Enhanced Mitigation Of Ultrafiltration Membrane Fouling By The Regulation Of Floc Morphology And Electric Field Effect In Electrocoagulation

Ultrafiltration?UF?technology is one of the most promising and attractive techniques in both drinking water treatment and waste water reclamation.However,membrane fouling is a major impediment to broader application of membrane technology.Thus,new hybrid technology should be explored to improve membrane performance after regulating and controlling the effect between membrane surface and flocs/particles.Comparative study on pretreatment process of ultrafiltration:chemical coagulation?CC?and electrocoagulation?EC?.The results showed that taking the EC as a pretreatment,the flocs were more strong and compact,the cake layer deposited on the surface was porous and high hydrophilic;while taking CC as a pretreatment,the flocs were loose and had low strength,which would be compacted and crushed easily by the pressure in membrane filtration process,resulting in relatively dense cake layer and low hydrophilic.Therefore,EC is the most effective pretreatment process to alleviate membrane fouling during operation,which can maintain a flux that is about 5.57%higher than CC.Study the performance of EC-UF with EC as the pretreatment process of UF.The results showed that the EC-UF technology can mitigate the membrane fouling effectively,and the key to mitigate the membrane fouling by EC is to form a loose and porous cake layer on the membrane surface.Increasing the current density,and water quality conditions at neutral pH,the EC-UF technology would maintain a higher flux.On the conditions that current density,initial pH,initial conductivity,electrolysis time and humic acid?HA?concentration were 10 A·m^-2,7,1000?S·cm^-1,15 min,10 mg·L^-1 respectively,the HA removal rate could reach at 97.3%.This membrane fouling was reversible and cleaned membrane flux could be recovered to 94%of the initial flux.Electric field has effect on mitigating membrane fouling.Hence,a novel electrocoagulation membrane reactor?ECMR?was investigated in this paper,which embraces EC,UF,and electric field,all in one individual reactor by arranging the membrane module between the anode-cathode electrodes.Results indicated that increasing the current density the ECMR process could maintain a higher flux;and the electric field also shown an important effect on cake layer that was formed of the polarized charged flocs,which make the cake layer was more porous,hydrophilic and stabilized with the increasing of electric field intensity.When the electric field intensity increased from 0 V·cm^-1 up to 10V·cm^-1,the normalized specific flux of ECMR improved from 72.3%to 90.4%at 30 min.Compare to membrane filtration,the ECMR greatly alleviate membrane fouling and improve the quality of permeate during operation,and the normalized specific flux and HA removal rate for ECMR were about 35.1%and 39.7%higher than UF at 30 min,respectively.