[yefragetuwrabrumuy]

There is a very inexpensive, effective and reliable filter that was long used in old Mexico. If you take a large block of limestone, hollow out its interior, and carve the lower side to a point, many contaminants are eliminated as water slowly seeps through the rock. Calcium and sometimes magnesium are added.

This is what it looks like in practice:

http://www.youtube.com/watch?v=OvwtpbMF3v0

Here is a two stage limestone filter:

http://i.imgur.com/SecVESo.jpg

[neverdem]

Thanks for the links!