Using the sun to sterilize water

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We have shown various ideas for water purification in the third world, but this sure is a simple one- Fill plastic bottles, sit them on a black roof and leave it for a day. The sun heats the bottles and a combination of bacteria-killing ultraviolet light and the heat sterilize it. "The technology is very easy, but up to now people have not been told about it. We can use old pieces of roofing to put the bottles on. It is also very cheap, so is accessible to everyone." ::BBC via ::Ecofriend

read John's post on elegant, simple solutions and other posts on water