Older, thermal plants, which used heat to turn salt water into steam, delivered potable water at more than $3 per cubic metre.

reverse osmosis technology — in which water is pushed through a membrane to remove salt, minerals and impurities — has taken over

Plants cost less to build — perhaps $400mn to purify 500,000 cubic metres per day, says Christopher Gasson of GWI. Including installation, a return on capital and operating costs, that translates to $0.30 per cubic metre of water

Newer plants also need less energy — 2.6KWh per cubic metre — and are increasingly powered by cheap solar plants

cheapest plant in the world gets energy at $0.025/KWh, or $0.07 per cubic metre

Hassyan project in Dubai has promised desalinated water at just $0.37 per cubic metre

drinking water in London is priced at £1 per cubic metre

Desalination has also become cheaper than building new infrastructure to transport water over long distances



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