Almost 16,000 desalination plants worldwide produce bigger-than-expected flows of highly salty waste water and toxic chemicals that are damaging the environment, a U.N.-backed study said.
Desalination plants pump out 142 million cubic meters (5 billion cubic feet) of salty brine every day, 50 percent more than previous estimates, to produce 95 million cubic meters of fresh water, the study said.
About 55 percent of the brine is produced in desalination plants processing seawater in Saudi Arabia, the United Arab Emirates and Qatar.
The hyper-salty water is mostly pumped into the sea and, over a year, would be enough to cover the U.S. state of Florida with 30 cms (one foot) of brine, it said of the fast-growing and energy-intensive technology that benefits many arid regions.
Brine, water comprising about five percent salt, often includes toxins such as chlorine and copper used in desalination, it said. By contrast, global sea water is about 3.5 percent salt.
Brine can cut levels of oxygen in seawater near desalination plants with “profound impacts” on shellfish, crabs and other creatures on the seabed, leading to ecological effects observable throughout the food chain. Brine from desalination plants that tap brackish lakes, aquifers or rivers far inland is harder to treat than brine from coastal plants that can be piped into the seas.
As a solution to the problem, brine can be used inland for irrigating salt-tolerant crops, for fish farming or to produce table salt. Also, properly processed brine from coastal plants dissolves quickly in the sea and does not have harmful effects on marine life.