UC Berkeley researchers have developed a method of collecting and purifying water from fog, offering an alternative water source.

Microscopic droplets of water can be harvested from fog as it passes through a mesh, which is coated with particles that degrade pollutants in the water, said Thomas Schutzius, assistant professor of mechanical engineering on campus and principal investigator of the study.

“We were interested in seeing if we could come up with a way to not just harvest the water but also … do some type of a purification step where we will remove important contaminants, like organic contaminants that are naturally in the air and near your cities,” Schutzius said.

Fog harvesting is already used in regions such as South America, but the dual purpose of the mesh to both collect and purify water is a new development, according to Schutzius. According to a press release from Berkeley Engineering, previous research on harvesting water from fog using “nanoscopic woven mesh” used uncontaminated fog.

Fog droplets can contain potentially cancerous organic pollutants if collected in urban areas and even downwind areas, making collected water unsafe to drink, the press release noted.

The coating on the mesh is made of titanium dioxide nanoparticles that have photocatalytic properties, Schutzius said. They thus become reactive when in contact with ultraviolet light, which, when shone on the particles, embed onto the water-collecting mesh and degrade contaminants in the water.The coatings required active ultraviolet lamp illumination to complete the purification, which impeded the treatment of organic pollutants, the press release added.

“When you have fog, it’s not really sunny — the point is that you would want the coating to maintain this property or some reactivity after it becomes cloudy and foggy when you would do the harvesting and purification step,” Schutzius said. “Those nano-particles in there allow you to do that.”

This purification and harvesting method was developed to address the “pressing” problems of climate change and water scarcity, according to Schutzius. He noted the next step in this research would be outreach to foundations and organizations who could potentially adopt the new technology.

Benefits of the technology include its easy maintenance, and will especially benefit people living in dry, foggy areas, according to a press release from ETH Zurich.

Schutzius and the rest of the team, which includes Ritwick Ghosh, lead author of the paper, and researchers at the Max Planck Institute for Polymer Research in Germany, among others, have conducted outdoor tests with the mesh.

“It’s clear to us that we’re going to have to start dealing with the pollution problem as well our purification problem within these technologies if we’re going to get wider adoption of them for fog,” Schutzius said. “As a concept it has quite some potential as people started to look to the atmosphere to collect more water.”