Quaternary ammonium compounds (QACs) are high production volume chemicals used in consumer and industrial products, including disinfectants. Influent, effluent, and biosolid samples were collected from 12 wastewater treatment plants (WWTPs) from 2020 to 2023 and analyzed for 21 QACs to assess influent loadings and discharges to the environment via effluent and biosolids. The median total QAC concentrations in liquid influents ranged from 18 to 194 μg/L, while liquid effluent concentrations were