Here’s a report from MIT Technology Review (Kevin Bullis):
Oasys Water, a company that has been developing a novel, inexpensive desalination technology, showed off a new development facility in Boston this week. The company, which has been demonstrating commercial-scale components of its system in recent months, plans to begin testing a complete system early next year and to start selling the systems by the end of 2011.
Currently, desalination is done mainly in one of two ways: water is either heated until it evaporates (called a thermal process) or forced through a membrane that allows water molecules but not salt ions to pass (known as reverse osmosis). Oasys’s method uses a combination of ordinary (or forward) osmosis and heat to turn sea water into drinking water.
On one side of a membrane is sea water; on the other is a solution containing high concentrations of carbon dioxide and ammonia. Water naturally moves toward this more concentrated “draw” solution, and the membrane blocks salt and other impurities as it does so. The resulting mixture is then heated, causing the carbon dioxide and ammonia to evaporate. Fresh water is left behind, and the ammonia and carbon dioxide are captured and reused.
Oasys says the technology could make desalination economically attractive not only in arid regions where there are no alternatives to desalination, but also in places where fresh water must be transported long distances.
Thanks to Loretta Lohman for the link.