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.
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.
Testing PFAS in Wastewater (Environmental Protection Agency)
In addressing the near-term regulations for PFAS in drinking water, OWASA hopes to reduce PFAS levels in the community’s wastewater as well. We continue to closely monitor PFAS in our drinking water and wastewater and hope to identify any correlations between reducing PFAS in drinking water and reduced PFAS levels in wastewater discharge and biosolids.
OWASA is working with a consultant to perform an assessment to better understand the sources within our wastewater system. At this time, we are not aware of any significant industrial users in the service area that could be a concentrated source of PFAS in wastewater.
Wastewater data
Of 40 PFAS compounds tested, 9 were found in our wastewater influent and 5 were in our effluent in our most recent testing (November 2024). At this point, we are not certain why the number of detections increases in the treatment process. You can see results on the analysis from our monitoring program by selecting the relevant tabs on our monitoring dashboard below.
OWASA Biosolids Management
Like other wastewater treatment plants across the country, OWASA’s wastewater treatment process produces a nutrient-rich material called biosolids that has beneficial uses in agriculture by improving soil quality and stability. We apply these biosolids to OWASA-owned land and provide it to farmers in Orange, Chatham, and Alamance counties in accordance with state permits and regulations. What we don’t apply to land as biosolids, we compost into a soil additive in partnership with a regional composter. In 2023, through land application and composting, we recycled more than 1,050 dry tons of biosolids through this program.
Partnerships with local farms to land-apply biosolids are a cost-effective way for OWASA to manage our community’s highly treated waste. OWASA has considered alternative approaches to managing the community’s biosolids (such as 100% composting, and landfilling); however, all of these options come at a considerable cost to OWASA ratepayers and were historically not supported by farmers participating in our land application program. At this time, the wastewater treatment process implemented at OWASA’s Mason Farm Wastewater Treatment Plant is not designed to remove PFAS. OWASA has never applied biosolids from our wastewater treatment process in the watersheds that drain to and supply our drinking water sources: the Cane Creek Reservoir and University Lake watersheds.
The methodology for PFAS testing in biosolids has only recently been approved by the EPA. OWASA began testing its biosolids for PFAS in August 2022. The EPA was expected to release its report in late 2024, on some PFAS compounds in biosolids, which will help inform any future regulations of PFAS in biosolids. In December 2024, stakeholders submitted a report to the EPA, Stakeholder Meeting Facilitation for Issues Related to PFAS and Biosolids, summarizing workshops held in 2023 and 2024 facilitated by the National Association for Clean Water Agencies, the EPA and other stakeholders.
The science related to monitoring, managing, and understanding the health impacts of PFAS in biosolids is still being developed. A holistic approach, interrupting the life cycle of PFAS in our environment, is our long-term goal.
Biosolids Data
We are committed to understanding how PFAS migrates through our processes and supporting research and regulations.
Out of the 40 compounds we tested for, our most recent biosolids analysis (November 2024) detected 16 PFAS compounds in our dewatered biosolids and 6 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 2024. 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)