Purifying drinking water by putting it in plastic bottles on the roof in the sun sounds simple. But unless people understand how the process works and know when the water is ready to drink, they stay thirsty.
A Mercy Corps project in Tajikistan, funded by Xylem Watermark’s Disaster Risk Reduction Water Initiative, is using solar disinfection (called "SODIS") to bring cheap, safe drinking water to 30,000 people in rural areas.
But the $130,000 project has its holes: the process of waiting six hours for the water to be disinfected by the sun seems so simple that some people aren’t sure it works. They feel like they need a more concrete way to know when they can drink their water, says Mercy Corps disaster risk reduction specialist Anne Castleton.
According to Castleton, “Right now, no visual litmus test exists to let them know when the water is safe to drink.”
Here’s how the technology works: families place unpurified water in bottles, then place them in direct sunlight on the roofs of their home for six hours of good sunlight. According to SODIS, an initiative of Eawag, the Swiss Federal Institute of Aquatic Sciences and Technology, “The UV-A rays in sunlight kill germs such as viruses, bacteria and parasites (giardia and cryptosporidia). The method is very simple and its application is safe. It is particularly suitable for treating relatively small quantities of drinking water.”
Currently, people have to pay close attention to when the water is ready to drink and when they need to switch out old bottles for new ones. This is time-consuming and energy-intensive in communities where public confidence in this water treatment method is tepid at best, according to Mercy Corps.
In a country with 300 annual days of sun but where 56 percent of the population lacks access to clean drinking water, SODIS technology holds a lot of promise, explains Ramesh Singh of Mercy Corps Tajikistan.
But as Castleton points out, maximizing the potential benefits is hard. “Successfully incorporating SODIS technology into communities requires behavior changes and active engagement of the people who live there,” she says.
SODIS technology works, but it has never come to scale. It seems too simple to people.
Scaling-up the reach of SODIS technology requires a two-pronged approach. Mercy Corps and Xylem Watermark are already focused on the first part: increasing knowledge and raising confidence in the SODIS method. But a cheap, simple litmus test--something that shows a "green light" when the water's ready, for example--that people can self-administer is the missing prong.
If and when that becomes available, safe and affordable sun-soaked drinking water will be on the roofs and in the homes of thirsty communities in Tajikistan and beyond.
Watch and listen as Ramesh Singh of Mercy Corps Tajikistan describes solar solutions for water access.