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Can Ocean Desalination Solve the World's Water Shortage?

Environmentalists concerned about long-term effects of desalination

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Dear EarthTalk: Is removing the salt from ocean water (desalination) a feasible fix for the world’s shortage of fresh water?
-- Nora Jones, Sydney, New South Wales, Australia

Fresh water scarcity is already posing major problems for more than a billion people around the world, mostly in arid developing countries. The World Health Organization predicts that by mid-century, four billion of us—nearly two-thirds of the world’s present population—will face severe fresh water shortages.

Population Growth Drives Quest for Water by Desalination
With human population expected to balloon another 50 percent by 2050, resource managers are increasingly looking to alternative scenarios for quenching the world's growing thirst. Desalination—a process whereby highly pressurized ocean water is pushed through tiny membrane filters and distilled into drinking water—is being held forth by some as one of the most promising solutions to the problem. But critics point out it doesn't come without its economic and environmental costs.

Costs and Environmental Impact of Desalination
According to the non-profit Food & Water Watch, desalinated ocean water is the most expensive form of fresh water out there, given the infrastructure costs of collecting, distilling and distributing it. The group reports that, in the U.S., desalinated water costs at least five times as much to harvest as other sources of fresh water. Similar high costs are a big hurdle to desalination efforts in poor countries as well, where limited funds are already stretched too thin.

On the environmental front, widespread desalination could take a heavy toll on ocean biodiversity. "Ocean water is filled with living creatures, and most of them are lost in the process of desalination," says Sylvia Earle, one of the world's foremost marine biologists and a National Geographic Explorer-in-Residence. “Most are microbial, but intake pipes to desalination plants also take up the larvae of a cross section of life in the sea, as well as some fairly large organisms…part of the hidden cost of doing business,” she says.

Earle also points out that the very salty residue left over from desalination must be disposed of properly, not just dumped back into the sea. Food & Water Watch concurs, warning that coastal areas already battered by urban and agricultural run-off can ill afford to absorb tons of concentrated saltwater sludge.

Is Desalination the Best Option?
Food & Water Watch advocates instead for better fresh water management practices. "Ocean desalination hides the growing water supply problem instead of focusing on water management and lowering water usage," the group reports, citing a recent study which found that California can meet its water needs for the next 30 years by implementing cost-effective urban water conservation. Desalination is "an expensive, speculative supply option that will drain resources away from more practical solutions," the group says.

Despite such arguments, the practice is becoming more common. Ted Levin of the Natural Resources Defense Council says that more than 12,000 desalination plants already supply fresh water in 120 nations, mostly in the Middle East and Caribbean. And analysts expect the worldwide market for desalinated water to grow significantly over the coming decades. Environmental advocates may just have to settle for pushing to "green" the practice as much as possible in lieu of eliminating it altogether.

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EarthTalk is a regular feature of E/The Environmental Magazine. Selected EarthTalk columns are reprinted on About Environmental Issues by permission of the editors of E.

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