6:2 and 8:2 Fluorotelomer Alcohol Anaerobic Biotransformation in Digester Sludge from a WWTP under Methanogenic Conditions
2013
Zhang, Shu | Szostek, Bogdan | McCausland, Patricia K. | Wolstenholme, Barry W. | Lu, Xiaoxia | Wang, Ning | Buck, Robert C.
6:2 FTOH and 8:2 FTOH [FTOHs, F(CF₂)ₙCH₂CH₂OH, n = 6, 8] are the principal polyfluorinated raw materials used to manufacture FTOH-based products, which may be released to WWTPs during their product life cycle. For the first time, anaerobic biotransformation of FTOHs and key biotransformation intermediates in WWTP digester sludge under methanogenic conditions was investigated. 6:2 FTOH was transformed to 6:2 FTCA, [F(CF₂)₆CH₂COOH, 32–43 mol %], 6:2 FTUCA [F(CF₂)₅CF═CHCOOH, 1.8–8.0 mol %], and 5:3 acid [F(CF₂)₅CH₂CH₂COOH, 18–23 mol %] by day 90 and day 176 in two separate studies. 8:2 FTOH was transformed by day 181 to 8:2 FTCA (18 mol %), 8:2 FTUCA (5.1 mol %), and 7:3 acid (27 mol %). 6:2 and 8:2 FTOH anaerobic biotransformation led to low levels of perfluorohexanoic acid (PFHxA, ≤0.4 mol %) and perfluorooctanoic acid (PFOA, 0.3 mol %), respectively. 6:2 FTUCA anaerobic biotransformation led to a newly identified novel transient intermediate 3-fluoro 5:3 acid [F(CF₂)₅CFHCH₂COOH] and 5:3 acid, but not 5:2 sFTOH [F(CF₂)₅CH(OH)CH₃] and α–OH 5:3 acid [F(CF₂)₅CH₂CH(OH)COOH], two precursors leading to PFPeA (perfluoropentanoic acid) and PFHxA. Thus, FTOH anaerobic biotransformation pathways operated by microbes in the environment was likely inefficient at shortening carbon chains of FTOHs to form PFCAs (perfluorinated carboxylic acids). These results imply that anaerobic biotransformation of FTOH-based products may produce polyfluorinated acids, but is not likely a major source of PFCAs detected in anaerobic environmental matrices such as anaerobic digester sludge, landfill leachate, and anaerobic sediment under methanogenic conditions.
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