Hydrology: A Question of Birthright

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According to Aristotle. Desalinization, one of the oldest methods of all, is getting a workout, not only in Israel but around the world. Aristotle taught his students that "salt water, when it turns into vapor, becomes sweet, and the vapor does not form salt water again when it condenses." Julius Caesar relied on stills to convert salt water for his legions to drink during the siege of Alexandria. Ancient mariners learned to boil their drinking water from the sea. Only now, however, is desalinization being attempted on a large scale.

The techniques are as varied as the scientific imagination. Distillation by the heat of the sun seems satisfactory on the Greek island of Syme, but it requires too much space and sunshine to be practical almost anywhere else. Though not economical for seawater conversion, electrodialysis, in which electrically charged cellulose-acetate membranes attract the impurities, is being used to convert less salty but brackish waters. Still another method involves freezing. As a youth in Siberia, Alexander Zarchin, an Israeli engineer, became fascinated by the fact that he could drink melted water from the ice of salty seas. In freezing, he learned, the ice crystals form separately from the brine, then melt down as fresh water. One important advantage of this kind of desalinization is that it takes less power to freeze than to heat. A prototype plant, developed by Zarchin and built by Colt Industries Inc. of the U.S., is now in operation at the Red Sea port of Elath.

Most of the world's 200 desalinization plants, though, from Kuwait to Aruba to Chocolate Bayou, Texas, operate on the "teakettle technique," the colloquial name for multistage flash distillation. In this system, sea water is heated and sprayed into a low-pressure chamber where it flashes into steam. As it passes through a series of similar chambers, even more fresh water is steamed off until, in the more efficient operations, an average of 3½ gallons of sea water is turned into a gallon of fresh. So pure is the result that sometimes a jigger of such contaminants as magnesium salts is tossed back in to eliminate the bland, distilled taste.

Similar systems can be adapted to almost any fuel—electricity, natural gas, or nuclear energy. In teeming Hong Kong, a desalinization plant is powered by burning garbage. It is the more immediate problem of cost that causes the most concern. By improving technology and experimenting with large-scale operation, engineers have already lowered the average cost of desalinization from about $5 per 1,000 gallons of water in 1952 to about $1. But the goal is still far off—less than 35¢, which would make desalinized water competitive in price with natural water in the U.S.

When that distant goal is reached, another difficulty will arise: mountains of coarse, unusable salt will somehow have to be disposed of. Every quart of sea water contains an average of 1¼ oz. of salt; a 150-million-gallon-capacity plant would end up producing more than 23,000 tons of salt a day. "Only when you have effective water management and still have a shortage," says Jack Hunter, an assistant director of the Interior Department's Office of Saline Water, "then desalinization may be the answer."