sand layer height

[Guest]

#669

Hello, I\’m writing from the Comprehensive Rural Health Project in Jamkhed, India. CRHP is a non-profit NGO working in the field of community-based primary health and development in the remote areas of Maharashtra since 1970 (www.jamkhed.org). We have recently taken interest in the biosand filter as this technology appears to be appropriate to the water needs of village communities partnered with CRHP. One of the concerns, however, is the cost associated with the standard concrete filter (as described by CAWST). Although we believe it would be possible to produce these filters at around USD$12-15 the average individual in these areas earns $1-2/day. The filter would represent a significant investment and given the the people\’s unfamiliarity with this technology there may be reluctance.
So the question is whether decreasing the size (i.e. by using smaller ready-made plastic or metal containers) will significantly affect filtration efficiency. There have been some unofficial reports that a decrease in the height of the sand layer will not dramatically reduce filtration. If anyone has information regarding this issue please let me know as this will be a great help to our project and its current goal of improving the state of water and sanitation conditions in the villages.

[Eric]

#671

Hello

Please check the link http://biosandfilter.org/biosandfilter/index.php/item/289

Here you\’ll find information on the importance of both sand size and bed depth. Personally I believe that the concrete filter is as yet not deep enough – I would prefer 50-60cm sand depth rather than only 46cm. This is because there are filtration processes that happen with increased depth. There are people that argue that shallower bed depth is fine, and bacteriologically that may be the case since the biological population is fairly mobile and within the top layers. But for sure better filtration overall (biological, chemical, physical) happens when the sand is deeper than 40cm.

Eric

[Guest]

#672

It may be possible for people to make their own filters more cheaply. See the Home made biological sand filter design described on http://www.cms-uk.org/water. Depending on the local material cost it could be a lot cheaper for families to use this design which does the same job in the same way as the concrete ones do. Don’t be put off if you don’t have clay pots available as the cms pages include guidelines for making adaptations.