The need for remediation of poly‐ and perfluoroalkyl substances (PFASs) is growing as a result of more regulatory attention to this new class of contaminants with diminishing water quality standards being promulgated, commonly in the parts per trillion range. PFASs comprise >3,000 individual compounds, but the focus of analyses and regulations has generally been PFASs termed perfluoroalkyl acids (PFAAs), which are all extremely persistent, can be highly mobile, and are increasingly being reported to bioaccumulate, with understanding of their toxicology evolving. However, there are thousands of polyfluorinated “PFAA precursors”, which can transform in the environment and in higher organisms to create PFAAs as persistent daughter products. Some PFASs can travel miles from their point of release, as they are mobile and persistent, potentially creating large plumes. The use of a conceptual site model (CSM) to define risks posed by specific PFASs to potential receptors is considered essential. Granular activated carbon (GAC) is commonly used as part of interim remedial measures to treat PFASs present in water. Many alternative treatment technologies are being adapted for PFASs or ingenious solutions developed. The diversity of PFASs commonly associated with use of multiple PFASs in commercial products is not commonly assessed. Remedial technologies, which are adsorptive or destructive, are considered for both soils and waters with challenges to their commercial application outlined. Biological approaches to treat PFASs report biotransformation which creates persistent PFAAs, no PFASs can biodegrade. Water treatment technologies applied ex situ could be used in a treatment train approach, for example, to concentrate PFASs and then destroy them on‐site. Dynamic groundwater recirculation can greatly enhance contaminant mass removal via groundwater pumping. This review of technologies for remediation of PFASs describes that: GAC may be effective for removal of long‐chain PFAAs, but does not perform well on short‐chain PFAAs and its use for removal of precursors is reported to be less effective; Anion‐exchange resins can remove a wider array of long‐ and short‐chain PFAAs, but struggle to treat the shortest chain PFAAs and removal of most PFAA precursors has not been evaluated; Ozofractionation has been applied for PFASs at full scale and shown to be effective for removal of total PFASs; Chemical oxidation has been demonstrated to be potentially applicable for some PFAAs, but when applied in situ there is concern over the formation of shorter chain PFAAs and ongoing rebound from sorbed precursors; Electrochemical oxidation is evolving as a destructive technology for many PFASs, but can create undesirable by‐products such as perchlorate and bromate; Sonolysis has been demonstrated as a potential destructive technology in the laboratory but there are significant challenges when considering scale up; Soils stabilization approaches are evolving and have been used at full scale but performance need to be assessed usin...

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We isolated an acid-tolerant sulfate-reducing bacterium, GB-SRB4.2, from coal mine-derived acidic mine drainage (AMD)-derived sediments. Sequence analysis of partial 16S rRNA gene of GBSRB4.2 revealed that it was affiliated with the genus Desulfosporosinus. GBSRB4.2 reduced sulfate, Fe(III) (hydr)oxide, Mn(IV) oxide, and U(VI) in acidic solutions (pH 4.2). Sulfate, Fe(III), and Mn(IV) but not U(VI) bioreduction led to an increase in the pH of acidic solutions and concurrent hydrolysis and precipitation of dissolved Al 3+ . Reduction of Fe(III), Mn(IV), and U(VI) in sulfate-free solutions revealed that these metals are enzymatically reduced by GBSRB4.2. GBSRB4.2 reduced U(VI) in groundwater from a radionuclide-contaminated aquifer more rapidly at pH 4.4 than at pH 7.1, possibly due to the formation of poorly bioreducible Ca-U(VI)-CO 3 complexes in the pH 7.1 groundwater.

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As a follow-up to the PFAS Experts Symposium 2 held on June 30 and July 1, 2021, the In situ Remediation Technologies Committee prepared a technical and regulatory review of in situ technologies that are potentially applicable to sites with per-and polyfluoroalkyl substances (PFAS) contamination. The technologies included in the review were limited to those that are deemed commercially available and potentially applicable to sites with soil, groundwater, surface water, and sediment contamination. While the scope of commercially available in situ remediation technologies for PFAS remains limited, some in situ adsorption technologies, most notably activated carbon-based technologies, can be considered fully commercialized. Though questions remain regarding the long-term effectiveness of these technologies, field applications deployed for at least a half-decade or more continue to demonstrate effectiveness. | INTRODUCTIONThis paper was developed from presentations given at the PFAS Experts Symposium 2 (Symposium), a virtual, invitation-only conference held on June 30 and July 1, 2021. A previous PFAS Experts Symposium was held in May 2019. A primary objective of the Symposium was to share current information on per-and polyfluoroalkyl substances (PFAS) among experts in different scientific and technical fields. All listed authors participated in the Symposium and contributed to the discussions and presentations on available in situ remediation technologies to treat PFAS contamination in various environmental media.The Committee on "Available In Situ Remediation Technologies" was charged with benchmarking a key subset of remediation technologies. The concept of "in situ" technologies is widely understood to include technologies that provide treatment or containment within the subsurface. Further, "available" was defined by the Committee as technologies that have advanced beyond the research stage and are available for use either now or in the near future.