Biodegradation of 6-2 fluorotelomer alcohol in activated sludge
6-2氟调醇在活性污泥中的降解

Aerobic biotransformation of 6-2 fluorotelomer alcohol (6-2 FTOH, F(CF2)6CH2CH2OH) was studied in a closed bottle system with activated sludge for the first time. The concentrations of 6-2 FTOH and metabolites were determined during the test period (28 days) and biodegradation rates at each sampling time were calculated. The target compounds were not only measured in activated sludge and water phase, but also in headspace and septa because the parent compound and some metabolites are highly volatile. The results indicated that 6-2 FTOH was ready to degrade in activated sludge, and the half-time of 6-2 FTOH was 0.9 day. Large quantity of 6-2 fluorotelomer carboxylic acid (6-2 FTCA) and 6-2 fluorotelomer unsaturated carboxylic acid (6-2 FTUCA) were produced at the beginning of experiment, and their molar yields were 25.4% and 10.8% at 24 h, respectively. Along with the degradation, 6-2 FTCA and 6-2 FTUCA were further transformed to other metabolites with the final molar yields of 0% and 1.2%, respectively. 5-3 polyfluorinated acid (5-3 FTCA) and 5-2 secondary fluorotelomer alcohol (5-2s FTOH) were the primary metabolites at 28 d and their molar yields were 23.4% and 17.6%, respectively. The final molar yield of perfluorohexanoic acid (PFHxA) was 1.3%, which was lower than that in soil or mixed bacteria culture system in other studies. At Day 28, 5.5% of 6-2 FTOH were still detectable in the closed bottle system. Based on the results of this study, monitoring and toxicity test on the stable metabolites of FTOH degradation should be strengthened so as to make a comprehensive risk assessment of 6-2 FTOH.