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

Abstract

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, non‐stick, 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. Here we utilized microbial microcosms from 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, (F7C3OCHFCF2SCH2CH2OH (FESOH), F3COCHFCF2SCH2CH2OH (MeFESOH), F7C3OCHFCF2OCH2CH2OH (ProFdiEOH), F7C3OCHFCF2CH2OH (ProFEOH), F3COCHFCF2OCH2CH2OH (MeFdiEOH)), and their select transformation products, were incubated in WWTP aerobic microcosms to determine structure‐activity relationships. 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 (F7C3OCHFC(O)OH (2H‐3:2 PFECA), and F3COCHFC(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 d. Surface water Photofate experiments compared 2H‐1:2 PFECA, and 2H‐1:2 PFESA to 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 in studying novel PFAS functionalization.