In a village called Aam-bagan in Nagaon district of Assam, Sumitra Biswas summoned her grandson to help her pour water into the filter kept in the courtyard of their house. The filter -- three buckets, fitted with taps, at three different levels -- was set up by the family itself through a simple, DIY (do-it-yourself) method. Over the next one hour when the water was allowed to stand before being collected for safe consumption, this seemingly simple filter removed arsenic (and also iron) -- a grave problem in Assam because of its devastating effects, including causing cancer.

Arsenic contamination of groundwater in Assam is a serious issue. According to data presented by the Public Health Engineering Minister Rihon Daimary to the state assembly in October 2018, groundwater in 6,881 areas in 24 districts (of the total 33) of the state is contaminated with arsenic. This has grave implications. Long-term consumption of groundwater arsenic can lead to chronic poisoning, thereby causing diseases like cancer, bronchitis, diabetes, bone marrow depression and cardiovascular diseases.