Occurrence and fate of benzothiazoles and benzotriazoles in constructed wetlands

A suite of benzothiazoles and benzotriazoles was analysed by comprehensive multi-dimensional gas chromatography coupled to time-of-flight mass spectrometry in four different wastewater treatment systems. The selected wastewater treatment systems include one conventional wastewater treatment plant (WWTP) and for the first time, two constructed wetlands. Although benzothiazole (BT), 2-(methylthio)benzothiazole (MTBT), 2-hydroxybenzothiazole (OHBT) and benzotriazole (BTri) occurred in all the raw wastewater samples, 4- and 5-methylbenzotriazoles (4- and 5-TTri) were only detected in the industrially impacted wastewater. Concentrations of benzothiazoles and benzotriazoles in raw wastewater ranged from 0.2 to 2.2 μg L⁻¹ and from 0.06 to 36.2 μg L⁻¹, respectively. The benzothiazoles removal efficiencies ranged from zero to up to 80% in the conventional WWTP and from 83 to 90% in constructed wetlands. For BTri, removal efficiencies ranged from 65 to 70% and from 89 to 93% in conventional WWTP and constructed wetlands, respectively. The higher performance of CWs in the removal of these compounds might be attributed to the contribution of biodegradation, photodegradation and plant uptake.