Many people in developed countries take clean drinking water for granted. When you turn on a tap, the water has already been filtered, treated with UV light, and disinfected before it reaches your home. However, for hundreds of millions of people in the Global South, this kind of infrastructure is missing.
Researchers at the University of Connecticut and Yale University have developed a new solar-powered water disinfection system that could help solve this problem. Described in the journal npj Clean Water, the system combines several proven disinfection methods into one compact device.
Each method targets different types of pathogens that others might not catch. This system uses only sunlight and a handful of existing techniques to produce safe drinking water nearly year-round.
Many Methods, One Device
Solar pasteurization uses sunlight to heat water to a temperature that kills pathogens, using less than half the energy needed for boiling. Solar disinfection, which involves leaving water in sunlight so UV rays can kill bacteria, can remove 99.9% of bacteria in about six hours on a sunny day. However, viruses are smaller and tougher to kill, sometimes taking up to 30 hours with sunlight alone.
This is where the new system’s innovation comes in. Eric Ryberg, an assistant professor at UConn and the study’s lead researcher, specializes in photosensitizers. These compounds react to sunlight by transferring energy to oxygen molecules in water, making them active enough to neutralize both bacteria and viruses.
“Having multiple ways of disinfecting and treating the water is always better than having one,” Ryberg said. “Those pesky viruses that don’t get inactivated quickly by those technologies — that’s where the photosensitization can really come in.”
A Food Dye as a Safety Indicator
For this system, Ryberg chose a common red food dye, erythrosine, as the photosensitizer. This choice is practical for several reasons. As erythrosine breaks down during disinfection, the water visibly changes color, giving users a clear sign that the water is safe to drink. No extra testing equipment is needed.
Under optimal sunlight, the researchers’ model shows that the system can disinfect water to safe standards in less than an hour, with subsequent batches taking only 28 minutes. Field tests conducted in Guatemala also supported these predictions.
Built to Work Year-Round
One major weakness of solar-based water treatment is its dependence on the weather. Cloudy days and winter can make these systems unreliable, a kind of inconsistency that makes communities hesitant to rely on them.
To solve this, the team tested how the system would work in three cities with very different amounts of sunlight: Cape Town, South Africa, and Sololá, Guatemala, both with significant changes in sunlight between dry and wet seasons, and Phoenix, Arizona, which is sunny almost year-round. In each case, the system provided at least 50 liters of clean water per person per day on all but 20 days of the year.
The study notes that the system can treat more than 70 liters per square meter per day and can supply up to 94% of a household’s hot water needs, helping lower energy costs and improve water security. The device is also made to be scalable. Ryberg sees it being used in individual homes or expanded into larger community systems, depending on local needs.
The Next Step: Going Natural
Ryberg is already exploring options beyond erythrosine. His current work focuses on replacing synthetic photosensitizers with natural alternatives, such as chlorophyll, which gives plants their green color, and hypericin, a compound found in St. John’s Wort. “The ultimate goal is that we can transition to natural things that have a much lower toxicological concern,” he said.
While more testing is needed, the concept is straightforward and scalable. For communities with abundant sunlight but limited access to clean water, this technology could offer a practical solution.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.