Desalination getting serious.

In discussions of the growing global water crisis, the option of desalination--making fresh water" out of sea water--has rarely been taken seriously because the cost, at least for large volume uses, has been prohibitive. Only in a few arid but oil-rich countries of the Middle East and North Africa has it seemed to make sense to expend the energy needed to remove salt on a large scale. Saudi Arabia has 27 desalination plants producing about 12 million cubic meters of fresh water per day and providing 70 percent of the nation's drinking water. The UAR produces about 5.5 million cubic meters, and Kuwait about 3 million.

But now, even in the United State where water is relatively inexpensive, desalination is gaining a place in the supply picture, at least in a few locations. In Tampa, Florida, a new $100 million plant--the largest desalination plant in the Western Hemisphere--opened in May 2003 with an initial output of 25 million gallons per day. The plant is expected to produce about 10 percent of the Tampa Bay region's overall water supply by 2008.

Several factors have combined to make desalination a more viable option now. Global population is continuing to rise, while the planet's natural supply of water is fixed. Per capita consumption is also continuing to rise, as less-developed countries become more industrialized and more water is used for farm irrigation, factory processing, dish-washers, and showers. Meanwhile, the share of the planet's fresh water that can be actually used to meet these demands is declining, as more groundwater becomes contaminated. And in many places, privatization of water markets has created new incentives for pursuing the potentially lucrative business of turning salt water to fresh.

At the same time, new technology has brought the cost of desalination down. A new "spray-flash" technique developed at Saga University in Kyushu Japan, makes efficient use of differences in ocean temperatures by generating vapor from warm surface water, then cooling it with deep ocean water and condensing it to make fresh water.

At least one aspect of the new surge in desalination could raise a new concern for environmentalists. Many of the desalination plants are built in conjunction with power plants, and in Japan they are being built in conjunction with nuclear power plants, which require water for cooling. With both energy and water supplies becoming increasingly scarce, it isn't hard to imagine a political scenario in which the efficiencies gained by combining nuclear and desalination plants makes the need for fresh water become an argument for giving more longevity to the nuclear option.