Anaerobic biotransformation of N-methyl perfluorobutanesulfonamido ethanol and N-ethyl perfluorooctanesulfonamido ethanol.

Some fluorochemical products are manufactured using N-methyl perfluorobutanesulfonamido ethanol (MeFBSE), a short-chain replacement for perfluorooctyl-based chemistries N-methyl and N-ethyl perfluorooctanesulfonamido ethanols (EtFOSE). The present study shows for the first time the anaerobic biodegradation of MeFBSE and EtFOSE in municipal digester sludge under methanogenic conditions. Both MeFBSE and EtFOSE were incubated for 108 d with anaerobic digester sludge. Although sterile controls did not remove MeFBSE, it was degraded in live sludge. The loss of MeFBSE coincided with production of N-methyl perfluorobutanesulfonamido acetate (MeFBSAA) and perfluorobutane sulfinate (PFBSI). The biodegradation appeared biphasic, with pseudo first-order loss between days 0 and 70, resulting in approximately 75% removal but no further depletion of MeFBSE between days 70 and 108. By day 108 MeFBSAA and PFBSI accounted for 57 and 40 mol% of initial dose, respectively. Mass balance values in live cultures on days 0, 10, 21, 29, 70, and 108 were 103, 92, 94, 100, 93, and 122%, respectively. The apparent first-order biodegradation rate constant for MeFBSE over the first 70 d was 0.0194 d , and the apparent half-life was 35.8 d. Incubation of EtFOSE with live digester sludge resulted in low-level formation of N-ethyl perfluorooctane-sulfonamido acetate and perfluorooctane sulfinate, which did not form in sterile controls. Although it was not measurably lost, 2 to 3% loss of EtFOSE was calculated based on product concentrations. The total product formation rate constant was determined by first-order kinetic evaluation over the first 72 d to estimate a first-order biodegradation rate constant for EtFOSE at 0.000374 d , and the apparent half-life time was 1860 d. Environ Toxicol Chem 2018;37:768-779. © 2017 SETAC.