Fouling Suppression And Operation Effect In A Ceramic MBR By Using Low-Voltage Electric Field

Membrane bioreactor has attracted much more attention owing to its own advantages,such as compact configuration,stable treatment efficiency,low sludge yield and high automation.However,membrane fouling and its resulted in loss of the membrane flux,the decreasing of its lifespan,and the increasing of operation cost,highly constrained MBR widespread development and application.In this study,a physical method,i.e.external low-votage electric field,was used to control membrane fouling in a ceramic MBR,which did not require additional chemicals dosage and without second pollution.The membrane fouling alleviated by the electric field mainly due to the the repulsive charge between sludge particles or colloids with membrane surface,by which the foulants could be drived away from the membrane surface.Thus,these foulnats accumulation on the membrane surface could be minimized.Three ceramic MBRs(CMBRs)with varied cathodes,including Fe,Ti and Cu,were assembled in parallel to evaluate their fouling control and pollutants removal efficiency,with an intermittent electric with a 2.5 A/m2 electric current.A traditional ceramic membrane MBR was carried out under the same conditions as a control reactor.In order to analyze the membrane fouling control mechanism by the applied electric field,the removal rate of pollutants by MBRs,and the the influence of the electric field and electrocoagulation on the membrane fouling and mixed liquor characteristics were comparatively researched.Compared with C/Ti-MBR,C/Cu-MBR,as well as the traditional MBR,Fe/Ti-MBR had a lower transmembrane pressure increase rate and a higher pollutants removal rate.This was caused by the induced flocculation in the system that was evidencd by the higher sludge size and lower zeta potential within Fe/TiMBR.The formed membrane fouling was more easily to be detached by simple backwashing in all electric MBR,regardless of the cathode materials adopted,since that there were significant electric repulsive force to prevent foulants deposition.In addition,the content of soluble microbial products(SMP)in t he applied field MBR had a significant positive correlation with the extent of fouling,indicating that the lower SMP in Fe/Ti-MBR can also alleviate membrane fouling.It was illustrated that the combined effect of electric field force and electrocoagulation induced by iron release in the electric field was the main reason for membrane fouling alleviating in Fe/Ti-MBR.According to the comprehensive energy consumption analysis,the system showed that the electric energy consumption of Fe/Ti-MBRwas increased only around 12.22%,which contributed to 38.1% reduction of membrane fouling.The external resist was used to replace the external power supplier,and the MBR was transformed into a biological electrochemical reactor(E-MBR)where the system electricity was generated in-situ.A long term filtration experiments showed that the COD and NH4+-N in the effluent of E-MBR system were 22 mg/L and 2.7 mg/L,respectively,while the membrane fouling rate of E-MBR was about 25.6% lower than the MBR.Moreover,the concentrations of SMP and EPS in EMBR sludge mixture were lower that those in MBR,which could also effectively reduce the migration and attachment of contaminants to the membrane surface,and then to eventually minimize membrane fouling.Therefore,it was deduced that E-MBR could in-situ utilize the power generated from the biodegradation of organic substances in watewater which to effectively control membrane fouling,which have very limited influence to the pollutants treatment efficiencies.