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Developing a Reclaim Water System for The University of North Carolina at Chapel Hill

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Potential Reuse Demands* vs. Projected Potable Water Demands ... Reclaimed. Potable. Total. Reclaimed. Water. Water. Demand. as % of (mgd) (mgd) (mgd) Total. 2009. 0 ... – PowerPoint PPT presentation

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Title: Developing a Reclaim Water System for The University of North Carolina at Chapel Hill


1
Developing a Reclaim Water System for The
University of North Carolina at Chapel Hill
Big 10 Friends Utility Conference Ames, IA May
2009
2
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4
UNC District Energy Systems

5
Chilled Water System 200 mgy
  • (5) Interconnected Central Plants
  • 50,000 tons installed capacity
  • Serving 145 research and academic buildings

6
Why We Pursued Reclaim
  • Long term stable water
    supply
  • Drought proof
  • Current reclaim supply exceeds our projected
    needs
  • Supply will grow as our loads grow
  • Decouple campus growth from towns water supply
  • Second water source for plants

7
Why We Pursued Reclaim
  • Cost Control
  • Predictable cost of service rate
  • Avoids exposure to seasonal conservation rates
  • Strategic long term investment

8
How We Pursued Reclaim
  • Quality Assessment
  • OWASA/UNC feasibility studies
  • Disinfection Study UNCs Mark Sobsey
  • Pilot plant and tower treatment simulations
  • Follow up testing to confirm pilot results

9
How We Pursued Reclaim
  • Production and Distribution
  • OWASA design / build / operate / maintain
  • UNC reviewed design and cost estimates

10
How We Pursued Reclaim
  • Chiller Plant Systems
  • Maintain fully automated operation
  • Automatic failover to potable
  • Allow blending of potable and reclaim
  • Air gaps added
  • Online quality monitoring

11
Water and Energy Basics
  • Cycles of Concentration make up use/blowdown
    use
  • You may often use system conductivity divided by
    make up conductivity
  • Deposits in machines, condensers or boilers
    increase energy consumption

12
Things to look for in reclaim streams
13
Steps to Evaluate Streams
  • Analyze the sample
  • Model the water against the application
  • Balance the results versus the investment to make
    it work
  • If are large test the results in a pilot
    application

14
Steps to Evaluate Streams
Example of differential bio
  • Risk UNCs own Dr Sobsey reviewed and
    recommended the disinfection process

15
Steps to Evaluate Streams
16
Steps to Evaluate Streams
17
Steps to Evaluate Streams
Water for pilot scale evaluation
18
Results of Pilot Testing and City Water Runs
  • Historical Results
  • MS lt2 mpy to 3
  • Cu lt0.1 mpy to 0.1
  • Study Findings
  • Dispersant and Alkaline Zinc
  • MS 1.1 to 2.5 (localized to 100 mpy)
  • Cu 0.01 to 0.04
  • Dispersant/PSO
  • MS 0.9 to 2.3 (localized to 6)
  • Cu 0.06 to 0.14
  • Transition made on city water due to new zinc
    limitations and to confirm pilot success on
    actual plant
  • MS 0.1 general
  • Cu lt0.1 none

19
Implementation at the Plant
  • Reclaim lines added as tower water make up,
    monitoring placed in line and air breaks added to
    potable make up
  • 3D TRASAR Control
  • Control on active polymer
  • Control inhibitor levels
  • 24/7 Nalco 360 Monitoring Service
  • Ramp Rate Step Changes for conversions
  • Risk Reduction through chlorination

20
We also followed up the pilot testing with
samples during plant run in time
  • We know what the actual plant variances look like
  • Acid to limit alkalinity
  • Chlorine to reduce risk
  • Insulate alum feed to reduce PO4 upsets

21
Reclaim Water
22
General Layout of the Planned Water Reuse System
23
Feasibility Study Results
  • Feasible for use in cooling towers
  • Represented more than 90 of projected demand
  • Feasible for irrigation use, toilet flushing
  • Other uses may also be possible

24
UNCs Peak Demand Ratios are Higher Than Our
System-wide Peaking Ratios
25
2008 Daily Make-up Water Use at UNC Chillers
(not including UNC Hospitals or Cogen)
26
Potential Reuse Demands vs. Projected Potable
Water Demands
Demands shown are for cooling tower make-up
water and irrigation uses, only. Potential
demands may be higher if other uses are met
through reuse. Water reuse may also be a
strategy for meeting Carolina North water needs,
but that potential is not reflected in the above
table.
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28
Deferred Capital Costs
  • Could defer 5 capital projects for several years
    through reuse/conservation
  • Net Present Savings of project deferrals gt
    3,000,000 in next 9 years
  • Potential deferral/reduction in gt 40 million to
    go to Jordan Lake on our own
  • 80,000 ft. of pipe, intake and two pumping
    stations
  • Reduce long-term energy requirements

29
Peak Day Demands No Reuse
30
Reuse Defers WTP Expansion (by about 15 years)
31
Financial Feasibility
  • UNC Funding gt 10,000,000 for Phase I
  • 1.866 million CWMTF grant
  • 0.625 million EPA grant
  • UNC currently pays OWASA 5.85/1,000 gallons for
    all potable water use during May-Sept. and
    3.08/1,000 gallons in all other months
  • Water rates have increased annually

32
Financial Feasibility
  • UNC projects treatment cost at towers to increase
    0.45/1,000 gallons for RCW
  • UNC expects positive ROI in 4 to 10 years
  • Depends on scenarios/demands served

33
In the End
Conclusions Know where you are with respect to
industry standards Evaluate options and required
actions versus payback Set processes in place to
reduce risk with respect to Performance and
Risk Take Action
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