Photocatalytic treatment of metronidazole-containing wastewater

The presence of antibiotics in wastewater is risky for the environment as the conventional wastewater treatment plants are not always capable of removing them completely. Therefore, antibiotics may enter the water bodies and affect the health of aquatic living organisms. In this work, the effluent after the continuous flow activated sludge process was collected and analyzed. The average total organic carbon (TOC) and metronidazole (MNZ) concentrations were 43 ± 13.1 mg/L and 5.3 ± 0.2 mg/L, respectively. The catalytic activities of TiO, TiO2, Bi2O3, and WO3 were tested under the visible light (VIS, 500 nm) and near-visible ultraviolet light (UV, 365 nm) irradiations. The structure and properties of the catalysts have been verified using SEM-EDX and Mastersizer 3000. 25% of MNZ have been degraded under VIS only after 150 min. Even though all four catalysts were able to degrade MNZ to some extent (28-33%) after 150 min of VIS irradiation, they were not able to mineralize the organic compounds of the wastewater. On the other hand, the application of UV alone and with the catalysts resulted in the complete degradation of MNZ. Moreover, UV/TiO2 achieved 52% TOC removal after 150 min of the experiment.