Photocatalytic ozonation of organic pollutants in wastewater using a flowing through reactor

Photocatalytic ozonation (PCO/O₃) process is a promising technology for mineralizing refractory organics in wastewater. In this study, we described an efficient approach to improve the mass-transfer performance of PCO/O₃ by using a helical photocatalytic module (HPM) in an annular UVC reactor. Under hydraulic retention time (HRT) of 19 min and influent phenol concentration of 33 mg/L (TOC 26 mg/L), TOC removal of 91.5% was obtained during a PCO/O₃ process with HPM, while TOC removal was only 58.1% without HPM (UVC/O₃). This flowing through reactor displayed good stability in a continuous test lasting 20 h. The electric energy required to reduce TOC by one order of magnitude per cubic meter of solution was calculated to be 10.23 kWh/(m³ order), which supported that the PCO/O₃ process in this flowing through reactor was energy-efficient compared with other processes (24.30-68.75 kWh/(m³ order)). The steel-rolling wastewater after biological treatment was taken as a target. Under the HRT of 57 min and initial COD of 124 mg/L, COD in effluent dropped to 45.8 mg/L and met the discharge standard of pollutants for municipal wastewater treatment plant of China.