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Copper Removal at the Vail Wastewater Treatment Plant

2002 RMSAWWA / RMWEA Joint Annual Conference. Copper Removal at the Vail Wastewater Treatment Plant. Eagle River Water and Sanitation District HDR, Inc. Copper Removal??. Receiving Stream Gore Creek Gold Medal Trout Stream Discharge Limit 27 ug/L monthly average 35 ug/L daily maximum

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Copper Removal at the Vail Wastewater Treatment Plant

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  1. 2002 RMSAWWA / RMWEAJoint Annual Conference Copper Removal at the Vail Wastewater Treatment Plant Eagle River Water and Sanitation DistrictHDR, Inc.

  2. Copper Removal?? • Receiving Stream • Gore Creek • Gold Medal Trout Stream • Discharge Limit • 27 ug/L monthly average • 35 ug/L daily maximum • Limit is 44 Times Lower than Drinking Water Action Level

  3. Influent Copper Levels

  4. Vail WWTP • Plant Rating: 2.7 MGD • Process Train: • Screening • Grit removal • Aeration basins • Secondary clarification • Nitrification • Upflow fixed film configuration • Disinfection • No solids handling – sent to Avon WWTP

  5. The discharge is largely dissolved Cu – not particulate. WWTP Cu Levels 30  Test 1 Test 2 Test 3 Cu Concentration (µg/L) 20  10  Dissolved Particulate The particulate fraction could easily be removed via filtration. The dissolved fraction must be chemically treated.

  6. Dissolved Cu levels cannot be achieved via solubility control. 10-4  10-5  [Cu] solubility 10-6  Discharge Limit 10-7  5 6 7 8 9 10 pH The dissolved Cu must be absorbed / co-precipitated.

  7. Enhanced Cu Removal Options • Option 1: Microsand-Assisted Oxidation Adsorption (MAOA) • Option 2: Green Sand Filtration • Option 3: Manganese Oxide Co-Precipitation

  8. 4MnO2 + MnO(OH) + K2SO4 3KMnO4 + 2MnSO4 Process • Manganic-oxide precipitates have strong affinity for dissolved Cu • Manganic-oxide precipitates form quickly • Manganic-oxide precipitates are “sticky”

  9. Microsand-Assisted Oxidation Adsorption (MAOA) • 100 mesh fine sand is fluidized in a long column by feed water introduced in an upflow mode. • Manganese (manganese sulfate) and oxidant (permanganate) are added to the water at the base of the column, resulting in MnO2 coated sand. • Fresh manganic oxide surfaces sorb copper from the water. • Developed by Krüger (MetCleanTM), Denmark

  10. MAOA Pilot Unit 20 foot tall column

  11. MAOA Fluidized Sand Fluidized sand seen from the glass viewing section. Reddish brown color is from iron oxide coating of the sand.

  12. Advantages of the MAOA Process: • Process does not produce sludge. • The residual product from the MetCleanTM process is less than 10% of the sludge production from a normal precipitation process. • Granular / residuals product does not need secondary treatment. • The concentration of heavy metals on the granular surfaces is normally between 0.5 and 8%. • The granular surface normally consists of 2/3 of the total weight of the waste product.

  13. WasteBackwashTank Copper Removal with Permanganate Oxidation and Greensand Filtration Multi-CellPressure Filter KMnO4 Flash Mix ? WWTP Effluent Contact TimeVessel WasteBackwash Discharge DecantRecycle Solids to Avon Plant To

  14. Option 1: Green Sand Filtration • effluent / split flow • fractional treatment / on demand • Option 2: MAOA • effluent / split flow • fractional treatment / on demand Both options require significant capital and time to implement Enhanced Cu Removal at the WWTP

  15. Option 3: Manganese Oxide Co-Precipitation • simple chemical addition • utilizes existing processes for removal • easily implemented • on demand Jar testing initiated at HDR’s Water Quality Lab Enhanced Cu Removal at the WWTP

  16. Lab Testing

  17. Jar Testing

  18. High Tech Lab Equipment

  19. Chemical Addition Effective in Lab • Can reduce Cu from 500 ug/L to 5 ug/L in clean water with dose as low as 3 mg/l as Mn • Wastewater requires higher doses due to competing sorption of organics • Dose decreases as organics decrease • MnSO4 to KMnO4 ratio of 2:1

  20. Testing Priority • 1. Full-Scale test of the Manganic Oxide / Co-Precipitation Option • Minimal equipment requirements • Mobile chemical feeds • Green sand filtration (50 gpm pilot) • MetClean (3 gpm pilot) • Last 2 options to be implemented if Full-Scale test unsuccessful

  21. Potential Application Points • Pre Aeration • Eliminated after one day of testing • High level of competing organics • Pre Nitrification • Eliminated to avoid precipitation in nitrification cells • Post Aeration • Add at outlet of aeration basins • Utilizes secondary clarifier for removal of precipitate

  22. Test Protocol • Add to aeration basin outlet • Target dose of 5 mg/L as Mn • 2:1 ratio of manganese sulfate to permanganate • Adjust dose based on results

  23. Chemical Feed Equipment

  24. Feed Lines • Plugged line in less than 8 hours • Repiped to combine just above application point

  25. Feed Point

  26. Mn Testing

  27. Results • Dose ranged from 5.9 to 11.6 mg/L • MnSO4 to KMnO4 ratio ranged from 1.5 to 3.4 • Storage tank size was not what was ordered (actually 245 gallons instead of 275 gallons) • First set of scales used to measure chemicals inaccurate • Chemicals must be combined as close to application point as possible • High levels of Mn colored plant effluent

  28. Effluent Color at high Mn Levels

  29. Color • Polymer addition ineffective in removing color • Lab tests indicate coprecipitating with 2-3 mg/L of iron effective in removing color Filtered Settled (w/polymer on left)

  30. Full Scale Test Results

  31. Implementation Costs • Capital cost estimated at $82,000 • Operating costs • Based on 1.8 mgd

  32. Conclusions • Co-precipitation can be effective in removing copper • Further testing needed to refine dosage • Color issue must be addressed to implement

  33. Current Status • Plant discontinued testing due to commissioning of new UV system • ERWSD now adding corrosion inhibitor to drinking water which has lowered influent Cu levels below discharge limit

  34. ~Acknowledgements~ Eagle River Water and Sanitation DistrictJim EdwardsChuck SteppCandy Burbridge HDR Engineering, Inc.Steve Reiber Sid Hendrickson

  35. 2002 RMSAWWA / RMWEAJoint Annual Conference Copper Removal at the Vail Wastewater Treatment Plant Eagle River Water and Sanitation DistrictHDR, Inc.

  36. Option 1: MAOA • Treat entire flow stream • Reduce copper to < 25 µg/L • Costs: O&M ≈ $0.5/1000 gal. • Capital ≈ ? • Option 2: Green Sand Filtration • Treat entire flow stream • Reduce copper to < 10 µg/L • Costs: O&M ≈ $0.25/1000 gal. • Capital (1 MGD) ≈ $400,000 Controlling Copper at the Well Head

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