Water treatment options - Counties eye desalination
Article Last Updated: Wednesday, Aug 17, 2005 - 12:14:54 am PDT
A technician programs equiptment at the Marin Municipal Water District's pilot desalination plant. (Courtesy Photo)
Water treatment options - Counties eye desalination
By Barry Eberling
FAIRFIELD - It's an feat of alchemy that in semi-arid, fast-growing California rivals turning lead into gold.
Technology holds the promise of economically turning salty water into fresh water. Brackish Suisun Bay and San Pablo Bay could become Solano County's newest drinking water sources, and massive ones at that.
Someday.
"We think the technology will improve and the cost of desalinization will go down over time," Solano County Water Agency General Manager David Okita said. "We're in a position to be able to wait."
Solano County cities and farms face water shortages only during prolonged drought. They have water rights from Lake Berryessa reservoir in Napa County and the Sacramento San Joaquin Delta. They use groundwater.
But Solano County is expected to be the Bay Area's fastest-growing county in coming decades. As the population continues to swell, the brackish waters of Suisun Bay and San Pablo Bay could become more tempting.
The water agency decided to look at desalination in the future, not right now, Okita said.
Other nearby counties are looking at desalinization now. They are doing pioneering work that might someday serve Solano County.
The Marin Municipal Water District built a $1.2 million test desalinization plant it plans to operate for nine months. This plant near the Richmond Bridge takes the waters of San Francisco Bay, cleanses it of impurities and removes the salt.
District officials realize some residents might be put off by the thought of drinking the murky bay waters. Officials say the cleaned-up water will be as pure as bottled water.
The district keeps a cooler with the water available at its Corte Madera office, so passersby can give it a try.
Marin's pilot plant forces the brackish bay water through a semi-permeable membrane. The holes in the membrane are big enough for water molecules, but too small for salt molecules. This results in fresh water, most of which goes back to the bay.
"We're using it for a test," district spokeswoman Libby Pischel said. "We're not using it as part of our water supply."
Whether Marin pushes forward with a full-scale desalination plant remains to be seen. But that area is in greater need of new water supplies than Solano County.
"We would have to have very extreme rationing in the second year of a drought," Pischel said.
Four other Bay Area water agencies serving Contra Costa County, Alameda County, Santa Clara County and San Francisco County have teamed up to look at desalination. Possible plant sites include Crockett along the Carquinez Strait and Pittsburg along Suisun Bay. Plants could provide up to 120 million gallons of water daily - enough for about 134,000 households of four.
"For us, the big issue is we don't have enough water in drought years," said Jeff Becerra of the East Bay Municipal Utility District.
But using desalinated water comes with a price. Marin estimates a full-scale plant could cost $60 million, with another $35 million going toward a distribution system. Newark in Alameda County has a $20 million plant that removes salt from brackish groundwater.
There are also environmental challenges to desalination.
Desalination plants can suck in fish and larvae along with salt water. Jared Huffman doesn't expect this to be a problem with the Marin plant. Huffman is president of the Marin water district board and is an attorney with the National Resources Defense Council.
The plant Marin is contemplating will be small enough to take in water at a low velocity, Huffman said.
"If you held your hand up to the screen, you literally wouldn't feel the water moving," he said.
Desalination creates fresh water. It also creates a brine of salt and heavy metals that has no use. Put the brine back into the bay at heavy concentrations and it hurts fish and aquatic organisms, a BCDC desalination report says.
A plant along the coast can use a pipe to disperse the brine in the ocean, Okita said.
"I'm not sure you can do that in Suisun Bay or San Francisco Bay," Okita said.
One possibility is to build a desalination plant next to a power plant or sewer plant. Then the brine can be mixed with discharge water, diluting it, the BCDC report said.
The Marin pilot plant simply remixes its fresh water with the brine and returns it to the bay. But that won't work once the fresh water is used by residents.
Marin proposes to mix brine with treated sewage water, Huffman said. This will create a mixture that has the same salinity as the bay.
The Marin pilot plant will help identify what steps are needed to protect the environment, he said.
"You want to go carefully into something like this that would be a first in the bay," Huffman said. "You want to give it a good, honest look in terms of its potential environmental impact."
One thing seems certain: Desalination will continue to get a serious look in California. The state in its 2005 Water Plan Update has a chapter on desalination. Desalting seawater creates a new water supply, the plan said.
Someday, Solano County may tap into the huge, brackish water supply at its doorstep.
Reach Barry Eberling at 425-4646 Ext. 232 or at beberling@dailyrepublic.net.
A technician programs equiptment at the Marin Municipal Water District's pilot desalination plant. (Courtesy Photo)
Water treatment options - Counties eye desalination
By Barry Eberling
FAIRFIELD - It's an feat of alchemy that in semi-arid, fast-growing California rivals turning lead into gold.
Technology holds the promise of economically turning salty water into fresh water. Brackish Suisun Bay and San Pablo Bay could become Solano County's newest drinking water sources, and massive ones at that.
Someday.
"We think the technology will improve and the cost of desalinization will go down over time," Solano County Water Agency General Manager David Okita said. "We're in a position to be able to wait."
Solano County cities and farms face water shortages only during prolonged drought. They have water rights from Lake Berryessa reservoir in Napa County and the Sacramento San Joaquin Delta. They use groundwater.
But Solano County is expected to be the Bay Area's fastest-growing county in coming decades. As the population continues to swell, the brackish waters of Suisun Bay and San Pablo Bay could become more tempting.
The water agency decided to look at desalination in the future, not right now, Okita said.
Other nearby counties are looking at desalinization now. They are doing pioneering work that might someday serve Solano County.
The Marin Municipal Water District built a $1.2 million test desalinization plant it plans to operate for nine months. This plant near the Richmond Bridge takes the waters of San Francisco Bay, cleanses it of impurities and removes the salt.
District officials realize some residents might be put off by the thought of drinking the murky bay waters. Officials say the cleaned-up water will be as pure as bottled water.
The district keeps a cooler with the water available at its Corte Madera office, so passersby can give it a try.
Marin's pilot plant forces the brackish bay water through a semi-permeable membrane. The holes in the membrane are big enough for water molecules, but too small for salt molecules. This results in fresh water, most of which goes back to the bay.
"We're using it for a test," district spokeswoman Libby Pischel said. "We're not using it as part of our water supply."
Whether Marin pushes forward with a full-scale desalination plant remains to be seen. But that area is in greater need of new water supplies than Solano County.
"We would have to have very extreme rationing in the second year of a drought," Pischel said.
Four other Bay Area water agencies serving Contra Costa County, Alameda County, Santa Clara County and San Francisco County have teamed up to look at desalination. Possible plant sites include Crockett along the Carquinez Strait and Pittsburg along Suisun Bay. Plants could provide up to 120 million gallons of water daily - enough for about 134,000 households of four.
"For us, the big issue is we don't have enough water in drought years," said Jeff Becerra of the East Bay Municipal Utility District.
But using desalinated water comes with a price. Marin estimates a full-scale plant could cost $60 million, with another $35 million going toward a distribution system. Newark in Alameda County has a $20 million plant that removes salt from brackish groundwater.
There are also environmental challenges to desalination.
Desalination plants can suck in fish and larvae along with salt water. Jared Huffman doesn't expect this to be a problem with the Marin plant. Huffman is president of the Marin water district board and is an attorney with the National Resources Defense Council.
The plant Marin is contemplating will be small enough to take in water at a low velocity, Huffman said.
"If you held your hand up to the screen, you literally wouldn't feel the water moving," he said.
Desalination creates fresh water. It also creates a brine of salt and heavy metals that has no use. Put the brine back into the bay at heavy concentrations and it hurts fish and aquatic organisms, a BCDC desalination report says.
A plant along the coast can use a pipe to disperse the brine in the ocean, Okita said.
"I'm not sure you can do that in Suisun Bay or San Francisco Bay," Okita said.
One possibility is to build a desalination plant next to a power plant or sewer plant. Then the brine can be mixed with discharge water, diluting it, the BCDC report said.
The Marin pilot plant simply remixes its fresh water with the brine and returns it to the bay. But that won't work once the fresh water is used by residents.
Marin proposes to mix brine with treated sewage water, Huffman said. This will create a mixture that has the same salinity as the bay.
The Marin pilot plant will help identify what steps are needed to protect the environment, he said.
"You want to go carefully into something like this that would be a first in the bay," Huffman said. "You want to give it a good, honest look in terms of its potential environmental impact."
One thing seems certain: Desalination will continue to get a serious look in California. The state in its 2005 Water Plan Update has a chapter on desalination. Desalting seawater creates a new water supply, the plan said.
Someday, Solano County may tap into the huge, brackish water supply at its doorstep.
Reach Barry Eberling at 425-4646 Ext. 232 or at beberling@dailyrepublic.net.
posted by Solano EDC at 10:01 AM
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