The Dirty Truth About Turning Seawater Into Drinking Water

As countries in the Middle East, Africa, and elsewhere struggle to find enough freshwater to meet demand, they’re increasingly turned to the ocean. Desalination plants, located in 177 countries, can help turn seawater into freshwater. Unfortunately, these plants also produce a lot of waste—more waste, in fact, than water for people to drink.

paper published Monday by United Nations University’s Institute for Water, Environment, and Health in the journal Science of the Total Environment found that desalination plants globally produce enough brine—a salty, chemical-laden byproduct—in a year to cover all of Florida in nearly a foot of it. That’s a lot of brine.

In fact, the study concluded that for every liter of freshwater a plant produces, 0.4 gallons (1.5 liters) of brine are produced on average. For all the 15,906 plants around the world, that means 37.5 billion gallons (142 billion liters) of this salty-ass junk every day. Brine production in just four Middle Eastern countries—Saudi Arabia, Kuwait, Qatar, and the United Arab Emirates—accounts for more than half of this.

The study authors, who hail from Canada, the Netherlands, and South Korea, aren’t saying desalination plants are evil. They’re raising the alarm that this level of waste requires a plan. This untreated salt water can’t just hang around in ponds—or, in worst-case scenarios, go into oceans or sewers. Disposal depends on geography, but typically the waste does go into oceans or sewers, if not injected into wells or kept in evaporation ponds. The high concentrations of salt, as well as chemicals like copper and chlorine, can make it toxic to marine life.

“Brine underflows deplete dissolved oxygen in the receiving waters,” said lead author Edward Jones, who worked at the institute and is now at Wageningen University in the Netherlands, in a press release. “High salinity and reduced dissolved oxygen levels can have profound impacts on benthic organisms, which can translate into ecological effects observable throughout the food chain.”

Instead of carelessly dumping this byproduct, the authors suggest recycling to generate new economic value. Some crop species tolerate saltwater, so why not use it to irrigate them? Or how about generating electricity with hydropower? Or why not recover the minerals (salt, chlorine, calcium) to reuse elsewhere? At the very least, we should be treating the brine so it’s safe to discharge into the ocean.

Countries that rely heavily on desalination have to be leaders in this space if they don’t want to erode their resources further. And this problem must be solved before our dependency on desalination grows.

The technology is becoming more affordable, as it should, so lower-income countries that need water may be able to hop on the wave soon. While this brine is a problem now, it doesn’t have to be by then.

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