For Drinking Water in Drought, California Looks Warily to Sea

CARLSBAD, Calif. — Every time drought strikes California, the people of this state cannot help noticing the substantial reservoir of untapped water lapping at their shores — 187 quintillion gallons of it, more or less, shimmering so invitingly in the sun.

Now, for the first time, a major California metropolis is on the verge of turning the Pacific Ocean into an everyday source of drinking water. A $1 billion desalination plant to supply booming San Diego County is under construction here and due to open as early as November, providing a major test of whether California cities will be able to resort to the ocean to solve their water woes.

Across the Sun Belt, a technology once dismissed as too expensive and harmful to the environment is getting a second look. Texas, facing persistent dry conditions and a population influx, may build several ocean desalination plants. Florida has one operating already and may be forced to build others as a rising sea invades the state’s freshwater supplies.

In California, small ocean desalination plants are up and running in a handful of towns. Plans are far along for a large plant in Huntington Beach that would supply water to populous Orange County. A mothballed plant in Santa Barbara may soon be reactivated. And more than a dozen communities along the California coast are studying the issue.

The technological approach being employed here, and in most recent plants, is called reverse osmosis. It involves forcing seawater through a membrane with holes so tiny that the water molecules can pass through but larger salt molecules cannot.

A huge amount of energy is required to create enough pressure to shove the water through the membranes. But clever engineering has cut energy use of the plants in half in 20 years, as well as improving their reliability.

Future desalination plants also have the potential to blend well with the rising percentage of renewable power on the electric grids in California and Texas. Since treated water can be stored, the plants could be dialed up at times when electricity from wind or solar power is plentiful, and later dialed down.

Full article: For Drinking Water in Drought, California Looks Warily to Sea (NY Times)

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