Clean water with less energy

Posted by Laura Grant on February 4, 2009
Posted in Green News

water drop
Photograph by Snap, licensed under Creative Commons licence.

Given the state of the water supply in South Africa (which has been described as a looming crisis) and our electricity shortage, a new water desalination and purification technology that uses significantly less energy to harvest drinkable water from nonpotable sources – sea water and waste water, for instance – sounds like something worth keeping an eye on.

Developed by researchers at Yale in the United States, the system uses “a new twist on an old technology” called forward osmosis. Water naturally flows from a dilute region to one that’s more concentrated when the two solutions are separated by a semipermeable material. The new system “draws” pure water from its contaminants through the membrane to a solution of concentrated salts. This solution has been specially designed to be easy to remove with low heat treatment, which means using less energy.

A company called Oasys has been established to commercialise the technology.

Details of Oasys’s draw solution are apparently a company secret, but it uses ammonia and carbon-dioxide gases dissolved in water in specific proportions, says a report on a Yale website. The solution then can be removed efficiently and reused.

The researchers say their system uses ten times less electrical energy than traditional desalination plants.

A pilot-scale plant to test the technology is producing one cubic meter of water per day, but Oasys aims to raise venture financing to increase output to 1,000 to 10,000 cubic metres of water a day.

The technology has a way to go before it reaches commercial scale, but it may hold hope for affordable water purification in developing countries.

Sources: Ecogeek; Yale; Yale School of Engineering and Applied Science; Water and Waste Treatment

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