Abstract
Some fluorochemical products are manufactured using N-methyl perfluorobutanesulfonamido ethanol (MeFBSE). MeFBSE is a short-chain replacement for perfluorooctyl based chemistries N-methyl and N-ethyl perfluorooctanesulfonamido ethanols (MeFOSE and EtFOSE, respectively). The present study shows for the first time the anaerobic biodegradation of MeFBSE and EtFOSE in municipal digester sludge under methanogenic conditions. MeFBSE and EtFOSE were incubated for 108 days with anaerobic digester sludge. MeFBSE was degraded in live sludge while sterile controls did not remove MeFBSE. The loss of MeFBSE coincided with production of N-methyl perfluorobutanesulfonamido acetate (MeFBSAA) and perfluorobutane sulfinate (PFBSI). The biodegradation appeared biphasic, with pseudo 1st 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 mole percent (mol%) and 40 mol% of initial dose, respectively. Mass balance 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 days was 0.0194 day−1 and the apparent half-life was 35.8 days. Incubation of EtFOSE with live digester sludge resulted in low level formation of N-ethyl perfluorooctane-sulfonamido acetate (EtFOSAA) and perfluorooctane sulfinate (PFOSI), which did not form in sterile controls. EtFOSE was not measurably lost, but 2–3% 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 days to estimate a first-order biodegradation rate constant for EtFOSE at 0.000374 day −1 and the apparent half-life time was 1860 days. This article is protected by copyright. All rights reserved
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