Study On AFMBR Treatment Efficiency Of Domestic Sewage Enhanced By Composite Particles And Membrane Fouling Control

With the growth of Chinese population and the acceleration of urbanization,domestic sewage has become the main source of new sewage discharge.Meanwhile,treatment resource consumption is huge,and its energy consumption accounts for about 1%of the total electricity consumption of the whole society.Therefore,according to the water quality characteristics of domestic sewage,an efficient and low energy consumption treatment technology is sought,which can realize the resource recovery,reduce the pressure of energy shortage,reduce the environmental pollution caused by sewage discharge,and alleviate the water crisis.This paper constructed an integrated anaerobic fluidized bed membrane bioreactor to treat domestic sewage and studied the research of MGAC composite particles to strengthen AFMBR treatment efficiency and alleviate membrane pollution.AFMBR was successfully started in 62 days at 35℃,HRT was 21 h and the influent p H was 7.4-7.6.During the whole start-up process,the reactor had no acidification phenomenon and had good operating efficiency.At the end of startup,the t COD concentration of the AFMBR effluent was 51 mg/L,and the removal rate was 68.7%.GAC could enhanced the t COD removal rate by 5.3%and MGAC could enhancde the t COD removal rate by 6.1%.During the entire startup process,the three reactors effluent SS concentration（less than 7 mg/L）could reach the SS standard of effluent grade A in"GB 18918-2002".At the same time,in start-up stage the sludge zeta potential of-8.7 m V,the average particle size of sludge volume of 22.079μm,the polysaccharide contents of 30.42 mg/g VSS,protein content of 63.81 mg/g VSS in sludge EPS were decreased by MGAC.On the basis of ensuring the treatment efficiency,the reduction of HRT could improve the treatment volume and efficiency of sewage.When HRT was greater than or equal to 4 hours,the effluent t COD of each reactor could achieve good removal efficiency.The average t COD removal rate in the AFMBR reactor was 83.29%,GAC increased the average t COD removal rate by 1.46%,MGAC increased the average t COD removal rate by 7.28%.The reduction of HRT did not change the structure of anaerobic sludge,but decreased the volume average particle size of sludge.When HRT decreased from 21 h to 4 h,AFMBR volume average particle size decreased by49.38%.The average particle size of GAC-AFMBR decreased by 45.51%.The average particle size of MGAC-AFMBR decreased by 54.69%.In terms of membrane fouling,the reduction of HRT could increase the transmembrane pressure difference in the reactor.According to the microbial community results of membrane samples and sludge samples during the start-up period,MGAC composite particles could increase the abundance of bacteria on membrane surface,reduce the diversity of the membrane surface community and the abundance and diversity of the community in the sludge.GAC could reduce the relative abundance of Firmicutes on membrane surface by27.6%,increased the abundance ratio of Skermanella on the membrane surface,and increased the abundance ratio of Longilinea bacteria in the sludge to alleviate membrane pollution.MGAC could reduce the relative abundance of Firmicutes bacteria on membrane surface by 30.04%,increased the abundance ratios of norank＿f＿anaerolineaceae and unclassified＿k＿norank＿d＿Bacteria in membrane surface and sludge to enhance anaerobic microbial hydrolysis and alleviate membrane contamination to slow down membrane fouling.In the analysis of archaea community,GAC and MGAC reduce membrane pollution by reducing the abundance of Halobacterota species,the abundance proportion of Methanolinea,the abundance of Norank＿f＿＿norank＿o＿＿norank＿c＿＿Bathyarchaeia filamentous bacteria,and Methan osaeta filaments.MGAC was stronger than GAC.Membrane surface in EPS of 1.77 mg/cm² polysaccharide content and 24.1mg/cm² protein content were decreased by MGAC to mitigate membrane fouling.When HRT is 4 hours,the growth rate of TMP was higher in MGAC-AFMBR（0.0024MPa/d）than in AFMBR（0.0018 MPa/d）than in GAC-AFMBR（0.0015 MPa/d）,and the shortest time of MGAC-AFMBR was 13 days.MGAC could reduce protein content and polysaccharide content on membrane surface to alleviate biological con tamination.However,the MGAC hydrolyzed Fe³⁺would adsorb on the membrane surface and had a complex reaction with the filter cake layer on the membrane surface,which would aggravate the inorganic pollution on the membrane surface.