Study On Integrated Wastewater Treatment Technology Of Electrocoagulation Membrane Dissolved Ozonation Flotation

In order to meet the increasingly stringent water quality requirements,this thesis integrated electrocoagulation,ozonation,flotation and membrane filtration to construct a novel electrocoagulation membrane dissolved ozone floatation（EMDOF）process.Under the premise of enhanced removal of organic matter,membrane fouling mitigation and simultaneous filtration and cleaning can be achieved through in-situ self-cleaning of the fouled membrane.The research is of great importance for enriching the wastewater recycling process.Taking secondary effluent from wastewater treatment plant（WWTP）as the research object,the thesis compared the effect of current density and ozone input dosage on EMDOF,optimized treatment conditions,and studied mechanism of organic matter enhanced removal and membrane fouling mitigation.The results showed that the EMDOF process was more efficient than the ECM（Electrocoagulation Membrane）and OM（Ozonation Membrane）process.Under the optimized condition,current density of 10 m A/cm² and ozone input dosage of 259.17 mg/L,EMDOF achieved removal efficiency of 35.22%,71.48%and 69.44%for DOC,UV₂₅₄ and chrominance,respectively.And the undetected turbidity was obtained.The result of EEM indicated humic acid could be removed through EMDOF.According to the results of Fourier transform infrared spectroscopy（FT-IR）and X-ray photoelectron spectrum（XPS）analysis,it was revealed that reaction between the hydroxyl group on the surface of coagulant and ozone could catalyze ozone decomposition to produce hydroxyl radicals.Membrane filtration experiment showed that ozone had significant inhibitory effect on flux declining.Particle size distribution and fractal dimension analysis showed that sludge particles of EMDOF were more amorphous and larger than that of ECM.The result of scanning electron microscope（SEM）indicated EMDOF formed porous and fluffy cake layer.The simultaneous filtration and cleaning experiments showed that the EMDOF process can maintain stable processing efficiency in continuous operation of990 min,and the normalized flux was stably recovered through the in-situ self-cleaning.According to the result of scanning electron microscope-energy dispersive spectrometer（SEM-EDS）,membrane fouling caused by filter cake layer was removed and the cleaning effect on fouling inside membrane was limited.In order to further verify the feasibility and applicability,EMDOF process was used to treat oilfield process wastewater containing polymers.The effect of organic matter removal and in-situ self-cleaning on flux recovery was evaluated.The experiment showed that effluent quality of EMDOF was better than that of OM or ECM,with better removal efficiency for COD,UV₂₅₄ and turbidity,and SS that meets the requirements of Water Treatment of Water Treatment in East Oilfield（Q/Sycq08011-2019）.Moreover,membrane fouling of EMDOF was reduced due to more dense cake layer formed by larger and more irregular flocs.According to the result of cleaning experiment,the normalized flux was recovered completely through in-situ self-cleaning.