Quenching The World’s Thirst Using Seawater Poses Serious Risks As Desalination Dumps Toxic Brine Into Oceans

Source: Scientific American/Erica Gies 

Photo: Rawpixel/Unsplash

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Growing populations and tightening water supplies have spurred people in many places—including the Middle East, Australia, California and China—to look to the oceans and other salty waters as a source of new drinking water. But desalination plants are energy intensive and create a potentially environment-harming waste called brine (made up of concentrated salt and chemical residues), which is dumped into the ocean, injected underground or spread on land.

Despite the ecological threats, “there was no comprehensive assessment about brine—how much we produce,” says Manzoor Qadir, assistant director of the United Nations University Institute on Water, Environment and Health. So he and his colleagues calculated that figure and found it is 50 percent greater than the desalination industry’s previous rough estimate. In fact, it is enough to cover Florida with 30 centimeters of brine every year.

How much brine a desalination plant produces depends on its water source—such as seawater or brackish (semisalty) water—and on the type of technology it employs, Qadir says. Reverse osmosis, which pushes water through a membrane to strain out the salt, is the most widely used technology today and produces 69 percent of the world’s desalinated water.

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