Tuesday, May 18, 2010

Solar Water Disinfection

I stumbled upon this article on solar water disinfection, SODIS for short. This seems a simple and reliable way to disinfect smaller amounts of water. Cheap and reliable. I would not necessarily want to use it for daily water consumption, but it seems a great way for emergency situations such as water shortages in a crisis situation or on a hiking trip. Glass unfortunately does not work as well as PET bottles. UVA has a wavelength of 400 nm to 315 nm, UVB ranges from 315 nm to 280 nm. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm, meaning that window glass blocks a bit more than the lower half of the UVB wavelength range. This research data by Waste and Resources Action Programme would indicate that transparent wine bottle can be used. According to this roughly 90% of all UVA passes through, while all UVB is blocked. Maybe additional exposure time to sunshine can compensate for the UVB blocking of glass in comparison with PET.

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