Transformation of Biocides Irgarol and Terbutryn in the Biological Wastewater Treatment

The biocides irgarol and terbutryn enter the wastewater treatment plant (WWTP) via combined sewer systems after leaching from coatings and paints of materials. In this study, the biotransformation of irgarol and terbutryn was examined in aerobic batch experiments with activated sludge taken from the nitrification zone of a conventional WWTP, since currently there is no information about the fate of irgarol and terbutryn in biological wastewater treatment. Both, irgarol and terbutryn were transformed into one main transformation product (TP) following pseudo first-order kinetics. The TPs were tentatively identified by high-resolution mass spectrometry (HR-MS) to be irgarol sulfoxide and terbutryn sulfoxide. The final confirmation of the proposed chemical structures of the TPs was achieved by a comparison of mass spectra and nuclear magnetic resonance (NMR) spectra with those of authentic reference standards (e.g., synthesized). An analytical method for the sensitive quantification of irgarol, terbutryn and their TPs in environmental samples was developed based on solid phase extraction (SPE) and LC tandem MS detection. Irgarol sulfoxide and terbutryn sulfoxide were detected in the effluents (average concentrations up to 22 ng L^–1 and 65 ng L^–1) of all four investigated WWTPs as well as in streams and small rivers (up to 14 ng L^–1 and 34 ng L^–1). Luminescent bacteria inhibition test with <i>Vibrio fischeri</i> exhibited that the TPs irgarol sulfoxide and terbutryn sulfoxide feature a similar bacterial toxicity than the parent compounds