Effect And Mechanism Of Adding Fillers On MBR Membrane Fouling

With the advantages of small footprint and low residual sludge production,membrane bioreactor(MBR)treatment technology has good effluent effect in the treatment of municipal wastewater and industrial wastewater,so it is favored by the market.However,membrane fouling(especially membrane bio-fouling)has still become a bottleneck restricting the development of MBR.Studies have shown that the main pollutants in the biofilm formation process are EPS and SMP,and the microbial quorum sensing plays a facilitating role in the biofilm formation process.In recent years,despite the continuous improvement and development of membrane fouling control measures,the mechanism for delaying membrane fouling lacks detailed studies.Therefore,it is necessary to systematically relate the MBR operating conditions,the level of AHL type signal molecules,the composition and function of microbial communities,the secretion and characteristics of EPS,and the degree of membrane fouling,and determine the effect of membrane fouling control measures on retarding membrane fouling under operating conditions and the mechanism of action.In this study,the formation and composition of membrane bio-contaminants were first analyzed.Two groups of identical membrane bioreactors were first run to analyze membrane biological contaminants.Membrane fouling was controlled from the reactor configuration.Two sets of MBR reactors were run at the same time,one set of conventional membrane modules was added,and the other set was filled with hollow packing pellets around the membrane modules.During the operation process,the sludge mixture and the biofilter of the two reactors were sampled by combining the changes in transmembrane pressure.The changes in the components of EPS and SMP were detected,and the AHLs signal molecules were extracted at the corresponding sampling time.The microbial community structure in different membrane fouling stages was analyzed.The results show that the pollutants in EPS are mainly proteins,while the main pollutants in SMP are polysaccharides.The EPS and SMP in the biofilm are mainly derived from the EPS and SMP in the mixture.The main components of the mixture and biofilm are EPS,indicating that EPS is the main pollutant causing membrane fouling.Protein plays an important role in the process of membrane fouling.In the study of the effect of fillers on the membrane fouling performance of MBR,the results show that the addition of fillers can increase the adsorption area of microorganisms and pollutants in the mixed liquor.By comparing the membrane contaminant changes in the two groups of reactors,it shows that the addition of fillers can reduce the production of EPS and the secretion of proteins by reducing the attachment of membrane biomass and contaminants in the mixed liquid on the membrane.In the study of membrane fouling control,four signal molecules are detected in the MBR1(control group)and MBR2(filler-added experimental group)mixtures and biofilters: C4-HSL,C6-HSL,3-oxo-C6-HSL and C8-HSL.In the mixture,the highest content of both reactors is 3-oxo-C6-HSL,followed by C4-HSL,and the two lowest signal molecules are C6-HSL and C8-HSL.At the initial stage of membrane fouling,the main Ferroginibacter strains in the MBR1 and MBR2 biofilters promote the polysaccharides in the biofilter EPS through the production of C4-HSL and 3-oxo-C6-HSL,and the C8-HSL produced by Ferruginibacter can also Promote the production of polysaccharides in some EPS.In the middle phase of membrane fouling,C4-HSL and C6-HSL secreted by Sphaerotilus in the MBR1 and MBR2 biofilters,C6-HSL signaling molecules produced by Terrimonas,and C4-HSL and 3-oxo-C6-HSL secreted by Ferruginibacter may promote Contaminant production,but there may be deviations in the extraction and testing data,leading to inaccurate correlation analysis and further verification.At the end of the membrane fouling,the signal molecule content is less,but there is a big difference between MBR2 and MBR1,and a small amount of C8-HSL produced by Ferruginibacter might promote the production of some proteins in MBR1.Norank_f__Anaerolineaceae and Norank_f__Neisseriaceae were present in MBR2 and may be group quenched.This indicates that the filler affects the concentration of signaling molecules by affecting the distribution of quorum sensing flora in MBR,thereby affecting the secretion of contaminants in EPS and SMP,and ultimately delaying membrane fouling.This study has comprehensively analyzed the effect and mechanism of adding fillers to retard membrane fouling in MBR,and achieved better membrane fouling control effects.