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Another Voice: Reverse osmosis may help sea water solve critical fresh water shortages

By Frank Dinan

“Water, water, everywhere, nor any drop to drink.”

Is there a better motto for California than this line from Samuel Taylor Coleridge’s epic poem? Many other regions of the world may also wish to consider this motto as drinkable water becomes scarcer. According to the United Nations, more than 1 billion people now live in regions where drinking water is scarce, and that figure is expected to reach 1.8 billion by 2025.

While our oceans contain inexhaustible amounts of water, more than 97 percent of it is too salty to drink. Of our less than 3 percent of fresh water, much of it is inaccessible to us, so it is no surprise that population growth, prolonged droughts and excessive water use have combined to force populous yet arid areas such as California to restrict water use. However, other arid regions such as Saudi Arabia, Australia and Israel are currently obtaining drinking water using a technology called reverse osmosis (RO) that has grown rapidly in recent times.

Osmosis occurs in all plants and animals. It maintains all life on Earth by causing water to flow from ground level into the top branches of the tallest trees and across cell wall membranes in all plants and animals.

Reverse osmosis, however, is the opposite of osmosis. In desalinization by RO, pressure is applied to salty ocean water to force water to flow across a porous membrane that has holes that are too small for the salt to cross, converting ocean water into drinkable water.

Water produced by RO is expensive relative to fresh water. RO plants must be built, power supplied to them and membranes maintained. However, two trends are occurring that are narrowing the price gap. Fresh water supplies are decreasing constantly, making drinkable water increasingly scarce and expensive, while technological improvements are increasing RO’s efficiency. These trends will continue.

RO plants now exist in Florida, Texas, Arizona and California and their numbers and capacities are growing. The largest RO desalinization plant is currently under construction near San Diego, and many more will soon be under way. They had better be, because the United States ranks third in fresh water use behind two far more populous countries, China and India. We use more than twice as much fresh water per capita as Great Britain and nearly triple that of China and India. This is not sustainable.

RO technology has drawbacks other than cost, but they are being overcome and they must be if the world is to have adequate drinking water. Californians are learning that fresh water is not inexhaustible. Our futures and, perhaps, the world’s may depend on all of us learning this hard lesson.

Frank Dinan is an emeritus professor in the Chemistry and Biochemistry Department at Canisius College.