Converting the oceans into drinking water could be environmentally costly

Converting the oceans into drinking water could be environmentally costly

By Luke Vargas   
Published
The global distribution of large desalination plants by capacity, feedwater type and desalination technology. Courtesy: United Nations University - Institute on Water, Environment and Health.
The global distribution of large desalination plants by capacity, feedwater type and desalination technology. Courtesy: United Nations University - Institute on Water, Environment and Health.

The world's 16,000 desalination plants are producing high amounts of brine that threaten to deplete certain underwater environments of oxygen.

UNITED NATIONS – Desalination, the process through which salt water is converted into usable freshwater, is rapidly rising to address the challenge of global water shortages and has already rendered chronically-dry corners of the world habitable.

There are nearly 16,000 desalination plants around the world, with the highest concentration in the Middle East and North Africa. Those plants often treat seawater and tend to be larger and less efficient than those in North America that mostly treat rivers and estuaries.

And new research published this week suggests that super salty brine discharged at desalination plants bordering the world’s oceans is causing problems of its own.

“The salinity is potentially a big problem, especially in not very well-flushed areas.”

Edward Jones is an environmental scientist and researcher at Wageningen University in the Netherlands.

“If we’re dumping lots of brine into the ocean whereby there’s not much circulation, this can cause saline underflows within the ocean. And basically, this can reduce the dissolved oxygen content and this is the reason why there can be associated risks for the ecology – organisms that live on the seafloor can suffer from this lack of oxygen in conditions we call hypoxia.”

By one estimate, desalination plants produce 1.5 liters of brine for every liter freshwater they produce. And with an estimated 95 million cubic meters of desalinated water now produced each day, that’s a lot of brine.

Worse still, are plants that use toxic chemicals like chloride and copper in the desalination process.

“These are the toxic elements that can potentially accumulate in the environment and cause negative effects for marine life.”

There are some possible fixes on the horizon. By mixing brine with “wastewater” or “power-plant cooling water,” the resulting discharge can be less salty and less harmful to the environment. Brine can also be converted into lye and various industrial gasses.

But until those processes become less expensive, the variant of an old adage will remain true: There’s no such thing as a free drink.

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