PFAS Through Conventional Treatment
Municipal wastewater treatment plants were designed to remove biological oxygen demand, nutrients, and pathogens — not dissolved fluorochemicals. Conventional activated sludge treatment removes some PFAS through sorption to biosolids and limited biodegradation, but a substantial fraction of dissolved PFAS passes through treatment plants in the liquid effluent. Studies of wastewater treatment plant influent and effluent consistently show PFAS removal rates of 30 to 80 percent for individual compounds, with significant residual PFAS in treated effluent.
Partitioning to Biosolids
During wastewater treatment, a fraction of PFAS — particularly longer-chain compounds with higher organic carbon binding affinity — partitions from the liquid to the solid biosolids fraction. This partitioning concentrates PFAS in biosolids, which are then either land-applied as fertilizer, incinerated, or landfilled. Each disposal pathway creates a secondary PFAS environmental release: land application contaminates soil and groundwater; incineration requires high temperatures for complete destruction; landfilling may leach PFAS into groundwater via leachate.
Treatment Plant Effluent as a PFAS Source
Treated wastewater effluent discharged to surface water can be a significant PFAS loading source, particularly in watersheds where surface water is used for downstream drinking water. The combination of wastewater effluent PFAS loading and stormwater PFAS inputs creates persistent PFAS levels in many rivers and reservoirs used as drinking water sources. Water treatment plants withdrawing from these sources face an ongoing PFAS challenge that reflects the entire upstream PFAS use profile of their watershed.
Advanced Treatment at Wastewater Plants
Some wastewater treatment plants in highly PFAS-contaminated watersheds have installed advanced treatment specifically for PFAS — typically granular activated carbon or membrane systems. These upgrades are expensive and require ongoing media management, but represent the only currently available means of substantially reducing PFAS loading from wastewater plant effluent. EPA has proposed effluent limitation guidelines for PFAS in wastewater from semiconductor manufacturing — the first sector-specific PFAS wastewater limits — with broader industrial sector guidance expected to follow.