A SIMPLE DEVICE FOR DISINFECTING WATER WITH SUNSHINE


mage credit: HELIOZ


An easy-to-use measuring device indicates when contaminated water has been sufficiently exposed to the sun’s UV rays for water-borne pathogens to be eliminated

Around the world, 1.8 billion people lack access to safe drinking water. To avoid water-borne disease, these people must treat the water available to them before they can drink it.

A popular method is to boil the water. However, this and other methods cause carbon emissions and air pollution. They also lead to cost.

Sunlight is a good method to disinfect the water. The difficulty is knowing when contaminated water has been exposed for a sufficient length of time for the UV rays to have rendered it safe. Solar water disinfection (SODIS) is a process where the sun’s natural UV rays eliminate pathogens—such as bacteria, viruses, and protazoa—from contaminated water exposed to sunshine.

Austrian social enterprise HELIOZ has developed the WADI – a World Health Organization approved device that visualises the process of SODIS in water containers such as plastic and glass bottles. The WADI device, which can measure UV light, is placed alongside bottles of contaminated water exposed to sunshine, so that it receives the same dosage of UV rays. It can then be used to measure when the bottles have received sufficient exposure to render them safe – defined as the removal of 99.99 per cent of pathogens. This is done using reference values stored in the device.

The device is easy-to-use and designed for water treatment at the household level. Device users can look at a progress bar to track the rate of disinfection, and when the process is finished, the device displays a smiley face.

HELIOZ used the WADI devices as part of a campaign launched to coincide with World Water Day 2021. The campaign was focused on communities in India, Africa, and Southeast Asia. These communities received WADI devices, as well as water, sanitation, and hygiene (WASH) training. The results of the project were impressive: in the project areas, the rate of water-borne disease was reduced by 80 per cent.

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