Many people get clean water easily from a tap, but millions still struggle to find safe drinking water every day.
Now, scientists are using sunlight in simple ways to make water safe, even in places without modern systems.
Unsafe drinking water remains a serious issue worldwide. The World Health Organization warns that contaminated water spreads diseases like cholera, typhoid, and diarrhea.
Around 1.7 billion people still rely on unsafe water sources. Children face the greatest risk. Every year, hundreds of thousands of children die from water-related diseases.
At the same time, many families live in areas without proper water systems. This makes safe water a daily challenge, especially in low-income communities.
Why current solutions fall short
Many households use simple methods to clean water. Boiling is the most common one. It works well, but it needs fuel like wood or electricity. This creates a burden for families who already struggle with resources.
Other methods include filters and solar disinfection. Filters remove large particles, but tiny viruses can still pass through. Solar disinfection uses sunlight, but it often takes too long.
In some cases, it can take more than a full day to make water safe. Because of these limits, many systems fail to provide enough clean water every day.
A new solar-powered solution
Researchers from Yale University and other institutions developed a new system, the Solar Enclosure for Water Reuse (SEWR). This system combines multiple methods into one design.
Instead of relying on just one technique, the system uses sunlight in different ways at the same time. It combines solar disinfection, solar heating, and photosensitization. This approach improves both speed and effectiveness.
“Many hands make light work in drinking water disinfection,” noted Eric Ryberg, co-author of the study. “It really allows us to check a lot of boxes and provide water quality that allows people to feel dignified, no matter what resources they might have available to them.”
How sunlight cleans water
Sunlight helps clean water in several ways. One method uses UV rays to damage bacteria and viruses. Another method heats water to kill harmful organisms.
“The UVA radiation will interact with compounds in the water or in the organisms themselves to generate oxidative stress to inactivate the organism,” said Ryberg.
“Or UVB radiation, the one that’s responsible for our sunburns, will actually induce DNA damage in the organisms themselves.”
But sunlight alone is not always enough. Viruses are harder to kill and need longer exposure.
The power of combining methods
The new system solves this problem by combining multiple techniques. This is called a multi-barrier approach. Each method targets different types of germs.
“Having multiple ways of disinfecting and treating the water is always better than having one, because while that prefiltration step is really effective for removing large organisms, like protozoa or worms, some smaller bacteria will slip through the filter,” said Ryberg.
“Having technologies like pasteurization or solar disinfection are quite effective against bacteria. But those pesky viruses that don’t get inactivated quickly by those technologies, that’s where the photosensitization can really come in.”
This combined approach makes the system much more reliable, even in changing weather.
Faster and more reliable results
One of the biggest advantages of this system is speed. Traditional solar methods can take up to 30 hours to kill viruses. This new system can do the same job in less than an hour under good sunlight.
Even in cloudy conditions, the system still works. It can clean water within a few hours, which is much faster than older methods. This makes it more practical for daily use.
The system also produces enough water for daily needs. Studies show it can meet the minimum water requirement set by the United Nations for households across different climates.
Designed for real-life use
Unlike many devices, this system fits into buildings. It can be built into roofs or walls, so it does not take extra space. It collects sunlight during the day and uses it to clean and heat water.
This design also reduces energy costs. The system can provide hot water for most of the year. In some places, it can supply hot water for over 80 to 90 percent of the year. This means families can save money and use less fuel.
“It might make sense for a community to have a system like this be built up into a larger scale, and have it serve the entire community,” Ryberg said. “Or It might make sense to have it be on the relatively small scale and serving individual households.”
The system also includes a clever feature. It uses a dye that changes color when the water becomes safe. This gives a clear visual signal.
Many older methods do not provide this feedback. People often guess if the water is safe. This new feature builds trust and makes the process easier to follow.
Moving toward natural solutions
Right now, the system uses a food-safe dye called erythrosine. Researchers are working to replace it with natural compounds from plants. These include chlorophyll and substances found in herbs.
“The ultimate goal is that we can transition to natural things that have a much lower toxicological concerns,” Ryberg said.
This change could make the system even safer and more sustainable.
Clean water for all
This solar system shows how simple ideas can create powerful solutions. By using sunlight in smarter ways, it becomes possible to provide safe water even in areas without infrastructure.
The system combines science, design, and nature. It reduces disease risk, lowers energy costs, and improves daily life.
With further development, the Solar Enclosure for Water Reuse could bring clean water to millions of people who need it most.
The study is published in the journal npj Clean Water.
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