A better way to make seawater drinkable

UCLA researcher develops efficient membrane for filtering out salt and impurities; nanoparticles do a lot of the work.

Researchers at University of California at Los Angeles have come up with a membrane that can filter salt and impurities out of seawater more efficiently and for less money than current systems, which potentially could help with the world's looming water problems.

The membrane, developed by Eric Hoek, consists of a matrix of porous polymer sheets embedded with specially designed nanoparticles. The nanoparticles attract water molecules and repel other particles. In reverse osmosis, seawater passes through porous membranes. The pores allow water to pass, but are too small for salt and other particles, thereby purifying the water.

The nanoparticles, because they attract water and repel other substances through their inherent chemical properties, cut in half the amount of energy required to pump the water through the membrane. That in turn could cut the cost of turning seawater into drinking water by around 25 percent.

Conventional reverse osmosis membranes also become fouled over time by the particles they filter out. Hoek's membrane doesn't need to be cleaned as often. Lower cost and easier maintenance could make desalination more attractive. It costs about 50 cents per cubic meter to desalinate water, according to industry estimates.

Several scientists believe that the world will face significant water problems in the relatively near future. Water consumption exploded in the last century with the growth in global population. Lining up for water has become a common practice in some neighborhoods in New Delhi. Lack of adequate water supplies could cause the spread of diseases, impede economic growth and cause crop yields to shrink, according to some researchers.

General Electric, Siemens and a number of start-ups in Israel have entered the market for water purification technologies in recent years. (The United Nations in fact recently wrapped up a conference on desertification in Israel.)

Desalination plants are being studied, or already are under construction, in India, Europe, Australia and the U.S., among other regions. A $250 million plant that will ultimately churn out 100 million cubic meters of water annually for human consumption opened in Ashkelon in southern Israel in August. It's the largest facility of its kind in the world. By 2020, Israel expects to desalinate 750 million cubic meters annually.

In Singapore, meanwhile, the government has begun a program of turning wastewater into drinking water in its euphemistically named NEWater project. NEWater will constitute 2.5 percent of the country's potable water by 2011.

UCLA is one of the world's academic centers for water research. Professors and engineers there in the 1960s and '70s performed the first large-scale tests of reverse osmosis.

"We, as a nation, thought we had enough water, so a decision was made in the 1970s to stop funding desalination research," Hoek said in a prepared statement. "Now, 30 years later, there is renewed interest because we realize that not only are we running out of fresh water, but the current technology is limited."

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