Temporal Concentrations of Quaternary Ammonium Compounds in Wastewater Treatment Effluents During the COVID-19 Pandemic, 2020-2021.

Quaternary ammonium compounds (QAC) are high production chemicals used in many commercial and household disinfection products. During the SARS-CoV-2 (COVID-19) pandemic, QACs were included on lists of COVID-19 disinfectants. Increased QAC use could lead to higher levels of QACs in wastewater treatment plant (WWTP) effluents, which could subsequently be released into the environment. To evaluate QACs in WWTP effluent, three WWTPs in the northeastern United States were monitored from May 2020 through August 2021. Target QACs included six benzylalkyldimethyl ammonium compounds (BAC), three dialkyldimethyl ammonium compounds (DADMAC), two ethylbenzylalkyldimethyl ammonium compounds (EBAC), and benzethonium. At least one QAC was detected in every sample with individual concentrations up to 1,600 ng L^-1. BAC-C₁₄ was detected most frequently, found in 93% of effluent samples; BAC-C₁₂, BAC-C₁₆, EBAC-C₁₂ and EBAC-C₁₄ were all detected in greater than 80% of samples. Few temporal patterns were observed in QAC concentrations with respect to weekly COVID-19 cases: at WWTP 2, DADMAC-C₈:C₁₀ and DADMAC-C₁₀ were positively correlated, and DADMAC-C₈ negatively correlated. There were several seasonal trends at WWTP 1, including significant differences of ƩDADMAC, which were higher in fall than summer; ƩBAC was higher during the fall than both spring and summer; and ƩQAC where higher during the fall than spring.