Researchers at Boston University have developed ultraviolet (UV) light-emitting diodes (LEDs) to purify and disinfect water, according to a report posted on Electronics News. The new technology will be a lower cost, lighter, more durable alternative to mercury lamps which could mean wider distribution in developing countries. It also means no mercury to deal with.
There is a video on the link showing how it works.
I already have a clean water supply and purification tablets. Not sure I am ever going to need UV light-emitting diodes but I plan on buying a camping stove (Thank you Les Stroud) to boil water, among other things.