Biotransformation of 6:2 fluorotelomer sulfonate and microbial community dynamics in water-saturated one-dimensional flow-through columns

• Published in: Water research (Oxford) 2024-03, Vol.252, p.121146-121146, Article 121146
• Main Authors: Yan, Peng-Fei, Dong, Sheng, Woodcock, Matthew J., Manz, Katherine E., Garza-Rubalcava, Uriel, Abriola, Linda M., Pennell, Kurt D., Cápiro, Natalie L.
• Format: Article
• Language: English
• Subjects: 6:2 FTS; AFFF; Biotransformation; Fluorotelomer sulfonate; Groundwater contaminant transport; Mathematical modeling; Microbial community; PFAS
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2024.121146

•PFAS biotransformation was investigated in water-saturated flow-through columns.•Longer residence time and flow interruptions enhanced 6:2 FTS biotransformation.•Biotransformation rates during the column experiments were mathematically modelled.•Planktonic microbial communities in the columns remained relatively stable.•Porous media attached microbial community composition shifted along the flow path. Nearly all per- and polyfluoroalkyl substances (PFAS) biotransformation studies reported to date have been limited to laboratory-scale batch reactors. The fate and transport of PFAS in systems that more closely represent field conditions, i.e., in saturated porous media under flowing conditions, remain largely unexplored. This study investigated the biotransformation of 6:2 fluorotelomer sulfonate (6:2 FTS), a representative PFAS of widespread environmental occurrence, in one-dimensional water-saturated flow-through columns packed with soil obtained from a PFAS-contaminated site. The 305-day column experiments demonstrated that 6:2 FTS biotransformation was rate-limited, where a decrease in pore-water velocity from 3.7 to 2.4 cm/day, resulted in a 21.7–26.1 % decrease in effluent concentrations of 6:2 FTS and higher yields (1.0–1.4 mol% vs. 0.3 mol%) of late-stage biotransformation products (C4C7 perfluoroalkyl carboxylates). Flow interruptions (2 and 7 days) were found to enhance 6:2 FTS biotransformation during the 6–7 pore volumes following flow resumption. Model-fitted 6:2 FTS column biotransformation rates (0.039–0.041 cmw3/gs/d) were ∼3.5 times smaller than those observed in microcosms (0.137 cmw3/gs/d). Additionally, during column experiments, planktonic microbial communities remained relatively stable, whereas the composition of the attached microbial communities shifted along the flow path, which may have been attributed to oxygen availability and the toxicity of 6:2 FTS and associated biotransformation products. Genus Pseudomonas dominated in planktonic microbial communities, while in the attached microbial communities, Rhodococcus decreased and Pelotomaculum increased along the flow path, suggesting their potential involvement in early- and late-stage 6:2 FTS biotransformation, respectively. Overall, this study highlights the importance of incorporating realistic environmental conditions into experimental systems to obtain a more representative assessment of in-situ PFAS biotransformation. [Display omitted]