Key points:
- Researchers developed a new method to collect water from fog and purify it at the same time.
- Specially selected polymers in a close-mesh lattice ensure efficient droplet collection, while titanium dioxide in the lattice breaks down pollutant molecules.
- Water recovery from fog and steam may help alleviate water scarcity.
People living in dry but foggy areas often hang up nets to collect water droplets for drinking, cooking and washing. One major issue with these fog nets is that atmospheric pollution and its hazardous substances end up in the water droplets. As a result, the collected water cannot be safely used without being treated.
Researchers at ETH Zurich developed a new method that simultaneously collects and purifies water from fog. Their method, published in Nature Sustainability, uses a metal wire close-mesh lattice coated with polymers and titanium dioxide. The polymers ensure the water droplets collect efficiently on the mesh, while titanium dioxide acts as a chemical catalyst to break down molecules from organic pollutants.
“Our system not only harvests fog but also treats the harvested water, meaning it can be used in areas with atmospheric pollution, such as densely populated urban centers," said Ritwick Gosh, one of the study’s authors.
After installation, the technology requires almost no maintenance or energy. A small dose of UV regenerates the titanium oxide catalyst—half an hour of sunlight for 24 hours of reactivation. Once reactivated, the catalyst remains active for a long time in the dark, which is crucial as many foggy areas have rare periods of sunlight.
The fog collector was tested both in the lab and a small pilot plant in Zurich. The team collected 8% of the water in artificially created fog and broke down 94% of the added organic compounds including diesel droplets and bisphenol A.
Fog and steam are an underutilized water source that could be used to help alleviate the scarcity of water. This new technology, developed for fog, could be used to recover water from cooling towers.
“In the United States, we use a great deal of fresh water to cool power plants,” said Thomas Schutzius, professor at University of California, Berkeley. “It would make sense to capture some of this water before it escapes and ensure that it is pure in case you want to return it back to the environment.”