Wixom WWTP Biosolids Fields Area of Interest (Wixom, Livingston County)

Sydney Ruhala, RuhalaS@Michigan.gov or 517-599-5356.

Christine Kosmowski, KosmowskiC@Michigan.gov or 517-599-6467.

The Michigan Department of Environment, Great Lakes, and Energy (EGLE), sampled the effluent (i.e. the treated wastewater discharged from the treatment plant) and biosolids for PFAS at the city of Wixom Wastewater Treatment Plant (WWTP) ) in 2018 as part of the Statewide Wastewater Treatment Plant and Biosolids PFAS Study. Results indicated that high levels of PFAS, specifically PFOS, were being passed through the treatment process at the plant. PFOS levels were 269 parts per trillion (ppt) in the effluent and 2,150 parts per billion (ppb) in the biosolids.

Biosolids are the nutrient-rich organic materials resulting from the treatment of domestic sewage in a WWTP. Biosolids can be a beneficial resource, contain essential plant nutrient and organic matter, and are recycled as soil conditioner.

The city of Wixom has an EGLE approved Residuals Management Plan, which has allowed the WWTP to land apply biosolids produced at the plant since 2000. The city of Wixom WWTP stopped land application of biosolids in the Spring of 2018 and has since sent accumulated sludge to a landfill. The city has worked with the sources of the PFOS--two industrial facilities that discharge wastewater to the WWTP--to install treatment to remove PFAS at the source and have since seen significant reductions in PFOS concentrations in both the effluent and biosolids generated at the WWTP.

Due to the high levels of PFOS found in the biosolids, EGLE evaluated land application sites that historically received biosolids from the city of Wixom WWTP. Following a field selection process which considered PFAS levels in biosolids, application amounts and rates, acreage used, soil types and other factors, five fields located in Livingston County were selected for sampling. The objective was to determine if there was any impact from the land application of industrially impacted biosolids containing high amounts of PFOS to the soil, groundwater, or adjacent surface water bodies. Crop and eventual beef sampling was also conducted by MPART.

Estimated groundwater flow direction varies across the site, including southwest, northwest, and northeast across the biosolids fields, depending on location.

Four residential wells and one livestock well adjacent to the biosolids fields were tested for PFAS in November 2019 as part of the investigation. All five wells were non-detect for PFAS. Out of abundance of caution, EGLE tested an additional 20 residential wells near the biosolids fields for PFAS in October 2021. PFAS was not detected in 18 of the 20 wells. Two wells had PFAS detections below the drinking water criteria. One of the two wells where PFAS was detected was also resampled in December 2021 and PFAS detections were below the drinking water criteria. The source of PFAS in the two residential wells with detections is unknown.

Content updated December 2023.

57 residential wells have been sampled. EGLE will expand residential drinking water well testing in the area if determined to be necessary.

EGLE will continue to work to determine the extent of PFAS contamination in the area of the biosolids fields.