First; my humble apologies for being so slow to moderate comments. Vast improvement is in order. We have updated the software that runs the blog ( as of July 24 2009) which went perfectly. Moderating should be quicker now.
The slow sand filter works using biological processes. Water passes through a layer of sand and after about 3 weeks a layer of biological activity forms in the upper 2 to 3 centimeters of the sand. The bacteria in this layer sometimes called the “schmutzdecke” break down harmful bacteria such as “beaver fever cysts”, all coliform including the most deadly and the resulting water out of the filter is safe. A lively discussion about these filters would be very encouraging. Anyone who has comments, questions, or experience with these filters is encouraged to leave comments. The website http://www.shared-source-initiative.com/biosand_filter/biosand.html documents a year and a half of experience building and operating 2 of these filters built from mostly recycled materials. All tests so far have shown they work very well. Also the website http://www.slowsandfilter.org has more detailed information and an FAQ page.