New water filter may help developing world

PALO ALTO, Calif., Aug. 31 (UPI) -- U.S. researchers using nanotechnology say they've created a high-speed, low-cost filter that could be used to purify drinking water the in developing world.

Scientists at Stanford University dipped plain cotton cloth in a high-tech solution of silver nanowires and carbon nanotubes to create a filter that kills rather than traps harmful pathogens, a university release says.

Instead of stopping bacteria as most filters do, the new filter lets them through with the water -- but they're no longer a health threat, because the filter kills them with an electrical field that runs through the highly conductive "nano-coated" cotton.

In lab tests, more than 98 percent of E. coli bacteria exposed to 20 volts of electricity in the filter for several seconds were killed.

Multiple layers of fabric were used to make a filter 2.5 inches thick.

"This really provides a new water treatment method to kill pathogens," Yi Cui, an associate professor of materials science and engineering, said. "It can easily be used in remote areas where people don't have access to chemical treatments such as chlorine."

Since the new filter doesn't trap bacteria, it can have much larger pores, allowing water to speed through at a more rapid rate.

"Our filter is about 80,000 times faster than filters that trap bacteria," Cui said.