Study On The Influence Of Pulse Electrocoagulation Electrooxidation Pretreatment On Membrane Fouling On Ultrafiltration Membrane

As the representative of the third generation drinking water treatment technology,ultrafiltration has a wide range of application in the field of water treatment.However,with the large-scale application of ultrafiltration equipment,membrane fouling has gradually become prominent,membrane flux has decreased,and osmotic pressure has increased.In the reuse of feed water and reclaimed water,the molecular weight of natural organic matter?NOM?mainly composed of humic acid?HA?is close to the molecular weight cut off of the ultrafiltration membrane,which is easy to block in the pores of the membrane and cause serious pollution to the ultrafiltration membrane.Simple hydraulic backwashing cannot be completely removed,so it is necessary to install a pretreatment device before the ultrafiltration to remove it,so as to ensure the long-term stable operation of the ultrafiltration.This paper mainly studies the effect of pulsed electroflocculation-electrocatalytic oxidation pretreatment technology on ultrafiltration membrane pollution caused by HA.In this study,a 50k ultrafiltration membrane were used,the effect of pulsed electrocoagulation-electrocatalytic oxidation pretreatment on the removal of humic acid was studied.The change of membrane flux and membrane resistance after the remaining sewage is ultrafiltered,with UV₂₅₄,TOC,three-dimensional fluorescence spectrum,membrane flux and other detection indicators,are used to detect the changes of membrane filtration performance before and after pretreatment,and the mechanism of mitigating membrane pollution was analyzed through characterization analysis methods such as membrane flux,membrane resistance,membrane pollution model changes and scanning electron microscope.The experiment found that pulsed electrocoagulation-electrocatalytic oxidation has a significant removal effect on HA.Pulsed electrocoagulation can remove more than 90%of HA at pH=7.Electrocatalytic oxidation also has a high removal effect on the remaining HA,and the total removal rate has exceeds to 96%,under the condition of constant current,the voltage of conventional electrocoagulation has a tendency to increase after a long period of operation and the voltage ofpulsed electrocoagulation are relatively stable.Three-dimensional fluorescence spectroscopy found that pulsed electrocoagulation preferentially removes macromolecular humic acid,and after the electrocatalytic oxidation,the peak Obviously move,the pollutants are oxidized and decomposed into intermediate small molecule compounds.Therefore,pulsed electro-flocculation-electrocatalytic oxidation has a good removal effect on HA.After pulse electrocoagulation-electrocatalytic oxidation pretreatment,as the initial pH increases,the membrane flux increases and then decreases.The electrocoagulation of the iron electrode and the aluminum electrode has a better effect on the removal in neutral conditions,and the electrocatalytic oxidation has a strong oxidizing ability to the remaining HA,which can further remove HA and alleviate membrane pollution.Aluminum electrode pulsed electro-flocculation-electrocatalytic oxidation has lower removal rate of HA at initial pH=3 and 11,and higher removal rate at pH=5,7,9;iron electrode pulsed electro-flocculation-electrocatalytic oxidation removal of HA The rate has little correlation with pH.Invesgiating the indicators of membrane flux and membrane resistance,it was found that pulsed electrocoagulation-electrocatalytic oxidation significantly reduced membrane pollution by removing HA.The aluminum electrode produced less floc in the initial pH=3and11,and had an poor effect on HA removal,which leads to a high correlation coefficient between the middle blockage and the filter cake layer.The pollutants block the pores of the membrane and accumulate to form a filter cake layer.SEM showed that a thinner and more viscous filter cake layer was produced on the membrane surface,resulting in obvious membrane pollution.Under the initial pH=9and11 conditions,the iron electrode produced flocs with small and dispersed particles,which were difficult to settle when suspended in the solution,resulting in high clogging and clogging in the filter cake layer.