Comparison of ozone-based AOPs on the removal of organic matter from the secondary biochemical effluent of coking wastewater

Advanced oxidation processes (AOPs) based on ozone are gaining continuously growing popularity in wastewater treatment. This study explored the treatment of coking wastewater using a combination of ozonation (O-3), ultraviolet (UV), and hydrogen peroxide (H2O2) process expressed by % chemical oxygen demand (COD) removal, % total organic carbon (TOC), % UV254, % fluorescence intensity removal and its electrical energy consumption. The obtained results demonstrated that, the combination of O-3, UV, and H2O2 which is denoted by O-3/UV/H2O2 in this study achieved great success in COD removal (92.08%), TOC removal (78.25%), and reduction of fluorescence intensity (99.82%). Compared with the O-3 and O-3/UV processes, O-3/UV/H2O2 improved the COD removal by approximately 54-69% and 38-51%, respectively. In addition, the energy consumption was reduced by 53-67%. The TOC removal rate in the effluent ranged 71% and 83%, while the UV254 removal rate was up to 90%. The fluorescence spectroscopy showed that the O-3/UV/H2O2 combination process reduced the fluorescence intensity by almost 97% within 10 min. Furthermore, the total polycyclic aromatic hydrocarbons (PAHs) concentration in the effluent was less than 10 mu g/L (removal efficiency > 80%) and the most toxic benzo(a)pyrene (BaP) was less than 0.03 mu g/L (0.018 mu g/L). In addition, the energy consumption of the O-3/UV/H2O2 process was 53-67% lower than those of O-3 and O-3/UV processes. Furthermore, the energy consumption was 80.26 kWh m(-3) after 60 min of reaction time when the COD (69.3 mg/L) met the standard discharge. Finally, the O-3/UV/H2O2 process could be an effective method for improving the mineralisation of refractory organic matter.