Researchers at the Indian Institute of Technology in Madras have developed a simple point-of-use water filtration technology,using nanomaterials to filter and clean the water, which they say is effective for producing drinking water at a cost of just $US2.50 per year per family.

The device uses a two-stage process to purify the water. In the first stage, it removes biological contaminants, such as bacteria and viruses. In the next stage, silver nanoparticles are used to remove chemical and heavy metal pollutants.

The biggest challenge for the research team was to develop a system that could release silver ions continuously as part of the purification process, without using any electricity. They achieved this by creating a composite structure that traps the nanoparticles in "composite cages" made from a clay-like material This allows the device to produce water of drinking standards at a rate of up to 10 litres per hour.