Purifying Water For A Penny A Ton

MORE THAN TWO-THIRDS of the world's people still go outside their homes to fetch water--water that is often tainted with bacteria and other harmful micro-organisms. The World Health Organization reports that waterborne diseases such as cholera, typhoid fever, and dysentery kill more than 400 children an hour in developing countries.

Searching for an affordable remedy, researchers at Lawrence Berkeley Laboratory, an Energy Dept. lab in Berkeley, Calif., have developed an efficient ultraviolet-light system that is capable of purifying a ton of water for just 1 cents. Physicist Ashok J. Gadgil estimates that a $500 unit could supply 2,200 people.

Gadgil crafted a steel box lined along the top with fluorescent tubes lacking the usual phosphor glazing that normally would absorb UV light. The lamps purify the water passing below by exposing it to ultraviolet radiation.

Water that goes in with 1,000 units of E. coli bacteria per milliliter comes out completely free of E. coli. The system is capable of churning out about 7 gallons of clean water a minute.

Because UV light does not kill giardia or cryptospiridium, intestinal parasites, Gadgil recommends using a sand filter to stop them in areas where they are a problem. Prototypes are being field-tested in India with funding from U.S. agencies and private philanthropies.