| With the rapid growth of economy and the realization of a higher level of urbanization,the amount of domestic sewage discharged in urban and rural areas has increased significantly,and the demand for domestic sewage treatment is also growing.At present,the conventional domestic sewage treatment mostly adopts aerobic process,which has the defects of large energy consumption and failure to utilize the resources in the sewage effectively.Anaerobic membrane bioreactor,however,can effectively achieve the separation of mud and water,degradation of organics with a small cover of area and low energy consumption,and recovery of energy.However,membrane fouling reduces the efficiency of anaerobic membrane bioreactor and restricts its development in the field of wastewater treatment.In a fluidized bed,membrane fouling can be effectively reduced due to the scouring effect of particles on the membrane.Therefore,this paper aims to explore the effective strategy of membrane pollution control in anaerobic membrane process,the main research contents are as follows:Experimental material was prepared and characterized.At the same time,the acclimation of anaerobic granular sludge as well as the design and start-up of AFMBR were completed.Compared with GAC,MGAC prepared by the co-precipitation method has a rougher surface,smaller pore size and uniform distribution.The contact angle of MGAC is 35.9% lower than GAC,which indicates better hydrophilicity.After three stages of acclimation,the COD removal rate of the reactor reached 68.9%,with the COD concentration of the effluent below 80 mg/L.The ORP was lower than-510 m V and the p H of the effluent was between 6.9 and 7.3.The methane and carbon dioxide accounted for 35% and1.8% of the total gas respectively.A further test showed that the optimum height diameter ratio of AFMBR was 10 while the optimal reflux rate of it was 40 m L/min.The operation efficiency and membrane fouling condition of AFMBR were analyzed.In terms of pollutant removal efficiency,the AFMBR with magneticparticles performed better,the average COD concentration of effluent was 77.4mg/L,and the removal rate was 57.1%.The conductivity of effluent from AFMBR with magnetic particles showed a greater decrease of 16.9 %.There was no significant difference in the concentration of volatile acids and p H.The effect of nitrogen and phosphorus removal was not significant as well.In terms of membrane fouling,the increasing rate of transmembrane pressure of reactor with MGAC was slower(0.52 k Pa/d).After an operation of 28 days,the flux of membrane in reactors with GAC and MGAC decreased by 36.4 % and 11.2 %respectively.The results of SEM showed that the pores of the membrane from reactor with GAC were seriously blocked,while the pollutant density on the surface of membrane from reactor with MGAC was relatively low.The microbial community in the reactors was analyzed,and the control strategy of membrane fouling was put forward.The abundance of microbial community in reactor with GAC was higher than that in reactor with MGAC,and the diversity of bacterial community was also higher.However,the reactor with MGAC showed a higher diversity of archaea.In terms of bacterial community,Proteobacteria(33.01 %)and Chlorofloxi(16.89 %)were dominant in reactor with GAC,while in reactor with MGAC,Firmicutes(44.66 %)and Bacteroidetes(37.52 %)were dominant.In terms of archaea community,Methanothrix(89.61 %)was dominant in reactor with GAC,while the dominant archaea in reactor with MGAC was Nitrososphaera(50.04 %).Electric field and intermediates were found to be helpful in restraining membrane fouling,so it is considered to run AFMBR in the weak electric field,and select the appropriate size,dosage ratio and renewal rate of the intermediates to prolong the service life of the membrane. |
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