Fluorotelomer alcohol biodegradation - Direct evidence that perfluorinated carbon chains breakdown

There is increasing scientific interest to understand the environmental fate of fluorotelomer alcohols (FTOHs) and fluorotelomer-based products which may break down to FTOHs. Both are expected to enter aqueous waste streams, which would be processed in a wastewater treatment plant and therein subject to microbial biodegradation. We investigated the biodegradation of 3-C-14, 1H,1H,2H,2H-perfluorodecanol [CF3(CF2)(6) (CF2CH2CH2OH)-C-14, C-14-8-2 FT0H] in mixed bacterial culture and activated sludge. (CO2)-C-14 and C-14-organic volatiles in the headspace of the sealed bottles and bottles with continuous air flow were analyzed up to 4 months. After sample extraction with acetonitrile, C-14-labeled biotransformation products (metabolites) were quantified by LC/ARC (on-line liquid chromatography/ accurate radioisotope counting) and identified by quadrupole time-of-flight (Q-TOF) mass spectrometry and GC/MSD (mass selective detector). Three metabolites not yet reported in the literature have been identified as CF3(CF2)(6)-(CHOHCH3)-C-14 (7-2 sFTOH), CF3(CF2)(6) (CH)-C-14=CHCOOH (7-3 unsaturated acid or 7-3 u acid), and CF3(CF2)(6) (CH)-C-14=CHCONH2 (7-3 u amide) along with five previously reported metabolites [CF3(CF2)(6) (CF2CH2CHO)-C-14 (8-2 FTAL), CF3(CF2)6-C-14 F2CH2COOH (8-2 acid), CF3(CF2)(6)(CF)-C-14=CHCOOH (8-2 u acid), CF3(CF2)(6) (CH2CH2COOH)-C-14 (7-3 acid), and CF3(CF2)(6) (COOH)-C-14 (PFOA)]. No CF3(CF2)(6) (CF2COOH)-C-14 (C-14-PFNA) was observed, indicating that (x-oxidation does not take place. It was found that strong adsorption to the activated sludge and subsequent transformation, even under continuous air flow, greatly reduced partitioning of 8-2 FTOH or any transformation products to air. CF3(CF2)(4)COOH (PFHA; perfluorohexanoic acid) was observed and increased in mixed bacterial culture over 28 days and accounted for about 1% of the initial C-14-8-2 FTOH concentration from day 28 to day 90. (CO2)-C-14 accounted for 1% of initial C-14 in activated sludge with continuous air flow at day 1 and increased over time. In closed bottles, (CO2)-C-14 in the headspace of activated sludge medium increased to 12% of the available C-14 over 135 days with periodic addition of ethanol, as compared to 3% when no additional ethanol was added. These results show that replenishment of organic carbon enhanced microbial mineralization of multiple -CF2- groups in the fluorocarbon chain of C-14-8-2 FTOH. At day 90 the net increase of fluoride ion in the mixed bacterial culture was 93 mu g L-1, equivalent to 12% of total mineralization (destruction) of the C-14-8-2 FTOH. These results demonstrate that perfluorinated carbon bonds of C-14-8-2 FTOH are defluorinated and mineralized by microorganisms under conditions which may occur in a wastewater treatment plant, forming shorter fluorinated carbon metabolites.