The widespread application of membrane bioreactors(MBRs)is limited by membrane fouling,and the adoption of effective control methods is crucial.The microbial fuel cell(MFC)is coupled with the MBR,and the micro-electric field generated by the MFC is used to control the membrane fouling of the MBR.At the same time,the wastewater treatment performance of the MFC is improved.However,aeration is a necessary condition for the operation of the system,and the membrane fouling situation under the coexistence of microelectric field need to be further explored.In view of the above problems,a ring-shaped MFCMBR coupling system is constructed in this study.The effects of aeration and micro-electric field on membrane fouling were studied,and the mitigation mechanism of membrane fouling was analyzed through the changes in the properties of the mixed liquid sludge and the membrane surface.During the start-up and operation of the MFC-MBR coupling system,the voltage maintained a relatively stable continuous output state after two months of the inoculation and acclimation,it shows that the reactor is successfully started.Then the MFC and MBR are coupled.When the hydraulic retention time(HRT)is 36 h,the effluent chemical oxygen demand(COD)concentration of the MFC-MBR coupling system is significantly reduced,and the COD removal rate is all above 94%,the system can stably operate stably for a long time.The effects of aeration and micro-electric fields on membrane fouling are analyzed.The membrane fouling rate of the MFC-MBR coupled system was 34%,35%and 8%lower than the C-MBR control system.It demonstrates that the application of micro-electric field is beneficial to the mitigation of membrane fouling.When the aeration intensity is low,the cake layer resistance of the MFC-MBR coupling system decreased by 30.7%and 26.7%.But when the aeration intensity is 2.5 L/min,the cake layer resistance of the MFC-MBR coupling system decreased 13.2%.This may be due to the interference of high aeration,the mitigation of the foulants of the cake layer by the micro-electric field is weakened.At the same time,since the cake layer resistance contributes more to the total resistance,and the membrane pore resistance is mainly affected by the aeration intensity,the decrease in the membrane fouling rate under high aeration may be mainly due to the mitigation of the cake layer fouling is weakened.Combined with the treatment performance of the system,when the aeration intensity is 1.5 L/min,the improvement effect of COD removal rate is the best(5.8%),and this working condition is the best operating condition of the system.Membrane fouling characteristics of MFC-MBR coupling system are studied.The time required for the MFC-MBR coupling system to reach 25 kPa is extended by 16 days,the foulants are less and more loosely attached to the membrane,indicating that the membrane fouling is effectively alleviated.The polysaccharides,proteins and inorganic elements on the membrane surface is reduced in the MFC-MBR coupled system,indicates that the effect of the micro-electric field reduces the adhesion of foulants on the membrane surface.Compared with the C-MBR control system,the SMP and LB-EPS in the sludge mixed liquor of the MFC-MBR coupled system decreased,which may be caused by electrostatic repulsion,electric neutralization,and microbial degradation.At the same time,the content of protein and polysaccharide in LB-EPS decreased by 38.5%and 50.1%,respectively.The large reduction of polysaccharide makes it less adhesive on the biogel layer,it is also the reason why the membrane fouling of the MFC-MBR coupling system is alleviated.The reduction of negatively charged groups near the membrane module leads to a decrease in the absolute value of zeta potential,the repulsive force between sludge particles also decreases,and the flocculation of sludge is improved.In addition,TB-EPS increased under the induction of micro-electric field,and the increase of TB-EPS also produced more stable sludge flocs.Due to the increase of sludge flocculation,the average particle size of the MFC-MBR coupling system became larger,and the proportion of small particles in the mixed liquid decreased.This resulted in the decline rate of membrane flux is slower,and the membrane fouling of the MFC-MBR coupling system was alleviated. |