Deciphering the impact of wastewater treatment plants from other inputs on quaternary ammonium compounds (QACs) in surface waters and sediments

Abstract

Quaternary ammonium compounds (QACs) are widely used and have numerous routes to the environment. This work assessed the levels of QACs in surface waters that receive treated wastewater effluent. Samples were collected over a 27-month period from eight different surface waters including rivers, lakes, and a coastal bay. The total summed concentration of 21 targeted QACs including benzylalkyldimethylammonium compounds (BACs), ethylbenzylalkyldimethylammonium compounds (EtBACs), alkyltrimethylammoinium compounds (ATMACs), and dialkyldimethylammonium compounds (DADMACs), were 100 -1000 ng/L in surface waters and 500 -2000 ng/kg in associated sediments of four rivers, three lakes, and one coastal bay. Based on the profiles of the individual QACs present, surface water exhibited greater compositional similarity to wastewater effluent than sediment, and effluentderived QAC signatures influenced downstream waters but were modulated by environmental processes or other inputs of QACs. This finding was supported by mass balance calculations, which revealed that the median fraction of QACs attributed to the local wastewater effluent input of the surface water varied from 0.5 to 76% for the four rivers and 1% and 53% for two of the lakes. These results indicate that the QAC profile in a given surface water will be driven by inputs and environmental processes, and that at a given site, the load of QACs likely arises from a combination of inputs and not wastewater effluents alone.