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Indirect Potable Reuse at Cottonwood Water and Sanitation District

Indirect Potable Reuse at Cottonwood Water and Sanitation District. Rick Arber, Ben Johnson Richard P. Arber Associates Pat Mulhern MRE. Types of Reuse. Agricultural & Industrial. Exchanges Recycle-process, cooling. Municipal. Urban Landscape Irrigation Indirect Potable Use

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Indirect Potable Reuse at Cottonwood Water and Sanitation District

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  1. Indirect Potable Reuse at Cottonwood Water and Sanitation District Rick Arber, Ben Johnson Richard P. Arber Associates Pat Mulhern MRE

  2. Types of Reuse

  3. Agricultural & Industrial • Exchanges • Recycle-process, cooling

  4. Municipal • Urban Landscape Irrigation • Indirect Potable Use • Direct Potable Reuse

  5. WTP WWTP AWT Non-Potable Reuse

  6. WTP WWTP WTP WWTP Unplanned Indirect Potable Reuse

  7. Aquifer WTP WWTP AWT Planned Indirect Potable Reuse

  8. WTP WWTP Direct Potable Reuse AWT

  9. Cottonwood Water and Sanitation District

  10. CWSD…. • Formed in 1981 • 1200 Acres of residential and commercial development • Slow development in 1980s • Rapid development in 1990s

  11. Water Supplies • Deep wells (Dawson, Denver, Arapahoe, Laramie Fox Hills) • Cherry Creek alluvium • Wastewater • ACWWA Lone Tree Creek WWTP

  12. Deep Wells • 995 acre Feet • Fe, Mn, H2S • Alluvial Water • 141 acre feet senior rights • 585 acre feet junior rights • Upstream discharges (Pinery, Parker, Stonegate)

  13. Deep Wells • non-renewing • draw down/capacities • require treatment • Alluvial Wells • renewable • high capacity • require treatment

  14. Alternatives • Deep Wells • Non-renewing; eventual depletion • Additional wells need with draw down • Limited production • Treatment required

  15. Alternatives • Dual Distribution $$$ • Import Groundwater $$$

  16. Alternatives • Reuse Renewable supply Extend deep groundwater Greater production

  17. Centralized vs. Decentralized Treatment • Capital cost 10% less for centralized treatment. • O&M cost similar for centralized treatment and decentralized. • Centralized treatment easier to operate.

  18. The Plan

  19. Average daily demand 2 mgd • Maximum daily demand 6 mgd

  20. Treatment • Cartridge Filters • UV? • Anti-scalant • Nanofiltration • Degassifier • pH adjust • Alkalinity • Chlorine

  21. Indirect Potable Reuse • Multiple Barriers • WWTP/AWT • Alluvium (3000 ft.,~ 1.5 years travel) • Membrane water treatment (100%) • Final disinfection

  22. Concentrate Disposal • Cherry Creek Basin • PO4 • Split Flow • ACWWA WWTP (base flow) • Irrigation

  23. Pilot Testing

  24. Objectives • Evaluate effectiveness of NF on raw water • Determine design criteria • Evaluate fouling potential • Evaluate feed, permeate, and concentrate water quality • Select appropriate membrane

  25. Pilot Testing Plan • Three month duration • Test different membranes • Sample water quality 6 times • At beginning and end of each membrane test • Operate at 83% recovery • 2.0 gpm permeate • 0.5 gpm concentrate

  26. Performance • Tested two membranes • Osmonics • Filmtec (2 month test) • Added anti-scalant chemical(Pro Treat) • Potential for sulfate precipitation reduced • No significant fouling was observed

  27. Results • Both membranes performed well • Osmonics tighter - higher driving pressure • Filmtec looser - lower contaminant rejection • Average Rejection • TDS • Osmonics 68% Filmtec 62% • Hardness • Osmonics 84% Filmtec 69% • TOC successfully rejected by both membranes (BDL)

  28. Project Costs • Treatment • $9.3 million • Ancillary facilities • $2.3 million

  29. Public Education Program • Consultant • Literature • CDPHE involvement • Public meetings

  30. Schedule • Predesign underway • Design 2003 • Construct 2004 • Start up 2005

  31. Conclusions • NF effective in removing TOC • Multiple barriers provide public health protection • Indirect potable reuse is viable, cost effective water supply for CWSD • Public support is needed

  32. Questions?

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