December 01, 2003

Professor sees solar solution to safer water

Cardboard and aluminum foil. Unlikely tools for curbing water-borne diseases – until you factor in sunshine and biology professor Robert Metcalf.

For 25 years, Metcalf has been touting the benefits of solar cooking as a cheap, sustainable fuel source for developing countries. But a series of laboratory findings by the microbiologist reveal it can also be a simple technique for killing harmful bacteria in drinking water.

When it comes to contaminated water, the usual advice from world health organizations has been “boil it.” Metcalf says that’s utterly impractical advice for the 2.5 billion people in the world, especially in Africa, who depend on traditional fuel such as wood or charcoal.

“They don’t have enough fuel to use it for boiling,” he says. What fuel they have is wood they’ve spent hours gathering or up to a quarter of their income to buy. Not only does Metcalf suggest that they use the sun for fuel instead, but contradicts conventional wisdom: “You don’t really need to boil it,” he says.

Just as milk doesn’t need to be boiled to be pasteurized, Metcalf’s work shows pasteurization of water can be accomplished by heating to 149 degrees Fahrenheit. And it’s a temperature that is easily reached with a solar cooker. “Most microbes in water are bacteria or viruses,” Metcalf says. “Water boils at 212 degrees, but heating it to only 149 degrees (65 degrees Celsius) will kill disease-causing microbes in water.”

About a dozen students have contributed to Metcalf’s pasteurization research. “We’re the world’s experts on this. It’s world-class stuff we’re doing,” he says. They also helped develop a simple, reusable device – a wax-based water pasteurization indicator or WAPI – that allows people in parts of the world where thermometers aren’t readily available to verify pasteurization temperatures have been reached.

For the last four summers, Metcalf has been taking his water act on the road to East Africa. This year, he and CSUS alum Christine Polinelli of the Australian Department of Health worked with the Sacramento-based non-profit Solar Cookers International to launch Sunny Solutions, a program in the Nyakach region of western Kenya that teaches people how to test their water and, if it shows signs of E. coli, how to solar-pasteurize it. A portion of their effort was funded by a CSUS research and creative activity grant.

“Out in the middle of nowhere we’re teaching serious microbiology that they can apply and understand. Through the method of teaching we use, they learn how a tiny microbe can become billions quickly and cause disease. It’s thrilling to be able to do that,” he says.

The information can help them make decisions about chlorinating water sources like wells or using solar cookers to pasteurize water. While in Tanzania and Kenya, Metcalf and Polinelli even solar-pasteurized their own drinking water.

One added bonus for the Sunny Solutions program is that once people see what the solar cooker can do for water purification, they see what it can do for cooking.

Metcalf says that most of the world’s 1.2 billion people who don’t have safe water also use even-scarcer fuel wood for cooking. Cooking using traditional fuel requires about two pounds per person per day, which ends up as ash. Wood fires also create tremendous indoor air pollution, equivalent to smoking three packs of cigarettes per day. In many fuel-scarce countries like Kenya, solar cooking and solar water pasteurization is possible 200- 300 days per year.

“The potential for spread and the sustainability of the project are enormous,” Metcalf says. “The reason so many us get into science is there are things we discover which can improve the human condition. Here’s something that can.”


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