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Sunshine + plastic bottle = clean water

is plastic water bottle in the sun.
(Anna Jefferys/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."

Water board slow to adopt

Despite its benefits, SODIS officials at the Benin Water Board (SONEB) say they have not yet agreed to promote SODIS as an official strategy and will not openly state whether or not this will change.

"SODIS is advised only in cases where there is no drinking water. Where there is a good supply of drinking water, there is no problem," said one source close to the Beninese Ministry of Water who requested anonymity.

SODIS will not work without the right conditions in place. "Carefully washed bottles and clean hands are vital requirements,” said Adissoda. This involves high hygiene awareness levels, and public information campaigns can cost up to US$2 per person, she added.

The water itself cannot be too dirty in the first place - if it is too cloudy it might resist the sun’s rays. Finally, though cheap, plastic bottles are not always plentiful in rural areas. However, the most vital ingredient - sunshine - is abundant in countries such as Benin.

Meanwhile, officials at SODIS are trying to raise awareness of the method across the region, hoping that attitudes to it will change. This may be starting to take effect at Benin’s water board. Having been coy at first, another high-level official at SONEB told IRIN on condition of anonymity: "We believe that as we move towards covering the entire national territory with drinking water we should welcome the interest that SODIS can generate among the population of Benin."


This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions

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