The water we drinkMajor breakthrough in desalination technology could be game changer

Published 17 January 2011

A new desalination technique could be a significantly cheaper and more energy efficient alternative to aqueducts and dams; Oasys Water has developed ground breaking new membranes and draw solutions that generate fresh water faster, more efficiently, and at lower temperatures than existing desalination methods

Boston, Massachusetts-based Oasys Water has developed a groundbreaking new desalination technology that could dramatically change where communities draw their water from.

As MIT Technology Review reports, the company’s technology can produce drinking water in a process that is significantly faster, cheaper, and more energy efficient than most existing methods.

According to Robert McGinnis, Oasys Water cofounder and inventor of the core technology, “the cost will be low enough to make aqueduct and dam projects look expensive in comparison.” He added, “the fuel consumption and carbon emissions will be lower than those of almost any other water source besides a local lake or aquifer.”

Existing desalination methods are energy intensive, expensive, and slow. Salt water is either heated until it evaporates and the vapors are then captured and cooled or the water is passed through a membrane that separates the salt from the water.

Oasys Water combines the two existing techniques of passing water through a membrane and then heating the mixture. Oasys technology is unique in that it has made this process more efficient by designing a draw solution with easy to remove solutes as well as a reengineered membrane that allows water to pass through twenty five times faster.

A thin membrane separates sea water from the draw solution which contains carbon dioxide and ammonia. The water naturally moves to the concentrated solution, while the membrane blocks the salt and other impurities from passing through. The mixture is then heated to evaporate carbon dioxide and ammonia leaving fresh water behind. The ammonia and carbon dioxide are captured and reused.

The solution only has to be heated to forty to fifty degrees Celsius compared to other processes that require water to be heated to seventy to 100 degrees Celsius, resulting in cost savings.

Others have tried to develop other solutes for desalination,” McGinnis says, “but they haven’t been successful so far.”

To maximize energy efficiency, this new technique can use waste heat from power plants – that would simply be released into the atmosphere – to evaporate the solution. Most desalination plants are already located in power plants, but they require additional fuel and energy to heat salt water.

The Oasys Waters’s technique is cheaper than existing membrane based desalination plants as it requires only one-tenth the energy and cheaper equipment.

Current membrane based techniques force water through a membrane at high pressure which requires a significant amount of electricity. Not pressurizing the water would result in cost savings as electricity accounts for nearly half of the expenses in this process. Further cost savings are realized as expensive pipes designed to withstand high pressure do not have to be installed.

Desalination, once a very expensive option used only in regions with limited alternatives, could now be a realistic option for communities that have to transport fresh water over long distances. For instance, in California a massive aqueduct carries water from Northern California to Southern California.

As cities located far away from fresh water sources continue to grow, the need for desalination plants will only become greater. According to Kenneth Herd, director of the water supply program at the Southwest Florida Water Management District, cities will increasingly turn to desalination.

It’s not a matter of if,” Herd says, “but a matter of when.”

Oasys Water is currently testing the complete system and pans to start selling it by the end of 2011.