Desalination for Marin County

1
Desalination for Marin County

• Paul Helliker
• General Manager
• Marin Municipal Water District
• North Bay Watershed Association
• April 5, 2007

2
2-Minute History of MMWD Water

• Annual Rainfall 1879 through 2001

1996 Lagunitas Creek Settlement
1971 Measure B Fails
1982 Kent Lake Raised
1960 Nicasio
1992 Measure V Passes
1979 Soulajule
1953 Kent
1977 Richmond Bridge Pipeline
1948 Bon Tempe
1991 Measure W Fails
1918 Alpine
1990 Pilot De-Sal Plant
1976 First Russian River Imports
1912 MMWD formed
3
Current MMWD Supplies
High cost
Supply will decrease 25
Climate uncertainties
4
Projected Supply and Demand
Acre-feet
1987 Demand
35000
Current Yield
30000
Future Yield
25000
20000
15000
10000
5000
0
2002
2005
2010
2015
2020
5
Projected 2020 Scenario

• Current supply deficit 3,200AF
• Demand increase 1,560AF
• Projected loss of NMWD capacity 2,300AF
• Total projected deficit 7,060 AF

6
MMWD Options

• Conservation
• Remains first choice
• Already achieved 25 savings
• BMPs implemented and very aggressive tiered
  rates
• Additional reductions may cost more than other
  options
• Recycling
• Currently have many innovations in place
• Expansion complicated by cost and water quality
  issues
• Imports
• Endangered species protection limitations
• Least costly now likely increase
• Desalination
• Reliable supply
• Cost and energy use are major issues

7
MMWD Plan

• Proximity to infrastructure
• Mix brine with wastewater in existing deep water
  outfall
• Intake water is less saline and is warmer than
  ocean
• No power plant impacts
• Public ownership
• Reduce imports

8
MMWD Desalination Pilot Program EIR

• Nine/Twelve month demonstration and test
• Conventional/MF/UF pretreatment, 4 Reverse
  Osmosis makes
• Chemical, biological testing of water streams
• Dilution modeling
• Fisheries studies
• Entrainment analysis

9
Intake Screening

• Designed to meet Federal and State criteria for
  fish protection
• 3/32-inch openings
• lt0.3 fps velocity
• airburst cleaning
• Located at end of existing 2000-ft pier
• Multiple screens for full-scale facility

10
Reverse Osmosis (RO) Desalination

• Tested four manufacturers
• Three RO elements per train
• Initial problems with non-standard sizes
• All performed acceptably fewer cleanings with
  MF/UF

11
Bay Fish SamplingSummary of Results

• Northern anchovy Pacific herring common in
  midwater trawl
• Bay goby, shiner perch common in otter trawl
• Dungeness crab most common invertebrate
• Species composition similar to CDFG sampling
• Spiny dogfish not collected by CDFG
• Long-term CDFG data can be used in the
  environmental analysis

12
Pilot Plant Entrainment Study

• Measurement of species composition, seasonal
  distribution, and densities of icthyoplankton,
  crab, shrimp, oysters
• Twice monthly for 12 months
• Use Empirical Transport Model, Adult Equivalent
  Loss and Fecundity Hindcast models to estimate
  entrainment impacts

13
Estimated Entrainment
14
Results to Date

• ETM estimates range from 0.02 0.06, well below
  sustainable harvest level of 30-40
• No northern anchovies in source water no ETM
  estimate
• No salmon, steelhead or sturgeon larvae were
  collected

15
Brine Discharge Analysis

• Analyzed near- and far-field dilution of brine in
  sewage effluent
• Brine flows stable, up to 15 MGD
• Sewage highly variable flow 2 100 MGD
• Near field dilutions average 2001, min. of 91
• Far field dilutions in San Rafael Bay of 15001

16
Size of the Initial Mixing Zone
Worst Case 650m x 250m Mean 30m x 15m
17
Brine Mixture Bioassays

• Acute bioassays on mysid shrimp, topsmelt, marine
  algae at 79, 27 and 5 brine
• No significant impacts
• Chronic bioassays on giant kelp, bay mussel,
  inland silverside at 79 and 27 brine
• No significant impacts under EPA protocol
  (correct salinity)
• Sublethal impacts for high-brine mix
• No major differences from sewage effluent alone

18
Water Supply Analysis

• Testing for
• 100 Regulated compounds or compounds that require
  monitoring
• 250 non-regulated compounds
• An additional 100 non-regulated compounds
  specific to SF Bay (incl. flame retardants, algal
  toxins)
• E-screen bioassay
• 6,000 Data Points to Evaluate Water Quality and
  Treatment Performance

19
Desalinated Water Quality Results
Detailed List of Constituent Sample Results
Available
Constituents Maximum Contaminant Level (MCL)a SF Bay Watera Desalinated Watera Existing MMWD Sourcesa
Sodium N/A 7,100 21 18 20
Chloride 250b 12,000 20 8 21
Total Organic Carbon (TOC) 2c 0.86 ND 1 2
Boron 1d 2.3 0.2 ND 0.28
Ethylene Dibromide 0.00005 0.00002e ND ND
Mercury 0.002 ND 0.0003e ND
a - ppm b Federal Secondary (aesthetic)
Standard c based on MMWD source water quality d
CA DHS notification level e 4 of 5 samples
tested non-detect
20
Energy for Desalting Seawater is Similar to
Common Appliances
On average, MMWD households use 270 gallons of
water per day
81 Watts 1.9 kWh/day
At 7.15 kWh/1000 gal seawater desalination
requires only 1.9 kWhr/day of power to produce
270 gallons per day.
21
Desal would be approx. 0.7 to 3 of Annual Marin
Energy Use
From California Energy Commission for year 2000
22
Desal Energy is like an extra lightbulb in every
Marin home

• Average operation would be like an extra compact
  fluorescent bulb on all the time
• Drought operation would be like a standard 100-W
  bulb on all the time
• MMWD will be considering renewable power to
  supply this energy need

23
Cost of Desalination Option

• Desalination facility 81-121 million
• Non-construction costs (permitting, construction
  management, etc.) 7-10 million
• In-system distribution improvements (Phases IV
  and V) 22 - 42 million
• Total 110 - 173 million
• Annual operating costs 4 12 million
• Normalized cost 2,433 - 2,023 per acre-foot