Forever chemicals are incredibly stable molecular compounds — famously so, in the case of Teflon, which withstands very high temperatures during cooking. It makes destroying PFAS a major logistical problem.
But one compound may be the solution to that problem: H2O, or regular old water. Duke Professor Marc Deshusses co-founded a company called 374Water, which aims to use a tried and tested method to destroy PFAS and other contaminants at commercially viable volumes, using supercritical water.
“Most people think of water as being either a liquid or a solid or vapor," Deshusses explained. "But there's actually a fourth state of water, which is called supercritical. And you get it at a higher temperature and pressure.”
Water in that state becomes a cross between a gas and a liquid, and when air is injected, it leads to oxidative reactions. The powerful carbon bonds that make PFAS so stable are broken, leaving just the smaller components.
"What comes out is clean water that can be reused," Deshusses said. "And there's mineral salts because of the salts that are in the waste to start with. And those can be sieved or separated by gravity, and then be re-used or disposed of.”
The technology would be an important advancement to dealing with the ubiquitous PFAS contamination around the globe, as even PFAS filters simply concentrate the forever chemicals, rather than destroying them. The granular activated carbon used by CFPUA, for example, goes through a process called "thermal regeneration," where the carbon is burned to remove contaminants. But that process has problems, according to Deshusses. "It's in that process they claim that the PFAS are destroyed," he said, but "I've yet to see the scientific papers that will provide evidence that they're not releasing massive amounts of volatile species and gases containing smaller molecules and in fluorine."
Deshusses said European countries are actually using this technology to recover phosphorus from sewage, and the company hopes to place a unit on farms across the US that raise livestock for slaughter.
While one of the outputs of this process is a small amount of CO2, it’s actually a very energy-efficient process because the chemical reactions generate their own energy.
“These units can run just on the energy that is embedded in the waste, it can run on its own,” he said.
While only a few commercially-sized units have been created and shipped so far, Deshusses said they could be used at chemical plants, wastewater treatment facilities, and even farms to address potentially harmful waste — including PFAS. And future systems will be able to treat up to 30 tons of waste per day, and fits inside 3 standard shipping containers.
Below is a video demonstrating the use of the technology on Duke University's campus.
