Benzylalkyldimethylammonium (BACs), dialkyldimethylammonium (DDACs), and alkyltrimethylammonium compounds (ATMACs) are quaternary ammonium compounds (QACs) widely used in industrial and consumer products. Nevertheless, little is known about their fates in wastewater treatment plants (WWTPs). We detected 7 BACs, 6 DDACs, 6 ATMACs, and 8 hydroxy- and carboxyl- metabolites of BACs (BACm) in wastewater collected from a WWTP in New York State. The median concentrations of ∑All (sum concentration of all 27 analytes) in influent and final effluent were 31900 and 545 ng/L, respectively, which corresponded to a removal efficiency of 98 %. C14-BAC, C10-DDAC, C18-DDAC, and C16-ATMAC were the major compounds found in influent (collectively accounting for 62 % of ∑All), suggestive of their prevalent usage in consumer products. BACm were detected for the first time in wastewater (median: 1720 ng/L in influent), and they comprised 8-11 % of ∑All in wastewater, which highlighted the importance of monitoring QAC metabolites in wastewater. The mass loadings of QACs into the WWTP were in the range of 1480-10700 mg/d/1000 inhabitants, whereas the corresponding emission rates were in the range of 119-7720 mg/d/1000 inhabitants. QACs present in final effluents may exert low to moderate risks on aquatic organisms, which warrants more attention.