Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Indirect Potable Reuse at Cottonwood Water and Sanitation District Rick Arber, Ben Johnson Richard P. Arber Associates Pat Mulhern MRE

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Types of Reuse

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Agricultural & Industrial Exchanges Recycle-process, cooling

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Municipal Urban Landscape Irrigation Indirect Potable Use Direct Potable Reuse

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber WTP WWTP AWT Non-Potable Reuse

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Unplanned Indirect Potable Reuse WTP WWTP WTP WWTP

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Planned Indirect Potable Reuse WTPWWTP AWT Aquifer

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Direct Potable Reuse WTP WWTP AWT

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Cottonwood Water and Sanitation District

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber CWSD…. Formed in Acres of residential and commercial development Slow development in 1980s Rapid development in 1990s

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Water Supplies Deep wells (Dawson, Denver, Arapahoe, Laramie Fox Hills) Cherry Creek alluvium Wastewater ACWWA Lone Tree Creek WWTP

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Deep Wells –995 acre Feet –Fe, Mn, H 2 S Alluvial Water –141 acre feet senior rights –585 acre feet junior rights –Upstream discharges (Pinery, Parker, Stonegate)

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Deep Wells –non-renewing –draw down/capacities –require treatment Alluvial Wells –renewable –high capacity –require treatment

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Alternatives Deep Wells –Non-renewing; eventual depletion –Additional wells need with draw down –Limited production –Treatment required

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Alternatives Dual Distribution $$$ Import Groundwater $$$

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Alternatives Reuse Renewable supply Extend deep groundwater Greater production

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber 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.

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber The Plan

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Average daily demand 2 mgd Maximum daily demand 6 mgd

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Treatment Cartridge Filters UV? Anti-scalant Nanofiltration Degassifier pH adjust Alkalinity Chlorine

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Indirect Potable Reuse Multiple Barriers –WWTP/AWT –Alluvium (3000 ft.,~ 1.5 years travel) –Membrane water treatment (100%) –Final disinfection

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Concentrate Disposal Cherry Creek Basin –PO4 Split Flow –ACWWA WWTP (base flow) –Irrigation

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Pilot Testing

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Objectives Evaluate effectiveness of NF on raw water Determine design criteria Evaluate fouling potential Evaluate feed, permeate, and concentrate water quality Select appropriate membrane

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber 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

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber 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

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber 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)

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Project Costs Treatment – $9.3 million Ancillary facilities – $2.3 million

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Public Education Program Consultant Literature CDPHE involvement Public meetings

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Predesign underway Design 2003 Construct 2004 Start up 2005 Schedule

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber 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

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Questions?

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Concentrate Disposal 15% of feed flow (1.8 mgd) [PO 4 ] ~ 1.2 mg/L Annual average flow 1/3 max day (0.6 mgd) Base flow (in-house) 57% of annual demand (0.34 mgd) Irrigation 43% of annual demand (0.26 mgd)

Cottonwood Water & Sanitation DistrictSeptember 2002 Arber Concentrate Disposal Base flow to Lone Tree WWTP –Effluent PO 4 < 0.05 mg/L –PO 4 removed from basin 1190 lb./year Balance to irrigation (~ 115 acres) –Irrigation PO 4 ~ 1.2 mg/L