| In practical applications of membrane bioreactor,membrane fouling has always been a problem that needs to be considered in the MBR system.The presence of membrane fouling affects membrane flux and permeability,reduces the filtration efficiency of MBR,and ultimately leads to higher operating costs due to the need to clean the membrane.The combination of membrane bioreactor and microbial fuel cell(MFC)to improve the effluent quality and reduce membrane pollution has achieved good results.In this coupled reactor,although the power output is not high,it slows down the membrane fouling in the MBR.Microbial fuel cell(MFC)is a new process that can generate clean electricity without energy input.It is added to the MBR based on the internal micro-electric field generated by MFC to form an MFC-MBR coupling process to achieve energy recovery from sewage.Improve system processing efficiency and suppress membrane fouling,etc.In order to find a method that can recover the energy utilization of MFC and further strengthen the suppression of MBR membrane fouling,this study was modified on the basis of the MFC-MBR coupling system.The membrane module was inserted in the cathode chamber of the MFC,and the membrane module was inserted in the middle.The carbon felt electrode,as the cathode of the MFC,is placed around the periphery of the MFC cathode chamber,and the carbon felt is connected to the anode of the MFC.A circular electric field formed by the carbon felt electrode in the center of the MBR membrane module and the surrounding carbon felt was used to study the mechanism of membrane fouling suppression under the action of the circular electric field.At the same time,the MFC-MBR coupling system was used as a control group for experimental operation.In this study,16 S rRNA gene high-throughput technology was used to compare and analyze the microbial community structure in the four positions of the cathode chamber sediment,suspension,MBR membrane surface and membrane filaments in the two coupled systems after the membrane fouling cycle.Regular sampling is performed on the surface and the electric field to clarify the type and quantity of microbial flora on the membrane surface and the electric field,analyze and reason about the adhesion and desorption process of microorganisms on the membrane surface in the coupling system,and then reveal the mechanism of mitigating membrane fouling.The main achievements are as follows:(1).Using glucose as the sole carbon source under the starting conditions of MFC,the voltage output of the operating system was finally stable after 28 days,and the two MFC systems were successfully started and domesticated.After the successful domestication of the MFC and the stable power generation,the device was modified and the experiment began to run.Compared with the MFC-MBR coupling system,the COD removal rate of the anode chamber in the annular electric field MFC-MBR coupling system is increased by 4.7%,and the MBR effluent removal rate in the cathode chamber is increased by 2.8%.The removal rate of ammonia nitrogen in the anode chamber of the annular electric field MFC-MBR coupling system is increased by 0.7% compared with that of the MFC-MBR coupling system,and the removal rate of ammonia nitrogen in the MBR effluent water is increased by 13%.The circular electric field not only strengthens the processing effect of the coupling system,but also makes the biological processing efficiency of the coupling system more stable.(2).The circular electric field has a certain selective effect on the ecosystem of the microbial flora in the coupling system,mainly for the structure of the microbial flora in the MBR membrane module.The microbial flora of the samples at the two positions of the bottom mud and the suspension did not change significantly,and the structure was roughly similar.In the phylum classification level,the circular electric field has a greater inhibitory effect on the growth of the two dominant bacterial groups,Proteobacteria and Bacteroidetes.These two flora can promote the formation of biofilm and the stability of the structure.At the level of genus classification,Zoogloea,Acinetobacter and Acidovorax have different effects on the formation of biofilm and the stability of its structure.The relative abundance ratios of Zoogloea and Acinetobacter in the MBR membrane surface and membrane filament samples in the ring electric field coupling system have decreased.The ring electric field inhibits the growth and reproduction of these two bacterial groups,thus reducing the structure and density of the biofilm.Thereby slowing down the degree of clogging of the membrane pores.(3).The membrane fouling cycle of the ring-shaped electric field MFC-MBR coupling system is 17 days,and the membrane fouling cycle of the MFC-MBR coupling system only needs 10 days.The circular electric field prolongs the membrane fouling cycle time in the MFC-MBR coupling system,and effectively alleviates the membrane fouling in the MFC-MBR system.Scanning electron microscopy observed the growth morphology of the MBR membrane surface in the two coupled systems after membrane fouling.The results showed that compared with the control group,the MBR membrane sample under the circular electric field improved the microbial flora structure in the coupled system and reduced the bacteria.Group secretions,which increases the flux of MBR and slows down the rate of membrane fouling.The Zeta potential(absolute value)of the sludge mixture in the cathode chamber in the ring-shaped electric field MFC-MBR coupling system has been on a downward trend,from 10.9m V to 5.3m V.The Zeta potential of the MFC-MBR coupling system rises from 7.5m V to 14.2m V during operation.The annular electric field makes the substances in the surrounding environment of the MBR membrane module easy to condense into large clusters of flocs,thereby enhancing the sedimentation performance,and is not easy to be attracted by the membrane,which leads to more serious membrane pollution. |
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