permaculture

[Lawrence London <lfljvenaura@gmail.com>]

http://www.cawst.org/en/themes/biosand-filter

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<http://www.cawst.org/>Themes<http://www.cawst.org/en/themes/the-need-for-clean-water>Biosand
Filter
 Biosand filter

 *What is the Biosand Filter?*

 The biosand filter (BSF) is an adaptation of the traditional slow sand
filter, which has been used for community drinking water treatment for
almost 200 years. The biosand filter is smaller (about 3 feet tall and 1
foot wide) and adapted for intermittent use, making it suitable for use in
people’s homes. The filter container can be made of concrete or plastic and
is filled with layers of specially selected and prepared sand and gravel.
The sand layer removes pathogens and suspended solids from contaminated
drinking water.



[image: Biosand_filter]
*
History of the Biosand Filter*

 Dr. David Manz developed the household biosand filter in the 1990s at the
University of Calgary, Canada. Dr Manz has trained many organizations on the
design, construction, installation, operation and maintenance of the biosand
filter. He also co-founded CAWST in 2001 to provide the professional
services needed for the humanitarian distribution of the filter in
developing countries.

 As of June 2009, CAWST estimates that over 200,000 biosand filters have
been implemented in more than 70 countries around the world.
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How Does the Biosand Filter Work?[image: before_and_after_water_glasses]*

Contaminated water is simply poured into the top of the biosand filter on an
intermittent basis. The water slowly passes through the diffuser and
percolates down through the biolayer, sand and gravel. Treated water
naturally flows from the outlet tube.

 Pathogens and suspended solids are removed through a combination of
biological and physical processes that take place in the biolayer and within
the sand layer. These processes include: mechanical trapping, predation,
adsorption, and natural death.
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How Well Does the Biosand Filter Work?*

* *

CAWST has prepared a summary of laboratory and field studies for the biosand
filter. It has been proven to remove the following from contaminated water:

   - Up to 98.5% of bacteria
   - Up to 99.9% of protozoa
   - Up to 95% of turbidity
   - 90-95% of iron

Summary of Field and Laboratory Testing for the Biosand
Filter<http://www.cawst.org/en/resources/pubs/file/41-field-and-lab-testing-for-bsf>

Although the water may look clear after filtration, it is still necessary to
disinfect it to ensure the best drinking water quality possible. The biosand
filter removes most, but not all of the bacteria and viruses. The most
common methods used around the world to disinfect drinking water are:

   - Chlorine disinfection
   - Solar disinfection (SODIS)
   - Boiling

 For more information about the biosand filter and disinfection options read
the following documents:

HWTS Fact Sheets (all) - Simplified [ENG]
<http://www.cawst.org/en/resources/pubs/file/36-hwts-fact-sheets-simplified-english>
Project BRAVO - A Field Study in Haiti Executive
Summary<http://www.cawst.org/en/resources/pubs/category/7-peer-reviewed-research?download=31%3Aproject-bravo-a-field-study-in-haiti-executive-summary>
Project BRAVO - A Field Study in Haiti
Presentation<http://www.cawst.org/en/resources/pubs/category/7-peer-reviewed-research?download=32%3Aproject-bravo-a-field-study-in-haiti-presentation>
Biosand Filter Manual (Complete)
[ENG]<http://www.cawst.org/en/resources/pubs/file/43-pi-for-bsf-manual-complete-english>
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