Forward Osmosis

Engineers should not causally accept the idea of trading energy for water.  Commercial desalination is usually done in one of two ways.  The first, known a thermal desalination, involves boiling seawater to 212 F, 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 - - increasing water needs in an era where energy demand is projected to increase by 50% by 2035 (and after the events over the weekend in Japan, don't expect nuclear power to fill our needs gap)..

Given the ugly trade of energy for water - - in steps ex-Navy diver and Yale PhD environmental engineer Robert McGinnis.  His firm, Oasys Water, based in Boston has developed what is known as forward osmosis.  McGinnis claims his technology is at least 10 times more energy efficient than conventional methods.  McGinnis has 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 122 F to burn off salts and leave behind pure water, instead of the much higher temperatures required for thermal desalination.

Keep an eye on McGinnis and Oasys Water - - a clever idea that solves a real and pressing problem.