PFAS in wastewater

PFAS and wastewater treatment plants

Nearly all municipal wastewater treatment plants have measurable levels of PFAS in their discharge. The vast majority of that PFAS comes from upstream sources — such as industries, household products, and human waste — and flows through the facilities.

Available treatment technologies do not destroy PFAS. Some PFAS compounds can undergo transformation within the treatment plant, complicating the measurement of influent and effluent levels. And PFAS compounds will move around between the liquids and solids produced in current treatment processes.

In 2022, we completed a study of PFAS levels going into and coming out of three wastewater treatment plants. This study is helping us understand that PFAS are present in wastewater discharges, typically at levels below Washington Department of Health state action levels for the protection of drinking water.

Using water quality permitting to control PFAS discharge into the water

In December 2022, EPA issued new guidance on PFAS water quality permitting for state agencies. We are reviewing this guidance and are in the process of evaluating and including appropriate requirements, such as monitoring or source-reduction studies, in water quality permits on a case-by-case basis. EPA is also developing test methods for PFAS in wastewater, which will help us improve monitoring in permits.

PFAS contamination at military bases, including those in Washington state, is common due to the use of firefighting foam containing PFAS chemicals. In response, EPA is starting to include PFAS monitoring and management practices in permits for federal facilities, like military bases. We will continue to use our Clean Water Act Section 401 certification authority to ensure appropriate requirements are included in EPA-issued federal permits in Washington state.

Ongoing research

In addition to the 2022 study on PFAS within wastewater treatment plants, we completed a study in 2021 looking upstream of those plants. To complete the study, Chemicals of Emerging Concern in Pretreated Industrial Wastewater in Northwestern Washington State: Screening Study Results, 2021, we measured PFAS in wastewater from a range of different industries that discharge to the sanitary sewer. This study is part of our effort to understand the origins, processes, and pathways by which PFAS and other chemicals of emerging concern (CECs) enter domestic wastewater systems. This will help us prevent or minimize the introduction of PFAS into wastewater in the first place.

We plan to conduct a further sampling study of PFAS in influent and effluent at wastewater treatment plants with significant industrial contributions, to help us determine what additional regulatory requirements are appropriate.

Addressing PFAS contaminated groundwater at construction sites

Most construction sites in Washington are required to obtain coverage under the Construction Stormwater General Permit to control and reduce water pollution. When a construction site identifies PFAS contamination, we issue a companion order to our permit coverage that requires treatment and monitoring to evaluate the effectiveness of that treatment. This will help us learn more on the effectiveness of stormwater treatments at reducing PFAS.