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 UN-backed study said on Monday.
Desalination plants pump out 142 million cubic metres (5 billion cubic feet) of salty brine every day, 50 per cent more than previous estimates, to produce 95 million cubic metres of fresh water, the study said.
About 55 per cent of the brine is produced in desalination plants processing seawater in Saudi Arabia, the United Arab Emirates and Qatar, according to the study by the UN Universityโs Canadian-based Institute for Water, Environment and Health (UNU-INWEH).
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 per cent salt, often includes toxins such as chlorine and copper used in desalination, it said. By contrast, global sea water is about 3.5 per cent salt.
Waste chemicals โaccumulate in the environment and can have toxic effects in fishโ, said Edward Jones, the lead author at UNU-INWEH who also works at Wageningen University in the Netherlands.
Brine can cut levels of oxygen in seawater near desalination plants with โprofound impactsโ on shellfish, crabs and other creatures on the seabed, leading to โecological effects observable throughout the food chainโ, he said.
Vladimir Smakhtin, director of UNU-INWEH, said the study was part of research into how best to secure fresh water for a rising population without harming the environment.
LAKES, RIVERS
โThere are all sorts of under-appreciated sources of water,โ he said, ranging from fog harvesting to aquifers below the seabed. The study also involved the Gwangju Institute of Science and Technology in South Korea.
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.
Gurpal Toor, a water quality expert at the University of Maryland who was not involved in the study, said brine โcould be a serious issue in a small body of waterโ like an inland lake.
Brine can be used inland for irrigating salt-tolerant crops, for fish farming or to produce table salt, he said.
Alex Drak, an engineer at IDE Technologies in Israel, a leading water treatment firm, said properly processed brine from coastal plants dissolves quickly in the sea.
โWe see a lot of marine life, different types of fish, in the vicinity to the discharge point,โ said Drak, who was not involved in the UNU study.
