moore Supervisor John Giorgino Compliance/Enforcement Susan Meadows Compliance/Reporting Lance Ferrell Laboratory Certification Carol Hollenkamp Toxicity Lab Christopher Ventaloro Toxicity Lab