A look at the desalination process

May 5, 2008 10:32:25 AM PDT
The rise in desalination plans in California -- and whether they create more problems than they solve.

In the next 40 years, California's population is expected to grow by 25 million people. Will there be enough water to meet the demand?

Agencies up and down the state are looking for alternative sources, and the Pacific Ocean may turn out to be one of the answers if we are willing to pay the price.

It is essential to life as we know it, clean drinkable water. But with rivers and streams already taxed and marine life struggling, water officials are searching for new sources of fresh water.

And they're hoping to find it in the salty ocean.

"This is where the water is separated from the salt or the salt is separated from the water," said Jim Heitzman from the Marina Coast Water District.

Heitzman is general manager of the Marina Coast Water District near Monterey. The agency has been sucking water from the ocean and making it drinkable since 1997.

The small plant can provide water for nearly a thousand homes. It is one of several around the state that is being used to study the feasibility of desalination plants.

"For the past 10 years it's been pretty successful. It's given a lot of data and put a lot of information out there and hopefully it will lead to a bigger plant," said Heitzman.

The water district is now hoping to build that bigger plant near a garbage dump, using the methane gas expelled by the site to power the water plant. That plant could potentially provide enough water for 10,000 homes each year.

Lyndel Melton is with the company that's planning the project.

"We know of no other system exactly like this, but we know that each of these components has been used someplace else and we have a lot of experience and confidence in their use," said Melton.

The State Department of Water Resources says desalination plants are being tested or proposed all over the state. They won't solve the problem, but might make a dent.

"It is expected that desalination would play not major role, maybe less than 10 percent," said Fehti Ben Jamaa from the California Department of Water Resources.

A plant in Santa Cruz plant opened in March to create a back-up water supply in case there's a drought.

"It's proving to be viable all over the world and now in the United States," said Brent Haddad from the Center for Integrated Water Research at UC Santa Cruz.

Haddad says we need more desalination plants.

"We need more water. It's very stressful to society and to the economy and its energy intensive to move water over long distances," said Haddad.

But not everybody thinks desalination makes the most sense.

"It's not without its risks, it's not without its costs," said Peter Gleick from the Pacific Institute.

Gleick is co-author of a report for the non-profit Pacific Institute.

The report found the amount of energy needed to run desalination plants makes them cost prohibitive. They cost consumers 50 to 100 percent more than regular sources of water.

"Economically desalination is very expensive, far more expensive than many of the alternatives we have available to us in California. Conservation and efficiency, transfers for agriculture. It's an expensive source of water," said Gleick.

And then there are environmental concerns.

"We're not opposed to desalination per se, we're concerned about doing it right," said Peter Douglas from the California Coastal Commission.

The California Coastal Commission worries that turning ocean water into fresh water would bring more people to California's already fragile coast.

They also worry about the impact a desalination plant may have on wildlife.

"What are the impacts, for example, if you use a technology that draws in ocean water and you draw in marine life. So all marine life that's sucked into these facilities or these plants dies," said Douglas.

Dumping all that salt back into the ocean may also create dead zones.

That kind of concern has led several Bay Area water agencies to plan a desalination plant at the mouth of the delta, instead of on the coast. A test plant will be built this summer at a site near Pittsburg.

"It's basically to take water out of the delta, treat it, and then put it into the large transmission system of two of the entities, Contra Costa and East Bay MUD. but that would allow us to get water from there to San Francisco residents and customers and Santa Clara Valley Water District customers," said Michael Carlin from SF Public Utilities Commission.

The water in the delta is not as salty as ocean water, so it will require less energy to filter out the salt and be cheaper. But no matter where you put a desalination plant, it's still more expensive than traditional water sources.

Whether people will be willing to pay the price ultimately depends on how desperate we get.

"If there is climate change and there's a long term drought, you still have a ready water supply," said Heitzman.

Advances in desalination over the last 30 years have made it increasingly attractive.

It may never be our main source, more than half of the fresh water in the Middle East and Northern Africa is supplied by desalination plants.

Written and produced by Ken Miguel.


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