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February 24, 2012

Solve For X - Desalination with Forward Osmosis

Global water scarcity presents a grave challenge to continued human development and sustainability. The answer, however, is to use more water, not less. In order to do this, a dramatic technological breakthrough in desalination is necessary. This presentation describes the beginning of that effort.

Rob McGinnis is Co-Founder and Chief Technical Officer of Oasys Water where he's developing forward osmosis desalination technology.

Business Week - Commercial desalination is usually done in one of two ways. The first, known as thermal desalination, involves boiling seawater above 212F, then distilling the vapors. The second, called reverse osmosis, uses hydraulic pressure to force water through a membrane that filters out salt. Both require enormous amounts of energy. McGinnis says he's found a method that's at least 10 times more fuel-efficient.

Water molecules naturally want to flow from fresher solutions to saltier ones. Hence the "reverse" in reverse osmosis: It forces water molecules to go against their tendency. McGinnis's method makes use of forward osmosis. He's developed a "draw solution" that's saltier than seawater. Without need for any energy, the water molecules in seawater flow across a porous membrane and into the draw solution, leaving the sea salt behind. McGinnis's solution is as undrinkable as ocean water, but its salt compounds—"essentially just ammonium, carbon dioxide, and some other secret stuff," he says—vaporize at lower temperatures. McGinnis's solution needs only 122F to burn off salts and leave behind pure water, instead of the much higher temperatures required for thermal desalination.




Global Challenges in Energy and Water Supply: The Promise of Engineered Osmosis




After graduating from Yale with a PhD in environmental engineering in 2009, McGinnis co-founded Boston-based Oasys Water and raised $10 million from three venture capital firms to commercialize the technology, including developing a thin membrane suitable for forward osmosis. Oasys plans to start taking orders in late 2011. "Forward osmosis is on the verge of becoming a buzzword," says Tom Pankratz, director of the International Desalination Assn. "Oasys has a clever approach. ... It could potentially be used not only for seawater desalination but also treating wastewater."

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