Plans to alleviate water shortages by making sea water drinkable have been abandoned as too expensive.
South East Water, which supplies 1.5 million homes in the region, explored the possibility of desalinating water by installing a pilot plant at Newhaven in East Sussex.
The water company was one of many in the south-east to impose a hosepipe ban during the drought last summer.
Tests were carried out over an 18-month period to test how effective it could be to turn sea water into drinking water on a large scale.
But the water company has concluded that the high cost and the environmental impact of desalination is unfeasible.
The trial plant tested a two-stage treatment process. First, the water was filtered through sand to remove solid particles and bacteria from the water.
In the second stage the water was forced through a super-fine membrane at high pressure which dissolved salts and other pollutants and produced pure, clean water.
South East Water calculated the cost of producing one million litres of desalinated water during water shortages or peak demand was nearly 10 times higher compared to the cost of extracting and treating river water.
It would cost £450 to produce one million litres of sea water compared to £50 for the same amount of river water and £35 for ground water.
The company also considered using solar power to run a desalination plant capable of producing 9.5 million litres of drinking water a day.
It concluded that solar panels one-and-half-times the size of an international football pitch would be needed to produce one million litres of water per day.
And it said there were also ‘significant environmental issues’ associated with the disposal of concentrated saltwater, which is the by-product of the desalination process.
David Shore, operations director at South East Water, said: ‘Our trial has demonstrated that desalination is not yet the right solution for delivering extra water at peak times, or during extended dry periods such as droughts.
‘Desalination remains an expensive option in terms of operating and environmental costs.’
He said technological advances have been made in desalination, so it would remain an option for the future.
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