Water filters

Types

 * Instructions for making a water filter from gravel, sand, grass and a plastic bottle: UV_Water_Purification
 * UV LEDs can be used to kill pathogens and are cheap. The 'Pure Bottle' uses a hand-powered UV bulb: ]. Steripen is similar: . An open-source version of these would be nice.
 * Slow sand filter with layers of fine sand at the top, coarse sand in the middle and gravel at the bottom.
 * According to research by Micha Hummler: Original Plans from Josh Kearns and Aqueous Solutions: *http://www.aqsolutions.org/
 * Here is a $90 DIY water filter for purifying rainwater to drinking quality. Bill of materials and instructions are included (CC-SA license): http://www.aqsolutions.org/images/2008/05/bucket-filter.pdf
 * Ceramic Water Filter: http://other90.cooperhewitt.org/Design/ceramic-water-filter
 * Potters For Peace - Water filters
 * Potters For Peace on colloidal silver for water filters
 * charcoal filter: inexpensive and very effective (but need to make sure that there are no residual volatiles in the charcoal); can later be reused as biochar