GENEVA A do-it-your-self technique of disinfecting water with sunlight and soft-drink bottles could save hundreds of thousands of lives a year, according to the World health Organisation (WHO).

In a campaign to reduce deaths from unhealthy water in developing countries, the United Nations health agency is promoting a nearly cost-tree process called Solar Water Disinfection, or Sodis.

Requiring only sunlight, empty plastic soft-drink bottles and a black surface, it costs almost nothing, said Mr Martin Wegelin, a researcher at the Swiss Institute for Environmental Science and Technology.

The process is simple:

Transparent bottles are filled with water and placed horizontally on a flat surface for about five hours.

The heat and ultraviolet rays of the sun kill illness-causing micro organisms in polluted water.

Unlike the boiling of water, this method requires no fuel.

"Some 2.5 million people die from drinking unsafe water every year," said WHO director of the department of health and environment Richard Helmer.

‘They are unnecessary deaths, since this method could provide them with safe drinking water. This is a highly reliable method that has been proven to work."

The method is even more effective when the bottom half of the bottle is painted black or placed on a black sheet of corrugated iron or plastic. This allows more heat to be absorbed and kills more pathogens.

The simple process kills most micro organisms, but not all of them, and should only be used in very hot countries where the sunlight is intense, WHO officials said.

More than one billion people drink unsafe water, the agency said in a report to mark World Water Day.

A total of 3.4 million people. mostly children, die every year from water-related diseases from drinking, swimming in or washing clothes in polluted water.

Diseases include malaria, diarrhoea and guinea worm.

WHO urged the use of Sodis, chlorination and better hygiene as immediate means of improving water quality in developing countries.

It said chlorination is another simple method that costs just a few cents a day.

"Even in conditions of very poor sanitation and hygiene, where people are collecting whatever water is available for their household supply, if the water is chlorinated, it is improved," said Mr Mark Sobsey, professor of environmental microbiology at the University of North Carolina in Chapel Hill.

WHO said chlorine could be added to both home and city reservoirs and was essential in refugee camps.

Source : The Straits  Times, Mar 23, 2001

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