Energy efficient osmosis for desalination  

Cleantech.com has a report on a new, energy efficient, desalination process developed by a Yale University spinoff- Oasys develops energy-efficient osmosis for desalination.

U.S.-based Oasys said it has developed a low-cost, low-energy desalination and purification technology for seawater, wastewater and industrial waste streams.

The Yale University spin-out is currently seeking venture funding for its 'engineered osmosis,' a technology the company says reduces the energy needed to purify water to one-tenth of what's required by current desalination systems.

Many desalination systems employ reverse osmosis, which uses uses pressure or heat to force water through a semipermeable membrane.

Oasys is using forward osmosis, in which a draw solution of high concentration induces a net flow of water through the membrane, also called an osmotic pressure gradient. That process has low energy requirements but can sometimes require a second step of purification, using energy-intensive reverse osmosis or the direct removal of draw solutes.

Oasys said it has identified a concentrated solution that can be removed easily and completely during the second step of purification. That solution is ammonia and carbon-dioxide gases dissolved in water.

Oasys said its forward osmosis system uses a common membrane and a re-usable solution. The company estimates its process will cost $0.37 to $0.44 per cubic meter at commercial scale.

Israel issued a tender today for its largest-ever seawater desalination plant capable of producing 150 million cubic meters (39.6 billion U.S. gallons) of water a year.

The 2 billion shekel ($513 million) plant is planned for the western Soreq region, south of Tel Aviv near the Mediterranean, to address the water shortages exacerbated by recent low rainfall and negotiations with Palestine and Syria.

The country's Finance Ministry said four groups are expected to submit bids to build and operate the plant before transferring it to the state.

The country already has two desalination plants operating in central and southern Israel that jointly produce 130 million cubic meters of water a year. The government plans to expand the capacity to 187 million cubic meters.

A third desal plant is scheduled to be commissioned in the city of Hadera later this year. The cost of the 100 million cubic-meter plant is estimated at 1.5 billion shekels.