Freelance Fundraiser’s Jottings

6 September 2008

Sunshine + plastic bottle = clean water

Last night I went to see some profoundly deaf Tanzanian musicians and dancers perform at my daughter’s school. I also learnt about something so simple and virtually cost free, that could save the lives of millions of people across the Third World. It involves the use of used plastic drinks bottles and sunshine to get rid of 99.9% of water-borne bugs and provide safe drinking water. A Google search came up with this article on the process.

Photo: Anna Jefferys/IRIN
Water if placed in a plastic bottle in strong sunshine can be decontaminated in as little as six hours.

COTONOU, 10 July 2008 (IRIN) – The government of Benin aims to dramatically increase the percentage of Beninese who can access drinking water by 2015 and one organisation, the Regional Centre for Water and Sanitation (CREPA) hopes to close the gap with a simple solution requiring little more than sunshine and a plastic bottle.

Developed by the Swiss Institute for Environmental Science and Technology (EAWEG), the method, called solar water disinfection, or SODIS, uses the sun’s UV-A rays and heat to decontaminate water. So far, up to two million people in 20 countries have used it, though Benin is one of the few West African countries to trial the method.

With abundant sunshine CREPA officials say the SODIS method could significantly improve the region’s drinking water problems.

“From what we know about the benefits it brings to many people now, we believe SODIS will help inform the water strategies of the national authorities in many African countries as part of a framework to fight poverty,” said Yadjide Gbedo Adissoda, technical adviser and engineer at CREPA.

Just 41 percent of rural Beninese currently have access to clean water but the government hopes to bring this up to 67 percent by 2015 as part of the Millennium Development Goals.

Diarrhoea causes up to 17 percent of infant deaths in the country, according to non-governmental organisation Countdown to 2015, and worldwide it kills 2.5 million people each year.

How SODIS works

Most Beninese who are not on the water grid make do by purifying their water themselves – by boiling it, chlorinating it, or by filtering out the sediment.

The SODIS method is more straightforward. Users take a clear plastic bottle with a maximum size of three litres, fill it with water and put it on the roof or a corrugated iron sheet to soak up the sun’s rays. Between six hours and two days later, depending on the strength of the sun, the water should be purified.

According to officials at EAWEG, the sun’s UV-A rays kill the pathogenic organisms in the water while its heat has a pasteurising effect. The combined effect can kill up to 99.9 percent of the micro-organisms that cause cholera and diarrhoea.

“A significant number of coliform bacteria disappeared after the SODIS method was applied in laboratory tests,” said CREPA’s Adissoda. According to SODIS’s impact studies, diarrhoeal infection rates drop by between 20 and 70 percent when the method is applied.

The method is cheap – bottles cost about six US cents each and can be reused if well kept, and it is safe – so far studies have not shown any risks of the plastic diluting into the water, according to Adissoda.

And the taste is chemical-free. “This water tastes really good,” said Gnona Marthe, a resident of Sèkandji village on the outskirts of Cotonou, where villagers are trialling the SODIS method.

Jean Yadouléton, director of CREPA, confirmed this, telling IRIN, “When they compared the water treated by SODIS with what they were accustomed to consuming, they noted a considerable difference in taste.”


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