A novel laboratory-scale continuous flow wastewater treatment system, consisting of an anaerobic moving bed biofilm reactor (AnMBBR) and an aerobic MBBR, was used for investigating the removal of hydroxybenzothiazole (OH-BTH) and selected benzotriazoles from municipal wastewater. The system was operated under three different Experimental Phases where different organic loadings were applied: 0.82 kg COD m-3 d-1 (Phase A), 0.2 kg COD m-3 d-1 (Phase B) and 2.1 kg COD m-3 d-1 (Phase C). The system achieved sufficient COD removal, nitrification and biogas production. All target micropollutants were partially removed during the experiments. Total removal efficiencies ranged from 32% for 5-methyl-1H-benzotriazole (5TTR) to 97% for OH-BTH. The contribution of the strictly anaerobic bioreactor was important for 5TTR, 5-chlorobenzotriazole (CBTR) and xylytriazole (XTR), while the use of aerobic bioreactors resulted to important increase of target compounds removal and it was exclusively responsible for the removal of OH-BTH and benzotriazole (BTR).