Wastewater Treatment Facilities as Underappreciated Point Sources for Per- and Polyfluoroalkyl Substances and Microplastics: A Critical Perspective

Per- and polyfluoroalkyl substances (PFAS) and microplastics (MPs) represent two classes of contaminants that are prevalent in the environment and pose significant health risks to micro- and macrobiota and to ecological systems. For example, emissions of PFAS and MPs into the environment range from thousands (PFAS) to millions (MPs) of tonnes per year. There are many studies probing the fate and transport of these “forever” chemicals in natural and engineered aquatic systems, as well as studies investigating mechanisms of PFAS interactions with MPs in water. However, there is limited information regarding PFAS–MP behavior within wastewater treatment plants (WWTPs). Wastewater treatment may be an important nexus for PFAS and MPs to be introduced into environmental waters and drinking water sources, given that the Environmental Protection Agency has identified that WWTPs can act as important, centralized vessels for PFAS loads and discharge. WWTPs similarly collect thousands of MPs from laundry, household products (e.g., plastic containers), and personal care products (e.g., microbead exfoliators). In this critical perspective, we highlight (i) properties of PFAS and MPs that drive their interactions in water; (ii) transport and distribution of PFAS, MPs, and PFAS-associated MPs during wastewater treatment; and (iii) opportunities for the separation of PFAS and MPs via forced air–water partitioning in engineered treatments. We end the perspective with insights into future research directions and overlooked complications in characterizing PFAS and MP transport and treatment within WWTPs.