on this frrum http://pub1.ezboard.com/fhoodlumsquestionsandanswers.showMessage?topicID=2959.topic they have started a topica about waterpurification by sun 2.
I don't really get using the UV-light, as far as i understand from a few links on that post is that you can kill bacteria by simply fill a thin layer of water in a transparant container and lay it in the sun... don't trust it, and it doesnt kill gairdia and stuff....