Desalination

Report
Seawater Desalination and
Water Supply Reliability
in Marin County
Louis Armstrong, URS Corporation
MMWD
• Founded in 1912 – California’s first
municipal water district
• Serves 185,000 residents of Central
and Southern Marin County
• Primary supply is local reservoirs (5 on
Mt. Tamalpais watershed, 2 in West
Marin)
Current MMWD Supplies
Recycled
2%
Russian River
(via NMWD )
26%
Reservoirs
72%
Marin’s Demand for Water
35,000
1987 Demand
30,000
Operational Yield†
25,000
20,000
15,000
10,000
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
5,000
Projected Demand Increase
(120AF Per Year)
35000
Yield
30000
25000
20000
15000
10000
5000
0
2002
2005
2010
2015
2020
Utilizing North Marin Pipeline
Projected “Decay” of Excess Delivery Capacity
Loss of 2,300AF
by 2015
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
20
15
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
Projected 2015 Scenario
• Current supply deficit: 3,200AF
• Demand increase: 1,560AF
• Projected loss of NMWD capacity:
2,300AF
• Total projected deficit:
7,060 AF
Possible Solutions: Soft Path
• Increased Conservation: 2,000 AF
• Increased Recycling: 1,800-2,100 AF
• Adjust Service Levels: 869 AF
• TOTAL: 4,669 to 4,969 AF
So what about Desalination…..
The Process
Desalination By Reverse Osmosis
• 2 gallons of seawater
•
•
= 1 gallon of high
quality drinking water
Pre-treatment and RO
removes
contaminants,
including mercury and
other contaminants in
the Bay
MMWD will use “dual
pass” RO
Reverse Osmosis

Flow at the Membrane
Effectiveness of Reverse Osmosis
World-Wide Installed Capacity
Desalination Highlights
• Advantages
– reliability (drought
proof)
– independence/selfsufficiency
– possibly smaller
environmental
footprint
– high quality water
• taste test
• Challenges
– siting of plant
– energy consumption improved technology,
green power options,
environmental
management system
plan
– discharge (CMSA)
– intake (Rod & Gun
Club pier)
– sludge disposal
Preferred Plant Location
Option for Discharge of Brine
Mix with existing WWTP outflow
Considerations:
– Need existing outfall with sufficient capacity
– Potential to reduce dilution due to buoyancy in
receiving water, or increase momentum mixing
– Potential for in-pipe dilution of constituents in
wastewater
Next Steps...
• Draft EIR released : Late Summer
2004
• Certification of the EIR : Late 2004

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