SOURCE: United Nations University

DATE: January 14, 2019

SNIP: The fast-rising number of desalination plants worldwide — now almost 16,000, with capacity concentrated in the Middle East and North Africa — quench a growing thirst for freshwater but create a salty dilemma as well: how to deal with all the chemical-laden leftover brine.

In a UN-backed paper (“The state of desalination and brine production: A global outlook“), experts estimate the freshwater output capacity of desalination plants at 95 million cubic meters per day — equal to almost half the average flow over Niagara Falls.

For every litre of freshwater output, however, desalination plants produce on average 1.5 litres of brine (though values vary dramatically, depending on the feedwater salinity and desalination technology used, and local conditions). Globally, plants now discharge 142 million cubic meters of hypersaline brine every day (a 50% increase on previous assessments).

Desalination plants near the ocean (almost 80% of brine is produced within 10km of a coastline) most often discharge untreated waste brine directly back into the marine environment.

The authors cite major risks to ocean life and marine ecosystems posed by brine greatly raising the salinity of the receiving seawater, and by polluting the oceans with toxic chemicals used as anti-scalants and anti-foulants in the desalination process (copper and chlorine are of major concern).