recycled water: quantifying some of its’ hidden advantages gary wolff, p.e., ph.d. principal...
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Recycled Water: Quantifying Some of Its’
Hidden Advantages
Gary Wolff, P.E., Ph.D.Principal Economist &
Engineer9 March 2006
![Page 2: Recycled Water: Quantifying Some of Its’ Hidden Advantages Gary Wolff, P.E., Ph.D. Principal Economist & Engineer 9 March 2006](https://reader035.vdocuments.site/reader035/viewer/2022081517/5697c01d1a28abf838cd05ab/html5/thumbnails/2.jpg)
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The Advantages, Today:
• Yield Reliability
• Cost Stability
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Yield Reliability: Acknowledgments and Disclaimers
• This Work Was Funded by the Bureau of Reclamation; Thanks to Steve Kasower and Kevin Price
• Thanks Also to Mark Buehler, Tom Chesnutt, Michael Hanemann, Michael Kiparsky, Bob Raucher, and Bob Wilkinson, for Sharing Their Thinking on This Topic
• Disclaimer: The Following Results Are A Mix of Fact and Fiction
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A Fictional Water Supply Problem
Water and Financial Managers Face A Similar Problem:
How To Deliver Water or Pension Checks Year After Year, Reliably, Despite Weather or Stock Market Uncertainty
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Satisfying Growth In Demand:The Old Math
DTDE
2 S.D.
Annual Reservoir Releases Available For Use (units per year)
% of Years
SN
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Satisfying Growth in Demand: Portfolio Math
• On Previous Slide, SN = ( DT – DE ) Leaves Out Uncertainty in Supply Sources
• Should Write: SN = ( DT – DE ) + SR
• Where SR Is Insurance Against Uncertainty
• And SR Depends On:
– Variability of Existing (E) and New (N)– Correlation Between E and N Sources
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Comparing Some Fictional Options
Source of SN S.D. of N
Correlation Of E & N
SN / Unit of Growth
Desalinated or Recycled Water
0% 0.0 1.00
Import X 10% 1.0 1.25
Import Y 20% 0.8 1.55
Landscape Use Efficiency
10% -1.0 0.85
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0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
Desalinated orRecycled Water
Import X Import Y Landscape UseEfficiency
Do
llars
Per
Un
it
Average Unit Costs Constant-Reliability Unit Costs
Adjusting To Achieve Constant-Reliability Can Change Decisions
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Cost Stability• Recycled Water Is NOT Very Energy Intensive• Its Variable Costs Are A Smaller Percent of
Operating Costs Than Seawater Desalination• Consequently, Energy Price Increases And
Volatility Affect The Cost of Recycled Water Less Than The Cost of Desalinated Water
• This Reduced Exposure to Energy Price Increases And Volatility Is A Quantifiable Advantage
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Recycled Water Is NOT Very Energy Intensive (SDCWA Data)
0500
100015002000
25003000350040004500
ColoradoRiver
Aqueduct
State WaterProject
Groundwater ReclaimedWaste Water
SeawaterDesalination
BrackishWater
Desalination
Ocean-Towed Water
Bags
Ener
gy In
tens
ity (k
Wh/
AF)
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Impact of Energy Price Changes on Water Cost Over Time (LA Area)
0
0.5
1
1.5
2
2.5
31971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Year
Rela
tive C
ost
in L
A (
No
min
al
$)
Recycled Water Desalinated Seawater Gravity Surface Water
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Impact of Energy Price Changes on Water Cost Over Time (SF Area)
0
0.5
1
1.5
2
2.5
3
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Year
Rela
tive C
ost
in S
F (
No
min
al
$)
Recycled Water Desalinated Seawater Gravity Surface Water
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ConclusionsRecycled Water is Even
Better Than You Think! However, We Need Case
Studies to Fully Quantify Hidden Advantages
Gary Wolff, P.E., [email protected]