After 4 years of college where I learned (hopefully) how to write about what I observe; and following that, close to 7 years of designing, building, studying, and operating small scale slow sand water filters (often called biological sand water filters); some information has become self-evident:
1. With some basic understanding, common sense, and willingness to pay attention to simple maintenance; It is possible to produce extremely high quality water with a “do it yourself” small scale biological slow sand water filter.
2. Continuous flow of water from the same source through a small slow sand filter will result in the highest quality output. (use an overflow to capture the water that does not flow through the filter immediately, and then just re-introduce it again, no fancy expensive high tech stuff is needed if the operator is willing to add the water manually)
3. Finer sand in a small slow sand filter produces the highest quality output as compared to coarser sand, which does not.
4. A slow flow through a small biological sand water filter produces the best output as opposed to a rapid flow, which does not.
5. Thoroughly washed sand produces better output water, than un-washed sand.
6. It is possible to sift your own sand using inexpensive commonly available sand, resulting in sand size quality that comes close to duplicating “manufactured filter sand”.
7. The output from a “do it yourself” small slow sand filter will vary considerably, depending on the surroundings, input water, and attention to maintenance.
8. Highly turbid (cloudy) water will clog a small slow sand filter very quickly; within days, or even hours.
9. “Cleaning” a small slow sand filter by “wet harrowing” is very easy and takes very little time.