New Device Cleans Water With Light, Could Save Lives In Third World |
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January 24, 1996 |
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By Mike Wooldridge (MAWooldridge@LBL.gov) |
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.