SODIS: Solar Disinfection of Water

SODIS solar disinfection of water is perhaps the cheapest and easiest to implement of all Andy’s projects: fill a bottle with water, leave it in the sunshine for a few hours, the water heats up, the parasites die.

I’ll get to the specifics in a bit, because it’s a bit more complicated than this, but consider the fact that most African villagers use charcoal (which means they cut down all the trees in their shamba) to make their water safe for drinking. Now consider that more women and children die in Africa each year from smoke than from malaria. No, I don’t mean cigarette smoke (thankfully, this is one category in which Africans are world leaders) but smoke from cooking fires, which is inhaled at close range by women and children on a daily basis. One-week old babies, wrapped tightly against mother’s back as she stirs the evening meal, are powerless to stop the smoke from entering and destroying their tiny lungs. Respiratory systems are severely damaged, leading to an overall reduction in immune system efficiency and an ultimate death from flu or pneumonia.

Can these deaths really be prevented just by putting bottles out in the sun? Andy believes so, and so do the thousands of villagers in the Iringa region who he has helped to begin purifying their water by using SODIS technology. Ideally, the bottle should be between 1 and 2 liters in capacity, and should be placed on a strip of corrugated metal to help the water heat up faster and more thoroughly. This allows the water to reach 30 degress C, at which point all harmful parasites die. Two hours of direct, hot sunshine will do the trick, but six is better.

But where can the villagers get corrugated metal and plastic bottles? Half the mud huts in these villages are roofed with corrugated metal, so there are always scraps lying around, and there just so happens to be a spring water-bottling factory (Maji Afrika) not 30km outside Iringa. These bottles are usually chucked from bus windows (like the blue plastic bags that blight the gorgeous African landscape) or into burn piles where they leach their poisonous chemicals into the atmosphere one way or another. So instead of degrading the environment with these bottles, we can actually beautify the land and save people’s lives while we’re at it.

Andy has introduced this concept to dozens of local schools, ensuring that each child places a full bottle of water on the roof of the classroom in the morning, so that when school ends he or she can take a bottle of clean water home for the night. Anette and I have been using SODIS here at home in Iringa for several months now, and we would like to help students at all 23 of FORS’ schools in Idodi and Pawaga to do the same thing.