| UV Waterworks
While Ashok Gadgil was growing up in India in the 1950s, water-borne disease killed five of his infant cousins. In 1993 a cholera epidemic struck India, and Gadgil, by then at Berkeley Lab, made up his mind to develop an effective water purifier.
Boiling water takes fuel, hard come by in rural India. Chlorination works well in centralized water systems, but the practical solution for Indian villages was ultraviolet light, which does not kill organisms outright but disrupts their DNA so they quickly die out without reproducing.
Most UV systems need pressurized water from heavy pumps that draw a lot of power. Gadgil knew that to serve poor rural populations, a UV water purifier would have to treat water that was hand pumped or even hand poured.
Gadgil began working after hours with scrounged parts and volunteer help. When the Department of Energy, the US Agency for International Development, and private sources provided grants, he was able to test a prototype UV water purifier in a few Indian villages -- he knew it was too heavy and too expensive, but he could fix that later. The biggest surprise was that it was too efficient! At eight gallons a minute, the villagers couldn't pour water into it fast enough, and it produced more clean water than they could use.