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Desalination plants creating salty dilemma, globally: UN

IANS  |  New Delhi 

The fast-rising number of plants worldwide -- now almost 16,000, with capacity concentrated in the and -- quench a growing thirst for freshwater but create a salty dilemma as well - how to deal with all the chemical-laden leftover

In a UN-backed study made public on Monday, experts estimate the freshwater output capacity of plants at 95 million cubic meters per day -- comparable to 40 per cent of the high season flow over

For every litre of freshwater output, however, plants produce on average 1.5 litres of (though values vary dramatically, depending on the feedwater salinity and used and local conditions).

Globally, plants now discharge 142 million cubic meters of hypersaline every day, a 50 per cent increase on previous assessments.

That's enough in a year (51.8 billion cubic meters) to cover under 30.5 cm (one foot) of brine.

The authors, from UN University's Canadian-based Institute for Water, and Health, in The and the and Technology in Korea analysed a newly-updated dataset -- the most complete ever compiled -- to revise the world's badly outdated statistics on desalination plants.

And they call for improved brine management strategies to meet a fast-growing challenge, noting predictions of a dramatic rise in the number of desalination plants, and hence the volume of brine produced, worldwide.

Eight countries -- the Maldives, Singapore, Qatar, Malta, Antigua and Barbuda, Kuwait, The and -- can meet all of their needs through desalination.

Six others can meet over 50 per cent of their withdrawals through desalination: Equatorial Guinea, UAE, Seychelles, Cape Verde, and

The paper found that 55 per cent of global brine is produced in just four countries: (22 per cent), UAE (20.2 per cent), (6.6 per cent) and (5.8 per cent).

Middle Eastern plants, which largely operate using seawater and thermal desalination technologies, typically produce four times as much brine per cubic meter of clean as plants where river water membrane processes dominate, such as in the US.

The paper says brine disposal methods are largely dictated by geography but traditionally include direct discharge into oceans, surface water or sewers, deep well injection and brine evaporation ponds.

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

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 used as anti-scalants and anti-foulants in the desalination process. Copper and chlorine are of major concern.

"Brine underflows deplete dissolved oxygen in the receiving waters," says Edward Jones, who worked at UNU-INWEH and is now at Wageningen University, The

"High salinity and reduced dissolved oxygen levels can have profound impacts on benthic organisms, which can translate into ecological effects observable throughout the "

The paper also highlights economic opportunities to use brine in aquaculture, to irrigate salt tolerant species, to generate electricity, and by recovering the salt and metals contained in brine -- including magnesium and gypsum.

With better technology, a large number of metals and salts in desalination plant effluent could be mined.

These include sodium, magnesium, calcium, potassium, bromine, boron, strontium, lithium, rubidium and uranium, all used by industry, in products, and in agriculture.



(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)

First Published: Mon, January 14 2019. 20:46 IST