According to this post from Treehugger,
An Australian inventor claims that a handful of clay, yesterday’s coffee grounds and some cow manure are the ingredients that could bring clean, safe drinking water to much of the third world. The simple new technology, developed by ANU materials scientist Mr Tony Flynn, allows water filters to be made from commonly available materials and fired on the ground using cow manure as the source of heat, without the need for kiln. The filters have been tested and shown to remove common pathogens including E-coli. Unlike other water filtering devices, the filters are simple and inexpensive to make.
I don’t need to go into the virtues of clean water… What a wonderfully simple innovation!