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California Turning to Desalination Plants, but Face Criticism on Environment and Cost


Wall Street Journal
January 17, 2008


Water-short California’s search to satisfy its thirst is beginning to focus on
a controversial source — the Pacific Ocean. In November, Connecticut-based
Poseidon Resources Corp. won a key regulatory approval to build a $300 million
water-desalination plant in Carlsbad, north of San Diego. The facility would
be the largest in the Western Hemisphere, producing 50 million gallons of
drinking water a day, enough to supply about 100,000 homes.

Taking the salt out of seawater is a common way to produce drinking water in
the Middle East and in other arid regions. World-wide, 13,080 desalination
plants produce more than 12 billion gallons of water a day, according to the
International Desalination Association.

But it has been less successful in the U.S. Desalination is more expensive
than traditional sources, and critics say it harms the ocean. In 1992, Santa
Barbara, Calif., shuttered a small plant after three months when rain
replenished the county’s main water sources. At a plant near Tampa, Fla., that
Poseidon was also involved in, technical glitches increased the water’s cost
and, when it opened in 2003, initially limited output to less than a third of
the projected 25 million gallons a day.

Southern California water officials say conditions have changed. Improved
technology has cut the cost of desalination in half in the past decade, making
it more competitive. And traditional water supplies, such as the Colorado
River and snow-melt runoff, are becoming less reliable because of population
growth and environmental restrictions.

“We have to get our water from somewhere, and it’s going to be the Pacific
Ocean,” says Gary Arant, manager of the Valley Center Municipal Water
District, which serves farms and homes around San Diego. His district has
agreed to buy almost 15% of the Carlsbad plant’s output. Poseidon says it has
signed 30-year contracts with nine local water districts t
o sell all the
water; about 40% would go to the city of Carlsbad.
To read the rest of this story from the Wall Street Journal, click here. If you
take the link and can’t read the whole article, do this: Go to
http://news.google.com/, type in “California desalination” in the search bar,
and it will give you the whole article. I don’t think you have to be registered
with google to do this, but I am not sure. The article is lengthy and detailed
as you would expect from the WSJ, worth the extra trouble to read it if this is
a topic that interests you.

Meanwhile, work continues on developing a solar powered desalination system.
From the Sydney Morning Herald:

The engineer and his team at the Fraunhofer Institute for Solar Energy Systems
(ISE) have developed small decentralised units with their own solar power
supplies that can transform salt water or brackish water into pure drinking
water. “Our plants work on the principle of membrane distillation,” says
Koschikowski, comparing the technology to that used in breathable, waterproof
fabrics, where the membrane prevents rainwater from penetrating through to the
skin, while allowing water vapour to pass through to the outside.

“In our plant, the salty water is heated up and guided along a micro-porous,

water-repellent membrane. Cold drinking water flows along the other side of
the membrane,” he says. The steam pressure gradient resulting from the
temperature difference causes part of the salt water to evaporate and pass
through the membrane. “The salt is left behind, and the water vapour condenses
as it cools on the other side. It leaves us with clean, germ-free water,” says
Koschikowski.

The system is designed for areas such as the arid parts of Asia and Africa where
electricity is not available to power desalination plants.

 

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