Corrected link below.

Interesting solution.

Reminded me of the backpackers knowledge of the possisiblity to draw water and drink from the top couple of inches of a still water lake at the end of the day as UV kills all of the bateria on top. For high mountain and alpine lakes the UV radiation can be significant

Thanks

http://www.seattletimes.com/business/technology/potavida-a-smart-water-purifier-for-people-in-need