New Device Cleans Water With Light, Could Save Lives In Third World

January 24, 1996

By Mike Wooldridge (

BERKELEY, CA--Scientists at the Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a simple disinfection device that uses light to cheaply rid water supplies of cholera, typhoid and dysentery. The technology could save lives in third-world countries, where such waterborne diseases kill more than 400 children every hour.

The device takes water from a source--for instance, a community hand pump -- and passes it through a stainless steel disinfection chamber. Inside the chamber, the water is bathed in ultraviolet (UV) light, which kills viruses, molds and other pathogens by inactivating their DNA.

"The device has tremendous potential to save lives," says physicist Ashok Gadgil, a researcher in the Lab's Energy and Environment Division who is developing the device. "It gives communities in developing countries a central place for collecting disinfected water."

Last fall, Berkeley Lab researchers shipped devices to the Virgin Islands for disaster relief in the wake of devastating hurricanes that left much of St. Thomas and neighboring islands without safe drinking water.

The UV system is currently being field tested in India, where cholera epidemics in recent years have killed thousands of children. Heavy monsoon rains often lead to flooding that washes raw sewage into wells, contaminating water supplies.

"We're developing the device to be low-cost and low-maintenance, something that can be manufactured in the developing world." Gadgil says. The size of a microwave oven, the device can disinfect water at a rate of four gallons per minute--similar to what flows from a typical bathtub spout--at a cost of pennies per ton.

Scientists have known that UV light can disinfect drinking water since the early 1900s. Only recently, however, has UV technology become affordable enough for disinfection on a large scale.

UV light is most effective at a frequency of 254 nanometers, the same frequency of light given off by the standard mercury-vapor lamps sold in hardware stores. The UV equipment in the device is similar to the fluorescent lights found in homes and offices, except the device's lamp glass lacks the phosphor coating that converts UV energy to visible (non-UV) light.

The UV device has significant advantages over chlorine disinfection, a common way of disinfecting water in developing countries. Chlorine disinfection requires a trained person to make sure the levels of chlorine used are at effective levels; adding chlorine to water supplies can also add an unpleasant taste. Chlorine-based disinfection, however, is still be a better disinfection method in communities with a high incidence of giardia, another common infectious agent. UV light does not kill giardia.

The UV devices could have environmental benefits as well. In many third-world countries, water is disinfected by boiling it over inefficient, wood-burning stoves. Boiling a gallon of water to disinfect it consumes 20,000 times more energy than using the UV device. The UV device would lessen the need for wood resources and thereby reduce deforestation.

The system could also improve the quality of life for third-world women, Gadgil says. Women usually do the bulk of the family cooking chores, which includes gathering firewood and disinfecting drinking water. A UV device attached to pumps could free the women from these chores.

Gadgil's colleagues on the project include Berkeley Lab mechanical engineer Derek Yegian, engineering graduate student Todd Reynolds, visiting physicist Edas Kazakevicius of Lithuania, and postdoc Marc Fischer.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, Calif. It conducts unclassified scientific research and is managed by the University of California.