Transcript No Slide Title

Arber
Indirect Potable Reuse at
Cottonwood Water and Sanitation
District
Rick Arber, Ben Johnson
Richard P. Arber Associates
Pat Mulhern
MRE
Cottonwood Water & Sanitation District
September 2002
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Cottonwood Water & Sanitation District
Types of Reuse
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Agricultural & Industrial
• Exchanges
• Recycle-process, cooling
Cottonwood Water & Sanitation District
September 2002
Municipal
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• Urban Landscape Irrigation
• Indirect Potable Use
• Direct Potable Reuse
Cottonwood Water & Sanitation District
September 2002
Non-Potable Reuse
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WTP
WWTP
AWT
Cottonwood Water & Sanitation District
September 2002
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Unplanned Indirect Potable
Reuse
WTP
WWTP
WTP
WWTP
Cottonwood Water & Sanitation District
September 2002
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Planned Indirect Potable Reuse
Aquifer
WTP
WWTP
AWT
Cottonwood Water & Sanitation District
September 2002
Direct Potable Reuse
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WTP
WWTP
AWT
Cottonwood Water & Sanitation District
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Cottonwood Water and Sanitation
District
Cottonwood Water & Sanitation District
September 2002
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Cottonwood Water & Sanitation District
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CWSD….
• Formed in 1981
• 1200 Acres of residential and
commercial development
• Slow development in 1980s
• Rapid development in 1990s
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September 2002
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• Water Supplies
• Deep wells (Dawson, Denver,
Arapahoe, Laramie Fox Hills)
• Cherry Creek alluvium
• Wastewater
• ACWWA Lone Tree Creek WWTP
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• 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)
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September 2002
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• Deep Wells
– non-renewing
– draw down/capacities
– require treatment
• Alluvial Wells
– renewable
– high capacity
– require treatment
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CWSD SAFETY FACTOR DEMAND AND AVERAGE YEAR SUPPLY
vs. TIME
Demand/Supply (AF/YR)
3000
Yearly
Demand *
2500
Average
Year Supply
2000
1500
Linear
(Yearly
Demand *)
1000
500
* Includes 20%Additional Safety Factor Above Projected Demand
0
1995
2000
2005
2010
2015
2020
Year
Cottonwood Water & Sanitation District
September 2002
Alternatives
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• Deep Wells
– Non-renewing; eventual depletion
– Additional wells need with draw
down
– Limited production
– Treatment required
Cottonwood Water & Sanitation District
September 2002
Alternatives
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• Dual Distribution $$$
• Import Groundwater $$$
Cottonwood Water & Sanitation District
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Alternatives
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• Reuse
Renewable supply
Extend deep groundwater
Greater production
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September 2002
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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 District
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Cottonwood Water & Sanitation District
The Plan
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• Average daily demand 2
mgd
• Maximum daily demand
6 mgd
Cottonwood Water & Sanitation District
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Cottonwood Water & Sanitation District
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Treatment
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Cartridge Filters
UV?
Anti-scalant
Nanofiltration
Degassifier
pH adjust
Alkalinity
Chlorine
Cottonwood Water & Sanitation District
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Indirect Potable Reuse
• Multiple Barriers
– WWTP/AWT
– Alluvium (3000 ft.,~ 1.5
years travel)
– Membrane water
treatment (100%)
– Final disinfection
Cottonwood Water & Sanitation District
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Concentrate Disposal
• Cherry Creek Basin
– PO4
• Split Flow
– ACWWA WWTP (base flow)
– Irrigation
Cottonwood Water & Sanitation District
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Cottonwood Water & Sanitation District
Pilot Testing
September 2002
Objectives
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• Evaluate effectiveness of NF on
raw water
• Determine design criteria
• Evaluate fouling potential
• Evaluate feed, permeate, and
concentrate water quality
• Select appropriate membrane
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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 District
September 2002
Performance
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• Tested two membranes
– Osmonics
– Filmtec (2 month test)
• Added anti-scalant chemical(Pro Treat)
– Potential for sulfate precipitation reduced
• No significant fouling was observed
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Results
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• 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)
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Project Costs
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• Treatment
– $9.3 million
• Ancillary facilities
– $2.3 million
Cottonwood Water & Sanitation District
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Public Education Program
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Consultant
Literature
CDPHE involvement
Public meetings
Cottonwood Water & Sanitation District
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Schedule
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Predesign underway
Design 2003
Construct 2004
Start up 2005
Cottonwood Water & Sanitation District
September 2002
Conclusions
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• 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 District
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• Questions?
Cottonwood Water & Sanitation District
September 2002