No More Clean Water

Perhaps the greatest threat to the world is the possibility of running out of clean water. Right now, one out of every two hospital beds in the world is occupied by someone suffering from a water-borne illness. In terms of consumption, since 1950, the world population has doubled but consumption of water has tripled.

Three hundred million people now get their water from the sea or from brackish groundwater that is too salty to drink. That's double the number a decade ago. Desalination is a treatment alternative - - not a cheap way to get water, but sometimes it's the only way there it. Look to three technologies with the promise to reduce energy requirements of desalination by up to 30 percent - -

• Forward Osmosis (On the market: 2010 - 2012) - - Water molecules migrate by natural osmosis, without energy input, into an even more concentrated "draw solution," whose special salt is then evaporated away by low-grade heat.
• Carbon Nanotubes (On the market: 2013 - 2015) - - An electric charge at the nanotube mouth repels positively charged salt ions. The uncharged water molecules slip through with little friction, reducing pumping pressure.
• Biomimetics (On the market: 2013 - 2015) - - Water molecules pass through channels made of aquaporins, proteins that efficiently conduct water in and out of living cells. A positive charge near each channel's center repels salt.