Could Seawater Solve the Freshwater Crisis?
Experts weigh in on what's holding desalination back.
(Read National Geographic magazine's special water issue online.)
Scientists predict that by 2016, the amount of fresh water produced by desalination plants will exceed 10 billion gallons (38 million cubic meters) a year, or double the rate in 2008.
Modern desalination plants use a technology called reverse osmosis, pressing salty water through ultrathin, semipermeable plastic membranes. Unable to pass through, large molecules or ions, such as salt, are filtered out, so fresh water flows out the other side. (See diagrams of three proposed alternatives to reverse osmosis desalination.)
This method wastes much less energy than earlier desalination techniques, such as heating seawater and harvesting fresh water from the steam. But a typical reverse osmosis plant can still spend up to
