PFAS in wastewater

Through monitoring and sampling efforts across the country and in Washington, we know that the two main types of wastewater discharges that are likely to contain some level of PFAS are municipal wastewater treatment plants and industrial facilities. Because PFAS is persistent, highly resistant to treatment, and nearly ubiquitous in the environment, preventing contamination of municipal and industrial wastewaters in the first place is the most effective way to protect water quality.

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 guidance on PFAS water quality permitting for state agencies. We have reviewed this guidance and have started evaluating and including appropriate requirements, such as monitoring or source-reduction studies, in water quality permits on a case-by-case basis.

As Ecology issues and reissues permits for major municipal wastewater treatment plants and industries that use or produce PFAS, we are including PFAS monitoring requirements. Municipalities that have authorized industrial pretreatment programs must investigate and control industrial sources discharging into their sewer systems. Source investigation and control has proven successful in greatly reducing the amount of PFAS coming into wastewater treatment facilities in other states. Examples of permits where we have recently added in these types of requirements include some of the biggest facilities in the state: West Point (King County), Everett, and Tacoma Central.

Additionally, the reissued Industrial Stormwater General Permit, effective January 1, 2025, requires monitoring and reporting of the six PFAS compounds found in the Safe Drinking Water Act for Waste Management and Remediation Services and Air Transportation facilities. The results from monitoring and source identification will help us better understand how to control PFAS discharges through source reduction. It will also help inform and develop future effluent limits.

EPA has developed an analytical method for measuring 40 different PFAS chemicals in wastewater, EPA Method 1633, which helps us better characterize wastewater discharges. In August 2024, Ecology adopted water quality criteria for PFOA and PFOS for aquatic life in fresh and marine water. These must be approved by EPA before we can use them in NPDES permitting. EPA has also proposed recommended water quality criteria for the protection of human health for PFOA, PFOS, and PFBS. When these criteria are published, we will determine whether to adopt these into state standards.

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.

Biosolids General Permit

Biosolids are generated as a byproduct of the wastewater treatment process and can serve as a nutrient-rich soil amendment when applied properly, as managed under the biosolids general permit. PFAS from the wastewater entering a treatment plant can persist in these biosolids. To learn more, visit the biosolids webpage for information on the permit, current permittees and contacts.

Ongoing research

In addition to investigating PFAS within wastewater treatment plants, we completed a study in 2021 - Screening Study Results, looking upstream at pretreated industrial wastewater. 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 that 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.

Contact information

Madison Hattaway
CEC Coordinator
madison.hattaway @ecy.wa.gov
360-628-2924