Friday, August 14, 2009

solar water treatment

Our drinking water comes from the well, treated with a solar disinfection process (SODIS) as developed by the Swiss Federal Institute of Aquatic Science and Technology and Sandec Department of Water and Sanitation in Developing Countries. SODIS is recommended by the World Health Organisation and is promoted throughout the developing world as a simple, low-cost technology with great potential to improve the health of those without access to safe drinking water. The SODIS process is a simple technology that uses solar radiation to destroy pathogenic microorganisms which cause water borne diseases. Sunlight treats the contaminated water through two synergetic mechanisms: radiation in the spectrum of UV-A (wavelength 320-400nm) and increased water temperature. If the water temperatures raises above 50°C, the disinfection process is three times faster.

Transparent 1.5L plastic (PET) bottles are filled with well water and exposed to full sunlight for six hours (minimum), on a sheet of corrugated iron.
Ah, but what about the nasty chemicals from the plastic I hear you cry…? Sunlight transforms plastic material into photoproducts. Laboratory and field tests however revealed that these photoproducts are generated at the outer surface of the bottles. No migration of these photoproducts from the PET bottles into the water was observed with the applied analytical methods.

It is a clean, green and simple technique for water treatment that sure beats boiling.

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thanks for taking the time

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