According to EPA, in the United States approximately 34 billion gallons of wastewater are processed every day. At wastewater treatment plants, pollutants are removed including solid suspended particles, organic matter, nitrogen and phosphorous, various pathogens including bacteria, viruses and parasites, as well as chemicals and heavy metals. Once processed, the water is released back into local waterways for various uses such as drinking water, irrigation and sustaining aquatic life. A particular compound which has created great concern is a class of chemicals referred to as PFAS (per- and polyfluorakyl substances), which is \highly resistant to biodegradation. This report first introduces the complexity of the problem in order to set the stage for introducing current and emerging methods for potential PFAS destruction. Efforts have been made to give voice
to the various constituents involved with this challenge including federal, state and local governments, wastewater treatment facilities and industry.
PFAS (per- and polyfluoroalkyl substances) refers to a class of over 12,0001 synthetic chemicals, some of which have been used for decades to enhance a wide range of products. PFAS chemicals have applications in paints, non-stick cookware, stainresistant products, pesticides, fast food packaging, photographic products, dental floss, firefighting foam, and other goods. PFAS are often called “forever chemicals,” as they are highly resistant to biodegradation. Two of the oldest, most common, and widely studied PFAS — PFOS and PFOA — remain of concern, even though they were phased out of production in the U.S. in recent years.
Production and use of other PFAS continues, including newer formulations designed to be safer. While alternatives are being explored, years of PFAS use have led to PFAS accumulation in surface water, groundwater, wastewater, soil, air, and the bodies of fish, deer, and other wildlife. The U.S. Environmental Protection Agency (EPA) has indicated that PFAS can be harmful at the parts per trillion level. As time has gone on, the attention paid to detection, regulation, and remediation of PFAS has shifted from PFOS and PFOA — which drinking water systems were required to test for under the EPA’s third Unregulated Contaminant Monitoring Rule (UCMR 3), issued in 2012 — to a broader array of PFAS found in the environment.
PFAS exist in polymer and non-polymer varieties, the two main non-polymer types being the per- and polyfluoroalkyl substances in the name “PFAS.” Within perfluoroalkyl substances or perfluoroalkyl acids (PFAAs), the two major subgroups are perfluoroalkyl carboxylic acids (PFCAs), or perfluoroalkyl carboxylates, and perfluoroalkane sulfonic
acids (PFSAs), or perfluoroalkane sulfonates. These two groups of PFAS are among the most widely used and studied. PFAAs are often described as long-chain and short-chain PFAS because of their shared behaviors, which influence the associated health effects of exposure, persistence in the environment and the processes that can effectively break them down PFOA and PFOS are both considered long-chain PFAS. The short-chain, long-chain distinction is significant for both PFAS removal and destruction methods.
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