Spongy Filter Produces Purified Lake Water When Placed In the Sun, Shows A New Study

May, 2021 - by CMI


A modern technology which utilizes sunlight to power water treatment could help solve the issue of supplying safe drinking water in remote areas.

Although these systems are successful, they could take a long time to generate enough drinkable water. In pursuit of a faster-acting solution, Princeton University scientists created a low-cost flat sponge-like system that absorbs water from a lake or pond and then releases filtered water when exposed to sunlight. Implementing a solar still is one of the most popular uses of the sun to purify water. Although, there are several types of heat stills, they all work by capturing pure condensed water vapor which evaporates from polluted liquid water since it is exposed to the sun.

The gel mesh stays loose and free after the device is left to float in relatively cold water. Water is attracted to hydrophilic molecules inside the gel by pores in the two outer layers. Pollutants and pathogens cannot move through the pores of alginate. Whenever the filter is taken out of the water and exposed to sunshine, the dark polydopamine increases solar gain, allowing it to heat up. Hydrophobic molecules in the gel are pulled together as a result. The gel contracts as a result, effectively wringing the filtered water from the spongy stuff. The filtered water is stored in a tub under the filter.

"The most interesting aspect of this work to me is that it will run fully off-grid on both large and small scales," Priestley said. "It may also be used in developing countries where low-cost, non-powered water purification is needed."

The system was first tested for an hour in around 77°F water of Lake Carnegie on the Princeton campus. It was then taken outside and put in the sun for another hour, during which time it heated over 91°F and released the water it had absorbed. Toxins and bacteria, as well as potentially dangerous microbes present in the lake, were found to be absent from the water.