More than 70 years ago, a group of chemicals known as PFAS promised to make people’s lives easier and more efficient. The category of chemicals — whose full name is per- and polyfluoroalkyl substances — was developed in the 1940s to resist heat, grease, stains, and water. That made them ideal coatings for food packaging, paper plates, and cookware.
They were also used as firefighting foam for military training exercises and emergency responses starting in the 1970s.
But since then, scientists have uncovered links between PFAS and cancer, liver damage, thyroid disease, and developmental issues.
PFAS can linger in water and air for thousands of years, so consuming or inhaling them means they could stay in the body for life — hence their nickname, “forever chemicals.”
But a group of researchers at Clarkson University in New York is developing a way to destroy PFAS in water. Together with the US Air Force, the team is using machines called plasma reactors to sever the chemicals’ carbon-fluorine bonds — the same bonds that make them virtually indestructible in the environment.
The technology applies only to PFAS in groundwater. (The researchers are working on a separate project to remove PFAS from soil.) But it could eventually be cheaper than the current water-filtration process.
Scientists are splitting PFAS molecules apart
The Air Force began using a new firefighting foam that doesn’t contain PFAS in July 2018, but it still has to contend with the legacy of the old one. The chemicals have gotten into the groundwater at numerous Air Force bases across the US, forcing the military to spend more than $2.2 billion to clean up PFAS-contaminated sites, according to a report on the Environmental Protection Agency’s website.
That’s why the Air Force is looking for a cheaper way to clean contaminated water.
To test their technology, the Clarkson researchers built a 20-foot-long mobile trailer that holds two plasma reactors. For two weeks in September, they pumped PFAS-contaminated groundwater from the Wright-Patterson Air Force Base in Ohio into the reactors.
Argon gas at the bottom of the reactors carries the PFAS molecules to the surface. The researchers then use high-voltage electrodes to generate plasma, an ionized gas made of free-roaming electrons and positive ions.
The plasma zaps the water’s surface, where it spreads across like fire, hitting the PFAS molecules and splitting them apart. Once the carbon and fluorine molecules have been separated, the PFAS compound is effectively destroyed.
Selma Mededovic, the principal researcher overseeing the project, said treating a single gallon of water this way takes one minute.
That’s far slower than one of the standard methods for removing PFAS: adding carbon to contaminated water. With that approach, the chemicals stick to carbon, allowing clean water to be filtered out. Hundreds of gallons of water per minute can be treated this way, but Mededovic said the spent carbon needed to be incinerated afterward.
That incineration process costs about $3 to $4 per gallon of contaminated water, she said. Her plasma method, by contrast, is at least 40% cheaper (though the estimate does not include the cost of the reactors).
Mededovic said she would have a better sense of how much the reactors cost once the first commercial prototype is built. She expects it to be operational by the end of this year.
In the meantime, her team is ramping up the technology to treat 15 gallons of contaminated water per minute. Eventually, they hope to treat about 200 gallons per minute.
“We are working on scaling up our process to be competitive to carbon,” Mededovic said.
The EPA doesn’t have a legal limit for PFAS in water
The Clarkson team’s plasma reactor reduces PFAS concentrations in water well below the EPA’s general limit for drinking-water contaminants: 70 parts per trillion.
But environmental groups have expressed concern that the limit is too high when it comes to PFAS. (The nonprofit Environmental Working Group endorses a limit of one part per trillion).
The EPA pledged to develop national drinking-water regulations for PFAS by the end of 2019, but the deadline came and went.
On Friday, the US House of Representatives passed a group of measures that would require the EPA to set that guideline. The measures would also label PFAS as “hazardous substances,” which would allow the EPA to require industrial manufacturers to clean them up.
The Trump administration has threatened to veto the measures, however, calling them “problematic and unreasonable” and a “litigation risk.”
But Mededovic said even scientific innovations like hers weren’t enough without regulations.
“Elevated levels of PFAS have been found in many public and private water sources, and we need to regulate these compounds,” she said. “Companies need to be accountable for what they’re producing and releasing.”