A Comparative Biodegradation Study to Assess the Ultimate Fate of Novel Highly Functionalized Hydrofluoroether Alcohols in Wastewater Treatment Plant Microcosms and Surface Waters.

Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals present in a wide range of commercial and consumer products due to their water-repellency, nonstick, or surfactant properties, resulting from their chemical and thermal stability. This stability, however, often leads to persistence in the environment when they are inevitability released. We utilized microbial microcosms from wastewater treatment plant (WWTP) sludge to determine how employing different functional groups such as heteroatom linkages, varying chain lengths, and hydrofluoroethers (HFEs) will impact the ultimate fate of these novel PFAS structures. A suite of five novel fluorosurfactant building blocks (FCOCHFCFSCHCHOH (FESOH), FCOCHFCFSCHCHOH (MeFESOH), FCOCHFCFOCHCHOH (ProFdiEOH), FCOCHFCFCHOH (ProFEOH), and FCOCHFCFOCHCHOH (MeFdiEOH)) and their select transformation products, were incubated in WWTP aerobic microcosms to determine structure-activity relationships. The HFE alcohol congeners with a thioether (FESOH and MeFESOH) were observed to transform faster than the ether congeners, while also producing second-generation HFE acid products (FCOCHFC(O)OH (2H-3:2 polyfluoroalkyl ether carboxylic acid [PFECA]) and FCOCHFC(O)OH (2H-1:2 PFECA). Subsequent biodegradation experiments with 2H-1:2 PFESA and 2H-1:2 PFECA displayed no further transformation over 74 days. Surface water Photofate experiments compared 2H-1:2 PFECA, and 2H-1:2 polyfluorinated ether sulfonate (PFESA) with their fully fluorinated ether acid counterparts, and demonstrated the potential for both HFE acid species to completely mineralize over extended periods of time, a fate that highlights the value of studying novel PFAS functionalization. Environ Toxicol Chem 2024;43:2297-2305. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.