Removal of polar UV stabilizers in biological wastewater treatments and ecotoxicological implications

• The removal of two benzotriazoles (BZTs) was investigated in 20 WWTPs.
• Both BZTs were observed in all influent and effluent samples.
• MeBZT showed higher concentrations and lower removal rates than BZT.
• Larger hydraulic retention times do not guarantee higher removal rates.
• MeBZT may represent a hazard for different aquatic organisms.

The present study describes the development, validation and application of a fully automated analytical method based on on-line solid-phase extraction–liquid chromatography–tandem mass spectrometry (on line SPE–HPLC–MS/MS) to assess the removal efficiency in water works and the ecotoxicological implications derived of the two most used benzotriazole-class UV stabilizers (BZTs), namely 1H-benzotriazole (BZT) and 5-methyl-1H-benzotriazole (MeBZT). Influent and effluent wastewater samples from 20 wastewater treatment plants (WWTPs) were analyzed. Removal rates (RE%) and half-lives (t1/2) for each BZTs were calculated and correlated to the hydraulic retention time (HRT) of each plant. Both BZTs were detected in all influent and effluent samples (concentrations in the range 26.7 ng L−1–42.9 μg L−1), with the highest concentrations corresponding to MeBZT. Results indicated that both compounds were recalcitrant (RE% in the range 11.8–94.7%) and that no clear influence of HRT on removals could be drawn.Finally, the potential environmental risk posed by the levels of BZTs detected was evaluated calculating the hazard quotients (HQs) MeBZT was the only BZTs posing a risk to Vibrio fischeri, Daphnia galeata and Pimephales promelas.