Resources for Leaders

A plastic (PET) bottle provides a cheap way to harness the power of the sun to disinfect emergency supplies of drinking water. The idea of using plastic bottles for solar disinfection -- or SODIS -- has been developed by researchers at the Swiss Federal Institute for Environmental Science and Technology in Duebendorf.

To disinfect water, simply fill clear plastic (PET) bottles with water and leave them in the sun.

The heat warms up the water and the combination of warm water and ultraviolet radiation kills most microorganisms. Tests have shown that 99.9 per cent of the Escherichia coli in a sample of contaminated water were killed when the sun heated the water beyond 50ºC. At this temperature, the process can take as little as an hour. Painting half the bottle black and laying it on a corrugated metal sheet shortens the time taken to warm up the water.