Indirect Potable Reuse at Cottonwood Water and Sanitation District

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
Non-Potable Reuse
6
Unplanned Indirect Potable Reuse
7
Planned Indirect Potable Reuse
8
Direct Potable Reuse
AWT
9

• Cottonwood Water and Sanitation District

10
(No Transcript)
11

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

12

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

13

• 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)

14

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

15
(No Transcript)
16
Alternatives

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

17
Alternatives

• Dual Distribution
• Import Groundwater

18
Alternatives

• Reuse
• Renewable supply
• Extend deep groundwater
• Greater production

19
Centralized vs. Decentralized Treatment

• Capital cost 10 less for centralized treatment.
• OM cost similar for centralized treatment and
  decentralized.
• Centralized treatment easier to operate.

20
The Plan
21

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

22
(No Transcript)
23
Treatment

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

24
Indirect Potable Reuse

• Multiple Barriers
• WWTP/AWT
• Alluvium (3000 ft., 1.5 years travel)
• Membrane water treatment (100)
• Final disinfection

25
Concentrate Disposal

• Cherry Creek Basin
• PO4
• Split Flow
• ACWWA WWTP (base flow)
• Irrigation

26
Pilot Testing
27
Objectives

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

28
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

29
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

30
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)

31
Project Costs

• Treatment
• 9.3 million
• Ancillary facilities
• 2.3 million

32
Public Education Program

• Consultant
• Literature
• CDPHE involvement
• Public meetings

33
Schedule

• Predesign underway
• Design 2003
• Construct 2004
• Start up 2005

34
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

35

• Questions?

36
Concentrate Disposal

• 15 of feed flow (1.8 mgd)
• PO4 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)

37
Concentrate Disposal

• Base flow to Lone Tree WWTP
• Effluent PO4lt 0.05 mg/L
• PO4 removed from basin 1190 lb./year
• Balance to irrigation ( 115 acres)
• Irrigation PO4 1.2 mg/L