Water filter test summary

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.

All of the specific details regarding implementation of these concepts can be found in this blog, and the three other water filtration websites that are associated with it.

This entry was posted in slow sand water filter study and construction. Bookmark the permalink.

2 Responses to Water filter test summary

  1. First of all I’d like to say thank you for all the info you have posted so far .
    I built a slow sand filter out of a 50 gallon drum the water comes out very cloudy I purchased
    All the sand from lowes and used play sand as the main media iv tried
    Washing it several times so my question is did I use the wrong sand or is it just a matter of seasoning

  2. filter_guy says:

    Play sand will work, but it is very, very dusty. I have tried washing it. It takes a very long time to get the water running through it to show up clear. In your case, there could be clay like material embedded in the grains of sand that will gradually wash off as your filter runs, harmless to the function of play sand, but very annoying when it is used as filter sand. It will probably take a lot of water and good pressure to wash the sand off completely. Alternatively, you can just let the filter run until the water clears up. That may take weeks, to months.

    Another method I have tried, with much success, is to wash the sand I plan to use on a very fine stainless steel screen (60 mesh or 80 mesh) after putting small amounts in a 5 gallon bucket with enough water to just cover it, and then agitating it robustly so as to break loose embedded clay and silt. The stainless steel screen can be purchased on line very inexpensively from McNichols.

    Details of the stainless steel wire mesh:

    3860753610 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 60 Mesh, 0.0075″ Wire, .0092″ Opening, 36.0000″ Width

    3860754810 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 60 Mesh, 0.0075″ Wire, .0092″ Opening, 48.0000″ width

    3880554810 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Plain Weave Construction, 80 Mesh, 0.0055″ Wire, .007″ Opening, 48.0000″ width

    3850093610 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 50 Mesh, 0.0090″ Wire, .011″ Opening, 36.0000″ Width

    3850094810 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 50 Mesh, 0.0090″ Wire, .011″ Opening, 48.0000″ Width

    3140104810 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 316,
    Woven Construction, 40 Mesh, 0.0100″ Wire, .015″ Opening, 48.0000″ Width

    3840103610 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 40 Mesh, 0.0100″ Wire, .015″ Opening, 36.0000″ Width

    3840104810 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 40 Mesh, 0.0100″ Wire, .015″ Opening, 48.0000″ Width

    3830123610 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 30 Mesh, 0.0120″ Wire, .0213″ Opening, 36.0000″

    3830124810 McNICHOLS Quality Wire Mesh, Square Weave, Stainless Steel Type 304,
    Woven Construction, 30 Mesh, 0.0120″ Wire, .0213″ Opening, 48.0000″ Width

Leave a Reply

Your email address will not be published. Required fields are marked *


This blog is kept spam free by WP-SpamFree.