FRESH WATER FROM THE SEA

Press, Volume C, Issue 29620, 16 September 1961, Page 8

FRESH WATER FROM THE SEA

Future Sources Depend On Research t Written by ROBERT STEVENS for the United States Information Service)

FREEPORT (Texas). WATER is an almost unlimited natural resource. But most of it has remained untapped, for the preponderance of the earth’s water is in the sea—saltv, undrinkable, useless for agriculture and industry.

Fresh-water sources are relatively scant and inequitably distributed among nations. Because of nature’s capriciousness, some countries have been forced to devote much of their energies to meet the drinking-water needs of their people. Progress for them has been slow and difficult. Development of agriculture and industry, with their enormous thirts for fresh water, has been almost out of the question in these “dry” countries of the world.

Abundant supplies of natural fresh water have made possible highly developed technology, agriculture, and living standards in the United States and other nations. With ever-increasing populations, food requirements, and industrialisation, however, the water-rich nations are becoming less and less amply endowed.

Conservationists and scientists have become sharply aware of impending water shortages in the United States. Some of them have estimated that the problem will become severe within ten years. Thus, during the last two or three years, a growing research and development effort has been under way toward economical conversion of salt water to fresh. The first concrete success to come out of this recent effort—which is to a considerable extent sponsored by the United States Office of Saline Water —is the new demonstration plant dedicated here in Freeport on June 21. A peculiar-looking maze of plumbing, the plant draws its supply from the salty Gulf of Mexico and produces clear, sparkling water for the people of the small city. It turns out more than 1,000,000 gallons a day at a cost of about one dollar per 1,000 gallons. This is slightly more than half the water cost from the world’s next most efficient major plant. The Freeport unit bodes well for future progress through scientific and technological research. It also recalls cehturies of previous thought and experimentation toward economical conversion of sea water.

Man’s quest for ways to freshen salt water goes back more than 2000 years, As early as 350 8.C., Aristotle recorded some Greek experiments toward that end. The Roman legions of Julius Caesar utilised primitive solar stills for their drinking water at Alexandria in 49 B.C. Sir Francis Bacon discussed the problem in detail in 1567, for his Queen Elizabeth I, Fad offered a handsome reward to the inventor , of a sea-water conversion machine which would allbw the sailors of the English Navy to stay at sea for longer periods. In 1791, Thomas Jefferson, before he became President of the United States, reported to Congress after witnessing a demonstration of a process developed by a Mr Jacob Isaacks. “Mr Isaacks,” Jefferson wrote, “fixed the pot of a small caboose with a tin cap and a straight tube of tin passing obliquely through a cask of cold water. He made use of a mixture, the com-

position of which he did not explain, and by heating 24 pints of sea water ... he distilled 22 pints of fresh water in four hours . . ,

Jefferson, an intellectually curious man, undertook his own experiment, duplicating Isaacks, except for the “secret mixture.” He produced 31 pints of clear water from 32 pints taken out of the sea. Though the technique was npt especially economical, it did mark the beginning of America's interest in saltwater conversion to fresh water.

World-wide research (stepped up enormously in the last few years) led to the development of the Freeport plant, which, in fact, is based on a well, known “long-tube-vertical, multilpe-effect distillation process” employed in the chemical industry. The same holds fpr four additional demonstration plants soon to be constructed for the Office of Saline Water and for the 17 or so major conversion plants now in operation around the world. Dramatically different techniques will depend on basic research into the nature of salt water, about which surprisingly little is known. Technologists, meanwhile, are continuing to apply existing knowledge in the development of better saltwater conversion methods. Here is a sampling of systems from some technological research laboratories: The General Electric Company has developed a “wiped film" technique of distillation. The machine consists essentially of two tubes, one inside the other, and a set of blades similar to those of an automobile windshield wiper. The blades extend the length of the inner tube.

Sea water is pumped through narrow outlets at the edges of the blades, which rotate round the interior wall of the inner tube, thus spreading the water in a thin film. The wall is heated by steam confined in the space between the two tubes, vapour given off by the now hot film of sea-water is directed into a -cooler where it condenses into fresh water.

A freezing technique is being utilised by the Fair-banks-Whitney Corporation in the manufacture of a series of plants which will produce fresh water at the edge of 'the Negev Desert for the Israeli nation, Credit for the technique goes to an Israeli scientist, Alexander Zarchin, who left his home land, Soviet Russia, in 1947. The central idea for the project is an old one —-"the fact that when sea water freezes the resultant ice is free of salt. In operation, cooled sea water is sprayed

into a vacuum tank. Some of it evaporates and is sucked into a condenser where it becomes fresh water. Part of the sprayed water is frozen by the cooling effect of the evaporation. It drops to the bottom of the tank and mixes with the remaining brine. The two are separated by screening, and the ice is melted.

Another freezing process, under, tests by the BlawKnox Company, involves a salt-water and butane mixture. Since butane boils at a temperature just below the freezing point of sea water, it is used in both its liquid and gaseous forms to freeze the water and melt the ice. Because of the closeness of the critical temperature points, little additional energy is needed to keep the process going. Syracuse University is studying a method of separating water from salt by addition of chemicals. The product of the reaction is a solid which takes up water, but not salt, into its crystalline structure. The solid is melted to remove the water, and the chemical is re-used in the process. Among the many other possible techniques for sea-water purification is that of biological removal of salt. Experiments at the University of California, Los Angeles, have shown that algae (microscopic one-celled plants) ingest the salt, considerably reducing its concentration in sea water. One advantage of this process, should it prove workable, is that little or no outside energy (for heat, refrigeration, etc.) would be needed. What scientists and technologists are striving for in these efforts is not simply ways to change salt water into fresh water, but, rather, ways to do it at the smallest possible expense. They are working long and hard, and each success, small as it may be, is a step toward progress for all nations in drawing vital fresh water from the unlimited resource of the sea.