Per- and polyfluoroalkyl substances (PFAS) in wastewater streams: occurrence and current treatment

PFAS are a growing environmental concern due to their persistence and universality. PFAS enter the environment through multiple channels, one of which is wastewater. This study comprehensively presents PFAS in wastewater streams from point- and non-point sources, and discusses the variability. 55 papers have been included in this review. This review highlights a high variability of total PFAS in WWTP effluents with concentrations ranging from 16.8 ng/L to 11,870 ng/L depending on the number of PFAS tested, the types of industries the WWTPs served, the effluent treatment processes used, and if the influents are contaminated by aqueous film forming foam. DWTP effluents generally have significantly lower PFAS due to cleaner influents. Often, effluents contain more PFAS than influents because of the degradation of PFAA precursors. Landfill leachate contains comparatively more PFAS (as high as 291,700 ng/L) and the factors affecting their levels are the types and volumes of waste received, and leachate treatment used. Membrane treatment reduces PFAS in leachate significantly, but they are retained in the concentrate, which sometimes contains higher total PFAS concentrations than untreated leachate. PFAS in the concentrate of membrane treatment can be removed with advanced technologies such as activated carbon, ion exchange resins and electrochemical treatment. Non-point sources of PFAS comprise mainly runoffs and stormwater. Landfills without leachate collection and treatment systems constitute a non-point source of PFAS. Actual firefighting and firefighting training are important non-point sources of PFAS contributing up to 51.4 mg/L of PFAS in groundwater. PFAS from non-point sources are currently understudied.