Biological cleaning was invented for certain “forever chemicals.”

University of California, Riverside chemical and environmental engineering scientists have identified two species of bacteria found in soil that break down a stubborn class of “forever chemicals,” offering hope for low-cost biological cleanup of industrial pollutants.

These bacteria destroy a subgroup of per- and poly-fluoroalkyl substances, or PFAS, that have one or more chlorine atoms in their chemical structure, Yujie Men, assistant professor in the Bourns College of Engineering, and his UCR colleagues, report in the journal Natural Water.

Unhealthy chemicals linger in the environment for decades or longer because of the extraordinarily strong carbon-to-fluorine bonds. Amazingly, the UCR team found that the bacteria cleaved the pollutant’s chlorine-carbon bond, which started a series of reactions that destroyed the chemical structure forever, rendering it harmless.

“What we found is that the bacteria can do the breaking of the carbon-chlorine bond first, resulting in an unstable intermediate,” Men said. “And then that unstable intermediate undergoes spontaneous defluorination, which is the breaking of the carbon-fluorine bond.”

Chlorinated PFAS are a large group in the forever chemical family of thousands of compounds. They include a variety of non-flammable hydraulic fluids used in industry and compounds used to make chemically stable films that serve as moisture barriers in a variety of industrial, packaging, and electronics applications.

Two species of bacteria – Desulfovibrio aminophilus and Sporomusa sphaeroides – identified by the Men’s group as naturally occurring and known to live in underground microbiomes where groundwater may be contaminated with PFAS. For accelerated cleanup, inexpensive nutrients, such as methanol, can be injected into groundwater to promote bacterial growth. This will greatly increase the presence of bacteria to destroy pollutants more effectively, said Men. If bacteria are not present, contaminated water can be inoculated with one of the bacterial species.

The title of this paper is “Substantial defluorination of polychlorofluorocarboxylic acids induced by anaerobic microbial hydrolytic chlorination.” Men is the corresponding author and Bosen Jin, a UCR chemical and environmental engineering graduate student, is the lead author. Another UCR co-author is postdoc Jinyu Gao; former postdoc Huaqing Liu; former graduate students Shun Che and Yaochun Yu; and Associate Professor Jinyong Liu.

The study expands on previous work by Men, in which he showed that microbes could break down a class of stubborn PFAS called fluorinated carboxylic acids.

Microbes have long been used for biological cleaning of oil spills and other industrial pollutants, including the industrial solvent trichlorethylene or TCE, which Men has studied.

But what is known about using microorganisms to clean PFAS is still in its infancy, Men said. The findings are very promising because biological treatments, if effective pollutant-eating microbes are available, are generally cheaper and more environmentally friendly than chemical treatments. Pollutant-eating microbes can also be injected into hard-to-reach locations underground.

The latest men’s PFAS study comes as the US Environmental Protection Agency announces new regulations to spur clean-up of PFAS-contaminated groundwater sites across the nation because the chemical has been linked to a number of adverse health effects, including cancer, kidney disease and hormone disruption. .

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