Explains turbidity, how to treat it, and most importantly provides a cheap way to build a turbidity tube with household materials.

Explains the use of the secchi disk, a common tactic in determining turbidity of water.

Another listing of different purification methods. Includes others not noted in the HoWF website and contains simple, useful visual aids.

2008 WHO Report on the international water crisis. Provides a look at various diseases and contaminants of concern, as well as solutions and other facts in relation.

A catch-all, scholarly view of the international drinking water issue. Outlines clearly the various pathogens/diseases that give cause to the water purification mission, as well as chemical contaminants, global impact and possible solutions. Lengthy, but relevant read

The site provides an in-depth look at different methods of water purification, including distillation, reverse osmosis, and filtration. While the information is geared towards promoting the filtration option, it's almost 100% objective and provides a lot of detail.

Good descriptions and tables of various kinds of water filters, with charts to provide visual aid.