A Study On The Organic Matter Removal Characteristics And Mechanism In The Electro-hybrid Ozonation-coagulation System

The hybrid ozonation-coagulation（HOC）process enhanced the generation of hydroxyl radicals and improve the removal efficiency of organic matters.In order to further promote the high-efficiency removal process of dissovled organic pollutants in the secondary effluent of sewage plants,broaden the scope the application of the system,an E-HOC process was established to explore the removal characteristics and mechanism,and analyze the hydrolysed mechanism of different coagulants under electric field,which provided theoretical basis for the enhanced removal of organic matters in wastewater treatment plant effluent.The specific research results are as follows:To explore the removal characteristics of different E-HOC processes,the current density is 5,10,15 m A/cm²,the ozone dosage is 1.65 mg O₃/mg DOC,and the initial p H value is 5.The organic matter removal characteristics of Al-ME-HOC process（Al-E-HOC process with monopolar electrodes）,Fe-ME-HOC process,Al-BE-HOC process（Al-E-HOC process with bipolar electrodes）,Fe-BE-HOC process,Fe（+）-Al（-）-BE-HOC process and Al（+）-Fe（-）-BE-HOC process were compared.The results show that the E-HOC process with dual coagulation and bipolar electrodes has better organic removal efficiency than the E-HOC process with single coagulation and bipolar electrodes under the three current density conditions.Compared with the E-HOC process with monopolar electrodes（ME-HOC）,when Al or Fe is used as the coagulant,the E-HOC process with bipolar electrodes（BE-HOC）has a better removal efficiency on organic matters.In p H5,SOC effect plays important roles in E-HOC process under different current densities.In order to explore the effect mechanism of the coagulant generated in situ in different E-HOC processes on ozone,a series of quenching experiments were conducted to analyze the generation mechanism of hydroxyl radicals,·OH,·O₂^-and H₂O₂ all existed in the E-HOC processes.The results of the electron paramagnetic resonance（EPR）method show that dual coagulants were more efficiently activated O₃ to generate·OH compared with single Fe or Al coagulant.And the bipolar reaction system can more effectively catalyze ozone decomposition.The results of XPS further proves that compared with a single coagulant,the dual coagulant has higher catalytic activity and can more effectively promote the generation of·OH.Compared with the ME-HOC process,the bipolar electrode arrangement can improve the catalytic performance of the coagulant.In order to explore the influence of ozone oxidation on the hydrolysed species of different metal salt coagulants,Ferron colorimetric method and ESI time of flight mass spectra were used to explore the distribution of coagulant hydrolysed species produced by different anode electrolysis in EC and E-HOC systems,which is beneficial to better explain the mechanism of the process.The results show that ozone will affect the hydrolysed species of the coagulant,reduce the ratio of Al_a/Fe_a,increase the ratio of Al_b/Fe_b and Al_c/Fe_c.Therefore,the introduction of ozone can enhance the formation of-OH groups on the surface of the coagulant so as to promote the polymerization of Al/Fe species during the hydrolysis process.The arrangement of bipolar electrodes and dual coagulants are conducive to the formation of dominant hydrolysed species.At the same time,the co-hydrolysis of the dual coagulant can effectively improve the precipitation of the coagulant,which provides a new idea for improving the coagulation performance and controlling the residue of the coagulant.