Ok, so what's wrong with making a filter that uses the clay we have discussed and the only other thing we have...fire.

http://info.anu.edu.au/mac/Media/Media_Releases/_2005/_January/_190105filters.asp

Thanks to TWheless for the article...very neat concept, should be a wonderful find for third world countries. My only question would be, does it have to be terracota clay? or will any clay that can be heated work?