Influence of Conjugation on the Fate of Pharmaceuticals and Hormones in Canadian Wastewater Treatment Plants

Abstract

The concentrations of 30 pharmaceuticals and 17 hormones in influent, effluent, and biosolid samples were determined at 19 representative Canadian wastewater treatment plants (WWTPs). Many pharmaceuticals and hormones are excreted by humans in conjugated forms that are not detected by analytical techniques aimed at free analytes. Conjugation can be reversed by naturally occurring enzymes that are found in WWTPs, the collection system, and/or the environment. In this study, we applied deconjugating enzymes (β-glucuronidase/sulfatase) to an aliquot of each sample in order to release target analytes from their glucuronate and sulfate forms. Of the pharmaceuticals evaluated, deconjugation during wastewater treatment only influenced the fate of lamotrigine in lagoons as well as secondary and advanced treatment facilities, but not a primary treatment plant. Several hormones arrived at the WWTPs in part in a conjugated form, and our data indicate that some of the conjugated forms of mestranol and testosterone survived wastewater and/or biosolid treatments. Therefore, mestranol and testosterone may eventually become deconjugated and hence become more prevalent in the natural environment. This study demonstrates the utility of deconjugating enzymes for screening the impact of conjugation and deconjugation processes and more accurately quantifying the occurrence and removal of pharmaceuticals and hormones in WWTPs.