The efficiency of persulfate (PS) alone, UV-C activated TiO2 (UV/TiO2), UV-C activated PS (UV/PS) and UV/PS with TiO2 (UV/PS/TiO2) in the oxidative removal of metronidazole (MNZ) was studied. In addition, applicability of UV/PS process in batch and continuous photo-reactors (BPR and CPR) was investigated. The performance of BPR and CPR was assessed in terms of energy consumed and electrical energy per order (EEO), which indicated that both UV/PS and UV/PS/TiO2 systems were energy efficient. On the other hand, MNZ removal kinetics has revealed a higher MNZ removal rate of 0.232 min−1 in UV/PS/TiO2 system and showed a pseudo-first-order kinetics (r2 > 0.96). Furthermore, the effect of influent anion concentration (i.e. Cl−, SO42−, NO3− and their combinations) on UV/PS system was examined. The sequence of MNZ removal (from highest to lowest) in the presence of anions was (SO42− + Cl− + NO3−) > (SO42− + NO3−) > SO42− > (SO42− + Cl−) > Cl− > NO3−. An oxidative degradation pathway of MNZ in UV/TiO2 system was proposed. The toxicity of treated samples was evaluated using micro-toxicity assay against V. fischeri. The percentage inhibition of effluent samples to V. fischeri was within 15%, which denotes the suitability of CPR for real-time application.