A bacterium in New Jersey's acidic soils could destroy per- and polyfluoroalkyl substances, or PFAs. Delaware's hot spots are southeast of the New Castle airport and west of Dover AFB toward the St. Jones River.
It’s not quite the creature from the black lagoon. But it’s close.
Researchers at Princeton University have discovered that a bacterium found in New Jersey’s acidic soils has the potential to destroy per- and polyfluoroalkyl substances, or PFAs. The toxic, man-made chemicals are the culprits behind an increasing number of drinking water crises across the United States, including widespread contamination in southeast Pennsylvania and at several sites across New Jersey.
One of the biggest problems with PFAs is that the chemicals are built on a carbon-fluorine bond, one of the strongest in chemistry. It makes the chemicals nearly indestructible, with no known natural processes that can completely break them down.
“They have been viewed typically as non-biodegradable,” said Peter Jaffé, a professor of civil and environmental engineering at Princeton.
Enter “acidimicrobium strain A6,” which the less scientifically inclined can just call “A6.” In 2005, Jaffé was studying wetlands in the Assunpink Wildlife Management Area, 12 miles east of Trenton in Upper Freehold, Monmouth County, when he came across the bacterium. It was doing unusual things — living off ammonium and iron — and Jaffé was curious.
“It had some genes for enzymes that looked intriguing,” Jaffé said, as only an environmental scientist could.
By 2018, Jaffé and his team had isolated A6 in the lab and further studied it. The bacterium had qualities similar to microbes that are known to break down other harmful chemicals, such as trichloroethyelene. But what would A6 do to a stronger compound?
“Given the interest in PFAS, we said, ‘Let’s try it,’” Jaffé said.
The results, which Jaffé and research associate Shan Huang published this month in Environmental Science & Technology, are eye-catching. After adding the PFAs chemical perfluorooctanoic acid (PFOA) to hundreds of vials containing A6, and letting them sit for various periods of time, Jaffé observed the bacterium removed as much as 60% of the chemical.
What’s more, his team was able to ascertain that the microbe wasn’t just breaking PFOA down to “smaller” PFAs that still contained the carbon-fluorine bond, which is a concern for other known treatment methods. A6 was actually breaking the bond and creating free-floating fluorides.
They ultimately looked at 20 different kinds of PFAs structures, and found that none escaped A6′s appetite.
“We could see that all of them we could defluorinate,” Jaffé said, stifling a smile. “Which is ... novel.”
But Jaffé admits there is a long way to go between the early promising results and using A6 at the hundreds of sites across the country where PFAs is known to have contaminated drinking water or the environment. The Department of Defense has agreed to fund additional work to figure out exactly how A6 is able to break the bonds, and chemical companies have come calling.
Jaffé also wants to demonstrate that A6 can clear its plate.
“Questions have been raised, can we really get to 100%?” Jaffé said.
There are also questions about ideal conditions. A6 thrives in soils that are acidic and iron rich, common in New Jersey. That’s promising for sites like Joint Base McGuire-Dix-Lakehurst, a site of significant PFAs contamination just 13 miles from Assunpink. A6 has also been found in South Carolina and China.
But environments with karst limestone geology, found in Pennsylvania, are not ideal. Jaffé says they’ll have to tinker: Can they adjust local soil conditions to help A6 thrive in those types of environments? One idea calls for the burying of electrodes to give A6 an extra energy boost in places with low iron, but it’s just a theory.
Perhaps the most practical application would be to create large chambers with ideal A6 living conditions. Then, PFAs could be removed from water with filters. When the filters are washed out, the hyper-concentrated PFAs leftovers could go right into the chamber, as breakfast, lunch and dinner for the microbes.
Or, Jaffé says, the microbes could be put to work eating through leftover sludge from wastewater treatment plants impacted by PFAS.
But, first things first. Jaffé says he’ll begin his DOD-funded work next spring, which will provide access to high-tech equipment to better understand how A6 works.
It may take a while to develop a usable, real-world application. But Jaffé says if it is achieved, early results indicate the microbe from New Jersey has the potential to eat through significant amounts of PFAs in months to a year.
“For what is termed a ‘forever chemical,’ 100 days to one year is fine,” Jaffé said.