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[[Image:CAWST_Kachan.png|thumb|right|150px250px| Cross-section through a Kachan Arsenic Filter]]
The Kanchan Arsenic Filter (KAF) is an adaptation of the biosand filter (BSF). It is based on slow sand filtration and iron hydroxide adsorption principles. The KAF has been designed to remove arsenic from drinking water, in addition to providing microbiological water treatment. Arsenic removal is achieved by incorporating a layer of non-galvanized nails in the diffuser basin of the filter.
This filter was developed by researchers at Massachusetts Institute of Technology (MIT), Environment and Public Health Organization (ENPHO) of Nepal, and Rural Water Supply and Sanitation Support Programme (RWSSSP) of Nepal.
==Suitable conditions==
It is suitable to process batches of 12-18 litres. If two batches a day are filtered, this provides 24-36 litres of clean water.
{{procontable | pro=
- Changing water sources (esp. to rainwater) may compromise removal of arsenic <br>
}}
==History and social context==
This filter was developed by researchers at Massachusetts Institute of Technology (MIT), Environment and Public Health Organization (ENPHO) of Nepal, and Rural Water Supply and Sanitation Support Programme (RWSSSP) of Nepal.
==Suitable conditions ==
It is suitable to process batches of 12-18 litres. If two batches a day are filtered, this provides 24-36 litres of clean water.
{{Potential_Treatment_Capacity_table
}}
==Technical specificationConstruction, operations and maintenance==
The filter container can be constructed out of concrete or plastic. The container is about 0.9 m tall and either 0.3 m square or 0.3 m in diameter.
Sand and iron nail selection and preparation are critical to ensure flow rate and treatment. Filters should not be moved after installation.
====Manufacturing====
Local production of filters is most common. Molds can be borrowed, rented, bought or constructed locally. Filters can be constructed at a central production facility, or in the community. Filter sand and gravel can be prepared (sieved and washed) on-site or nearby.
Materials and facilities required are:
*Steel mold
*Sand, gravel, and cement
*Filter sand and gravel
*Copper or plastic outlet tubing
*Metal or plastic for the diffuser basin
*5-6 kg of non-galvanized iron nails
*Metal or wood for the lid
*Water for concrete mix and to wash filter sand and gravel
*Miscellaneous tools (e.g. wrench, nuts, bolts)
*Facilities: Workshop space for filter construction
A skilled welder required to fabricate molds. Anyone can be trained to construct and install the filter. Individual householders can assist in constructing their own filters.
Working with cement and heavy molds is potentially hazardous and adequate safety precautions should be used. Concrete filters are heavy and difficult to move and transport.
====Treatment Efficiency====
The outlet should also be cleaned regularly using soap and water or a chlorine solution.
====Manufacturing====
Local production of filters is most common. Molds can be borrowed, rented, bought or constructed locally. Filters can be constructed at a central production facility, or in the community. Filter sand and gravel can be prepared (sieved and washed) on-site or nearby.
Materials and facilities required are:
*Steel mold
*Sand, gravel, and cement
*Filter sand and gravel
*Copper or plastic outlet tubing
*Metal or plastic for the diffuser basin
*5-6 kg of non-galvanized iron nails
*Metal or wood for the lid
*Water for concrete mix and to wash filter sand and gravel
*Miscellaneous tools (e.g. wrench, nuts, bolts)
*Facilities: Workshop space for filter construction
A skilled welder required to fabricate molds. Anyone can be trained to construct and install the filter. Individual householders can assist in constructing their own filters.
Working with cement and heavy molds is potentially hazardous and adequate safety precautions should be used. Concrete filters are heavy and difficult to move and transport.
====Estimated Lifespan====
====Suppliers====
Free mold designs are available from CAWST.
==CostCosts==
{{Treatment_Cost
|CapCost=US$ 12-30
Note: Program, transportation and education costs are not included.
==Country Field experiences== ==Manuals==
==Movies== ==External LinksReference manuals, videos, and links==
*[http://www.cawst.org CAWST (Centre for Affordable Water and Sanitation Technology)]
*[http://www.enpho.org/drinking_water_quality.htm Drinking water quality information from Environment and Public Health Organization (ENPHO)]
This article is based on a factsheet from [http://www.cawst.org/ Centre for Affordable Water and Sanitation Technology (CAWST)], which is gratefully acknowledged.
==References==
* <cite id=Buzunis95>Buzunis, B. (1995). Intermittently Operated Slow Sand Filtration: A New Water Treatment Process. Department of Civil Engineering, University of Calgary, Canada.</cite>
* <cite id=Uy08> Uy, D., Chea, S., Mao, S., Ngai, T. and T. Mahin (2008). Kanchan Arsenic Filter - Evaluation of Applicability to Cambodia - Phase I Technical Report. Cambodian Ministry of Rural Development and the Institute of Technology of Cambodia.</cite>
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