Chapter 15: Restless Realm: Oceans and Coasts
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Can We Drink the Ocean?
by Stephen Marshak
Marine Evaporite deposit
"Water, water, everywhere, /Nor any drop to drink"—Samuel Taylor Coleridge's famous lament (in The Rime of the Ancient Mariner), echoed by many a castaway languishing on a raft, holds true on a global basis too. With so much ocean water around, why do we constantly hear of water shortages? Simply because we can't drink seawater or use it for industrial or agricultural purposes. Seawater, as we have seen, contains about 3.5% salt, while drinking water cannot contain more than 0.05%. We can, however, extract drinking water from seawater by distilling it. A distillation plant, or desalinizationplant, consists simply of a furnace that boils seawater. Only freshwater goes into the steam, leaving the salt behind; the plant then transforms the steam back into water by cooling it in a coil of glass tubing. But while the method is simple the cost is high, for it takes a lot of energy to boil water. As a result, the water obtained from a desalinization plant costs about ten times more than fresh-water pumped out of the ground. Consumers can justify the cost of distilled drinking water only in places like the Netherelands Antilles, a group of desert islands north of Venezuela, which completely lack natural freshwater supplies and cannot receive water by pipeline. Because of the cost of desalinization, some Middle Eastern nations have considered towing huge icebergs from Antarctica up to the Persian Gulf, since water leaves salt behind when it freezes. But most of the glacier would melt before it even reached its destination, and the cost of towing it would be prohibitive.
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