Wausau utility debates when to replace PFAS-filtering carbon as levels rise

Wausau Waterworks staff told the Waterworks Commission on Aug. 5 they are seeing early breakthrough of PFOA and PFOS in the GAC treatment vessels and asked the commission whether to trigger a media replacement now or wait until a regulatory-level trigger is reached.

The issue matters because the city built a new treatment train with 12 tall vessels to remove PFAS, and replacing the carbon in all vessels would cost in the low seven figures. The choice affects near-term operating budgets, ratepayer bills and compliance planning as federal and state guidance evolves.

Staff consultant Susan (Donahue) said the project was designed for flexibility and "ultimately, we, selected the alternative 1, which was 12 tall vessels for granular activated carbon." She described the vessels as operating in a lead–lag configuration that lets the utility rotate media between a working bed and a lag bed. Staff samples 18 PFAS compounds at multiple ports in each vessel and reported that PFOA and PFOS are the compounds showing the most movement through the beds.

The utility director noted…