The Sono arsenic filter was invented in 2006 by Abul Hussam, who is a chemistry professor at George Mason University (GMU) in Fairfax, Virginia.
Farmers had been drinking fresh groundwater from wells, whereas previously they had had to use ponds and mudholes which were contaminated with bacteria and viruses.
However, these wells were also contaminated with naturally occurring high concentrations of poisonous arsenic, causing skin ailments and cancers.
Allan Smith, an epidemiologist at the University of California at Berkeley, observed that the arsenic problem affects millions of people worldwide: You can't see it or taste or smell it.
The final version contains 20 pounds (9 kg) of shards of porous iron, which bonds chemically with arsenic.