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There has been substantial research into different technologies for arsenic removal, which the Practical Action paper that Binaya has provided covers very comprehensively. I carried out some research on different technologies a couple of years ago and one of the most practical household systems I came across was the Kanchan Arsenic Filter or KAF. A paper reporting the results from field tests on the KAF in Cambodia is here: https://web.mit.edu/watsan/Docs/Other%20Documents/KAF/Cambodia%20KAF%20Phase%20I%20Technical%20Report%20FINAL%20Sep08.pdf

The most common household technologies for arsenic and iron removal use filtration/sedimentation techniques of their insoluble compounds. A word of caution, therefore, needs to be given as at some point the waste products from the filters must be disposed of. It is imperative that thought is given to where a suitable disposal site is located which should not be close to an area that could further contaminate the groundwater. The subsurface aerated water injection process gets around this problem by oxidising the arsenic to an insoluble form within the borehole, so leaving it behind when the water is extracted. But this technology is perhaps more community based than household.

One of the greatest challenges of arsenic removal at household level is also ensuring that the technology is indeed working. There are no simple indicators, such as colour, smell or even taste, to show that the arsenic has been removed and using any handheld technologies is too expensive for day to day use. This is perhaps the next big challenge for research.