Slow sand filtration information

For the past eight years we have been building, testing, and operating small slow sand filters. What we have discovered here coincides very closely to some of what is covered in this document published by the State of Washington in 2003.  If you are interested in finding out more about slow sand filtration, this document is excellent. There is more information for larger filters in the pdf at the link to the 2003 document, but the theory of operation is basically the same for the smaller filters we describe here at this location.