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Ideas For India

Dec 01, 2004
Safe water from SODIS and SPOWTS

Two environmentally-soulful, low-cost technologies —SODIS and SPOWTS—are capable of producing safe drinking water from polluted water sources in remote areas. Both deliver sharp slaps on the notion of safe water having to come in priced bottles that are thrown away as litter.

For those of us, now made forgetful by electric UV-treated water units in our homes, here’s a quick primer on ultra violet rays [UV] and Ozone. The sun constantly radiates UV light, which if it enters the atmosphere unrestrained, is harmful to life. But luckily we have the ozone layer in the stratosphere. Ozone is a highly reactive form of oxygen and is equally destructive to life forms in large quantities. However, when UV meets the ozone layer, most of the former is blocked and absorbed. Which by the way, is the reason why we need an intact ozone layer. The purpose of this primer is to remind ourselves that diffused UV is everywhere around us in nature. When polluted water is exposed to UV or made to interact with ozone, harmful micro life forms are destroyed.

The Solar Water Disinfection Process [SODIS], a Swiss innovation, is simplicity itself. Polluted water is prepared for treatment by nominal filtering for sediments. Discarded plastic bottles are cleaned, partially filled with water that is to be treated and shaken vigorously, in order to oxygenate it. The bottles are then filled fully, closed and placed in full sunlight for between 6 and 8 hours. The combination of heat and oxygen-UV interaction kills all pathogens, rendering water safe for drinking.

Obviously SODIS works best in sunny climes— which are also places where safe drinking water is a concern. The process is helped by placement of a black sheet under the bottle to enhance heating. Also, PET bottles are better than PVC ones. It must be remembered chemical, toxic pollutants are not removed by this process.

SODIS is becoming popular in South America, Thailand and Kenya. In Kenya for example, people took quickly to the idea because their tradition was to wash and sun-dry utensils. Goes to show that when we go close to ‘native-ways’, a lot of good sense is revealed.

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