More Information What is a Biosand Filter? A biosand filter BSF is an adaptation of the traditional slow sand filter, which has been used for community drinking water treatment for years. The biosand filter is smaller about 1 m tall, 0. The filter container can be made of concrete or plastic. It is filled with layers of specially selected and prepared sand and gravel. The sand removes pathogens and suspended solids from contaminated drinking water.
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History[ edit ] The household biosand filter was proposed by Dr. David Manz in the late s at the University of Calgary , Canada.
The Canadian non-profit company Center for Affordable Water and Sanitation Technology CAWST was co-founded in by David Manz and Camille Dow Baker to promote education and training in water purification and sanitation including using this technology, and to continue developing it. Below this, the diffuser plate prevents disturbance of the biofilm when water is poured into the filter. Water then travels through the sand column, which removes pathogens and suspended solids.
Below the sand column, a layer of gravel prevents sand from entering the drainage layer and clogging the outlet tube. Below the separating layer is the drainage layer consisting of coarser gravel that prevents clogging near the base of the outlet tube. These processes include: Mechanical trapping: Suspended solids and pathogens are trapped in the spaces between the sand grains. The flow rate slows because there is less pressure to force the water through the filter.
The inlet water contains dissolved oxygen, nutrients, and contaminants. It provides the oxygen required by the microorganisms in the biofilm. Large suspended particles and pathogens are trapped in the top of the sand and partially plug the pore spaces between the sand grains.
This causes the flow rate to decrease. Most removal occurs where water is in contact with the biofilm. The processes that occur in the biofilm have not been identified. Ideally, this should be high enough to keep the biofilm in the sand layer wet and allow oxygen to diffuse through the standing water to the biolayer.
The rate of flow through the filter is restored as they are consumed. If the pause period is too long, the biolayer will consume all of the pathogens and nutrients and will die, reducing the efficiency of the filter when it is used again. The pause period should be between 1 and 48 hours. As more water is poured, a biofilm forms along the top of the diffuser plate. Both of these occurrences cause a decrease in flow rate clogging and bioclogging. If flow rates fall below 0. About 1 US gallon 3.
The upper layer of sand is then swirled in a circular motion. Dirty water from the swirling is dumped out and the sand is smoothed out at the top. This process is repeated until flow rate is restored. The program includes visits to the beneficiary homes after one, three and twelve months and another at 5 years from installation date.
During each visit, beneficiaries receive repeated instruction about safe water practices and how to take care of the filter. Turbid water contains sand, silt and clay. In a study water was obtained from sample taps of water treatment plants from three local reservoirs. It poured through a slow sand filter and results showed that turbidity decreased to a mean of 1. The removal after this time ranged from The addition of primary effluent or waste water facilitates growth of the biofilm which aids bacterial die-off.
In research conducted in 55 households of Bonao , Dominican Republic, the average E. It removed This removal was comparable with that of the slow sand filter. Such health perceptions on the use of biosand filter has shown to be more positive in long-term users.
Concrete is generally preferable to other materials because of the low cost, wide availability and the ability to be constructed on-site. Several versions have been developed. Although the filtered water passes EPA water quality standards, it is not optimal. The CAWST Version 10 biosand filter takes this into account; the volume of the water reservoir is equal to the pore space volume of the sand layer.
Clean Water for Haiti, a non-profit organization based in Camp Marie, Haiti manufactures the biosand filters using an adaptation of the steel mold. The plans for a Wood Mold are openly available on the OHorizons website.
Hydraid biosand filters are constructed from medical grade plastic with ultraviolet resistance. The high cost of plastic prevents its use in rural India. The stainless steel filter, called JalKalp, offers increased filtration rate and better portability than concrete models and better production quality control.
Common quality issues are variations in construction material and manufacturing flaws. Further, the efflorescence due to salts in water reduces the life of the concrete filter. The newly developed lightweight 4. Besides improving its appearance, stainless steel adds to the strength, reliability, durability, and portability of the filter. This filter integrates the germicidal properties of copper with the conventional filtration.
S M Sehgal Foundation  promotes the model, which required no electricity, across India through partnerships with like-minded organizations to benefit as many rural families as possible. Many lack the professional capability of constructing the metal forms to pour the concrete into. Finding proper mesh sizes to sift the sand layers may also be absent. In Nicaragua you may find metal workers capable of welding rebar for home construction, however, you will not find sheet metal bending equipment to create the metal molds.
Sand is not sold in hardware stores like in the United States. When traveling to a third world country it might be best to take with you the proper mesh screens. Another problem facing the use of the filters is adoption. Many projects may provide assistance in building the water filters and some may even distribute them but getting the host country nationals to use the filters requires much more dedication.
People need to be connected to water filter owners to insist they use the devices and get them into the habit of using them. Otherwise several of the filters are abandoned and left unattended in the roads. Simply handing the filters out is insufficient for adoption. Sobsey Reduction of E. Water Research, Volume 42, Issues
The Biosand Filter
History[ edit ] The household biosand filter was proposed by Dr. David Manz in the late s at the University of Calgary , Canada. The Canadian non-profit company Center for Affordable Water and Sanitation Technology CAWST was co-founded in by David Manz and Camille Dow Baker to promote education and training in water purification and sanitation including using this technology, and to continue developing it. Below this, the diffuser plate prevents disturbance of the biofilm when water is poured into the filter. Water then travels through the sand column, which removes pathogens and suspended solids. Below the sand column, a layer of gravel prevents sand from entering the drainage layer and clogging the outlet tube. Below the separating layer is the drainage layer consisting of coarser gravel that prevents clogging near the base of the outlet tube.
Download Step Assemble! No need for glue yet; just a dry fit for now; gluing comes next. Leave the top lid off. Place an end cap on each collection tube. Connect each collection tube to one of the press fit elbow joints.