The Characteristic And Mechanism For Enhanced Removal Of Organic Matters In The Electro-Hybrid Ozonation-Coagulation (E-HOC) System

In order to improve the limitation of organic matters removal in conventional advanced wastewater treatment process,and strengthen the removal of dissolved organic matters in wastewater treatment plant effluent,and control the health risk of wastewater reclamation,the Electro-Hybrid Ozonation-Coagulation?E-HOC?process was developed.Effluent from some wastewater treatment plant was selected to analyze the characteristics and mechanism for enhanced removal of organic matters in the E-HOC process.It provided theoretical basis for the enhanced removal of organic matters in wastewater treatment plant effluent.Changing the current density?5,10,15,20 mA/cm²?,ozone dosage?1.0,1.5,2.0mgO₃/mg DOC?and initial pH values?5,7,9?to investigate the characteristics of organic matters in the E-HOC process.The results showed that the averaged DOC,UV₂₅₄ and colour removal efficiency were 58.6%,61.36%and 72.22%,respectively at pH=5,1.5mgO₃/mgDOC and 15 mA/cm²,which was the best experimental parameters for the E-HOC process.The capacity of removing organic matters in E-HOC process was superior to the conventional electrocoagulation and the single ozonation processes.The removal efficiency of DOC in the E-HOC process increased by 20.03%and46.42%,respectively.The enhanced removal ways of organic matters in the E-HOC process included coagulation of aluminum polynuclear hydroxyl hydrolysate generated by aluminum anode ionization,direct ozone molecular oxidation and indirect hydroxyl radical oxidation.To analyze the production pathway of hydroxyl radical in the E-HOC process,phosphate was introduced into the system,and the DOC removal efficiency was significantly suppressed,which suggested the surface hydroxyl groups may be the active reaction sites for catalytic ozonation.According to the fourier transform infrared spectroscopy?FT-IR?and X-ray photoelectron spectra analysis,the results further proved that the hydroxyl groups on the surface of the coagulant reacted with ozone.Meanwhile,the·OH in the E-HOC process was determined by p-chlorobenzoic acid?pCBA?probe method and Electron Paramagnetic Resonance?EPR?experiment.The results showed that E-HOC process produced more·OH than the single ozonation process,indicating that the aluminum coagulant could act as a catalyst to catalyze ozone to produce more·OH.Then,adding the isopropyl alcohol?IPA?,catalase?CAT?and the benzoquinone?BQ?,with the IBP as the target pollutants,we conducted a series of quenching experiments.The study indicated that·OH,·O₂^-and H₂O₂ all existed in the E-HOC process.Due to the formation of H₂O₂,the peroxide reaction?O₃/H₂O₂?may occur in the E-HOC process.The formation of·OH by peroxide reaction was another way to enhance the removal of organic matters.In addition,ozone in the system can react with OH^-produced in solution or on the cathode,thereby triggering a chain reaction to produce·OH.