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Desalination Boom Nears for Arid California, but Obstacles Remain

Despite lengthy approval and permitting processes, California is the likely bellwether for the future of seawater desalination in the United States

By Sara Stroud

Dec 15, 2010

Editor's Note: This is the first in a three-part series on the development of seawater desalination plants in California and other drought-prone regions, looking at the environmental and economic challenges involved.

When the tiny coastal town of Sand City, Calif., fired up its desalination plant earlier this year, it became the first city in the state to tap the Pacific Ocean to provide drinking water for its residents through a full-scale desalination plant.

And it won't likely be the last. About 20 proposed plants up and down the California coast are wending their way through lengthy approval and permitting processes, as municipalities and water districts look for ways to meet future water needs of a thirsty state.

California's communities are hardly alone. Thousands of facilities around the world are using a range of technologies to remove salt from water, while hundreds of desalination plants in the U.S. treat brackish water. Still, obstacles to their widespread use remain.

In California, high price tags and potential environmental impacts have drawn criticism and delayed projects. But observers say that Sand City's solution may pave the way for a boom in projects, making the Golden State a likely bellwether for the future of seawater desalination in the United States.

"Sand City is pretty monumental," said Timothy Dyer, chief technology officer for San Leandro, Calif.-based , which makes devices for use in reverse osmosis desalination plants, including Sand City's and about 70 percent of such plants worldwide.

"It's a good indication of what we can expect," Dyer continued. "We think [desalination plants] will be more accepted once they get started in California."

But getting started is no small task. California is an extreme case in water-related matters, due to inadequate water supplies, aging infrastructure, an expanding population and the complicated politics and economics involved there in moving water around the state.

Further, while desalination could offer a way to meet water needs and safeguard against shortages, some observers say it could also aggravate climate change. 

In California, where climbing temperatures are expected to decrease snow pack and therefore water supplies, the 20 or so proposed desalination plants could meet about 6 percent of the state's overall water needs.

Energy-Intensive Process

But the electricity required to operate energy-hungry plants means an increase in carbon emissions. Some fear this may harm efforts to meet the state's ambitious greenhouse gas reduction targets. 

"Desalination is an energy-intensive process," said Heather Cooley, a senior research associate at the , an Oakland, Calif.-based research group that focuses on water issues, including desalination. One key to both minimizing the environmental impacts of desalination and making it economically feasible is reducing the amount of energy needed to fuel the process.

Energy makes up about 40 percent of desalination costs. For reverse osmosis plants, which drive seawater through a semi-permeable membrane that separates salt from water, much of that energy goes to pressurizing water to push it through the reverse osmosis membrane. Most of California's proposed plants, including the Sand City facility, are of this type.

Currently, efficient reverse osmosis desalination plants use about 2.5 kilowatts of electricity to produce one cubic meter of water.

Lisa Henthorne, director of the , a nonprofit group based in Topsfield, Mass., said that the industry is aiming to bring that number down to about 1.8 kilowatts through increased efficiencies in the desalination process.

But that could still be too high for California. Meeting the state's water needs is already an energy-intensive undertaking. The water sector accounts for about 20 percent of the state's electricity demand, according to figures.

Lawsuits and Permitting Delays

Errors in Sara Stroud's article

There are a number of errors in Sara Stroud's article about desalination that need to be corrected, and I would appreciate her taking the time to do so.

 First of all, Sand City does not have the first desalination plant in California.  Desalination has been used for decades in locations such as Avalon on Santa Catalina Island, in Fremont by the Alameda County Water District, and in multiple other locations.  And the desalination facility in Monterey County that will allow the reduction in use of Carmel River water will be operated by the Marin Coast Water District, with its partners California American Water and the Monterey COunty Water Resources Agency.

 In Marin County, the voters have not approved a desalination facility.  What they approved is the ability of the Marin Municipal Water District to continue to develop the design and permitting requirements of a desalination facility that would be brought to voters for approval sometime in the future, if there is a need for the facility.  The power requirements cited of 10 million kWh per year are accurate for a 5 million gallon per day facility, but the 77 million kWh per year cited is the energy requirement for a 15 MGD facility under drought conditions - a facility that has not been proposed for Marin County.  Lastly, the energy figures cited for Marin County are off by 3 orders of magnitude - Marin County uses 1.4 BILLION kWh of electricity annually, making the proposed desalination facility a small addition to that demand (less than 1%).

 These facts are important because desalination has been controversial in Marin County and in California, in large part because of energy requirements.  But the Carlsbad plant will be carbon neutral, and the proposed plant in Marin County would be run completely by renewable energy, thus causing no increment in greenhouse gas emissions.

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