SODIS is one very simple way to produce safe drinking water. All you need is a colour-ess PET-bottle, some clear water and sunny weather. Sounds to easy? Various studies of highly reputated universites through out the world have proved, that the SODIS-method significantly improves drinking water qualitiy. Laboratory tests have shown, that in (sub-) tropical regions, six hours of sunlight* are sufficient to remove almost all germs in the water. Even the World Health Organisation (WHO) is recommending SODIS for potable water production. So why don't you give it a try?

A glance at history

In the 1980s, a Lebanese researcher discovered that the radition of the sun can disinfect water. Despite this magnificent discovery, there was no public interest in this procedure at this point. However, the 'EAWAG' institute in Switzerland seized the idea in the 1990s and conducted a number of tests to prove the efficiency of solar water desinfection. Studies conducted by highly esteemed universities confirmed that sunlight kills viruses, bacteria and pathogens. Furthermore, the procedure was declared to be medically adequate, hence sunlight-treated water was eventually potable water approved. Based on these results, a standard SODIS-method was definded. Over the years, the EAWAG team developed and tested different strategies to disseminate the idea in developing countires. As for now, professionals are working around the world to conduct trainings and promotion in order further disseminate the knowledge on SODIS.

How does it work?

When you lay in the sun for six hours, you skin will get sun-burned. The direct radiation of the sun is just too strong and your skin cells will get damaged. The same radiation will also destroy germs (like bacteria) in the water. When you put a bottle of water in the sun for six hours, e.g. on th house roof of your house, almost every bacteria is going to be killed.

The chemical process roughly looks like this: The so-called UV-Radiation produces reactive oxygen particles in the water and destroys the cell structure of germs. As the water also gets heated up during solar exposure, the disinfection process is further accelerated. Within six hours, SODIS typically reduces concentrations of pathogenic bacteria by 99.9-99.99%, and you can enjoy your first cup of sun-cleaned water.

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Is it really safe?

Yes, it is. Otherwise, highly reputated institutes (like the WHO) wouldn't have approved SODIS for daily use. Millions of people are using SODIS already and are very fine with it. If you follow the introduction carefully, there risk of getting diarrhoea decreases significantly.

"The jury considers SODIS an impressive way of contributing by the simplest means to making water supplies better and safer, thereby reducing diarrhoea and other diseases like it, and mortality in developing countries" (Red Cross Prize, 2006)

What is important when using SODIS?

• Use only clean and well-preserved PET-Bottles -  no PVC- / Glass- or coloured-Bottles!
• Use only clear water only - if the water is to murky, you have to filter it before using SODIS.
• SODIS does NOT remove chemical pollutans!
• DO NOT place the bottle in an upright position - it always has to lay down horizontally (see picture above)
• DO NOT use bottle greater than two litre
• DO NOT use SODIS for babies! They are ver sensitive and must only get sterile (freshly boiled) water! However, SODIS water is always preferable over untreated water.

Where can I get more information?

The best source is definitely the SODIS-Webpage. It contains detailed information about the SODIS-Method itself, the (project) development and the background story. There are also several studies listed. Info & Training material is available in various languages, including Kiswahili.

TAREA is not only promoting issues concerning energy, but also more viable uses of solar power. That is why we recommend SODIS in Tanzania. We would like to thank the SODIS-Team for their kind help creating this article!