PFAS & Your Water: Wastewater and Biosolids Monitoring
Wastewater that arrives at our Mason Farm Wastewater Treatment Plant (referred to as influent) contains PFAS at levels summarized in the dashboard below. There are a number of potential sources of PFAS in the wastewater arriving there, including household products and a pass-through of our treated drinking water (link to Drinking Water and Monitoring tab).
Our wastewater treatment process does not remove PFAS. As a result, PFAS can be detected in the treated wastewater (referred to as effluent), as well. PFAS has also been detected in our biosolids, the byproduct we make during the wastewater treatment process. OWASA produces Class A Exceptional Quality biosolids as defined by the EPA. We manage them through land application on OWASA owned and private property in partnership with local farmers; and by composting with a local company. Both end uses are regulated by federal and state laws.
PFAS presence in wastewater effluent and biosolids is the result of PFAS persisting after they are thoroughly treated at the wastewater treatment plant. We are monitoring existing technologies for effluent and developing technologies for biosolids that could prove to be successful for PFAS removal in the future. We look forward to new science, technology and regulations that will inform and guide our next steps on what’s best and viable for the environment and our neighbors downstream.
Wastewater and Biosolids Data: The data below show our monitoring results for PFAS in wastewater influent, effluent, and biosolids.
Wastewater data
Of 40 PFAS compounds tested, six were found in our wastewater influent and nine were in our effluent in our most recent testing (November 2023). At this point, we are not certain why the number of detections increases in the treatment process. The following table summarizes the range of PFAS levels detected in the influent to and effluent from our wastewater treatment plant. You can see results on the analysis from our monitoring program by selecting the relevant tabs on our monitoring dashboard below.
Biosolids Data
The EPA is in the process of validating a testing method for biosolids sampling. In the meantime, we used the best available science to analyze our biosolids samples for PFAS. We do not yet have guidance from regulatory agencies on what this data indicates, nor what to aim for in the future. Nonetheless, we are committed to understanding how PFAS migrates through our processes and supporting research and regulations. Later this year (2024), we anticipate that guidance from state and federal agencies will help us analyze the data and plan our next steps for managing PFAS in biosolids.
Out of the 40 compounds we tested for, our most recent biosolids analysis (November 2023) detected 24 PFAS compounds in our dewatered biosolids and 20 PFAS compounds in our liquid biosolids. HFPO-DA (Gen-X) was not detected. The following table includes the results for our quarterly biosolids monitoring program from August 2022 through November 2023. Please note that the units for biosolids are different than the units in water PFAS analysis (ug/kg versus parts per trillion, since one is a concentration measure in a liquid (ppt) and the other is a concentration measure in a solid (ug/kg).
Link to Biosolids Sampling Analysis (pdf)
The current method for testing PFAS (1633) in wastewater is considered a “Draft Method,” meaning it is still being tested and refined. Learn more about the state of the science here:
Testing PFAS in Wastewater (Environmental Protection Agency)