Study On Characteristics And Mechanism Of MBR Membrane Fouling In Upflow Micro-oxygen Reactor

Membrane bioreactor(MBR)can cause membrane fouling due to factors such as the nature of the membrane,operating conditions,and characteristics of the mixture.The SNAD process refers to a simultaneous reaction of short-range nitrification-anaerobic ammonium oxidation-denitrification under micro-oxygen conditions.In order to further understand the cause of the membrane fouling in the SNAD process and the mechanism,this topic is to artificially prepare the simulated C/N=1 industrial wastewater,and study the physical and chemical process in the membrane bioreactor with the sludge physicochemical Changes in properties,and the causes of membrane fouling under different membrane fluxes and the effect of the mixture on membrane fouling.(1)In this experiment,as the activity and concentration of anaerobic ammonium oxidizing bacteria in SNAD gradually increase,the effluent of the reactor is kept good by controlling the parameters such as dissolved oxygen and alkalinity in the reactor,and the effluent ammonia nitrogen,sub-The average values of nitrate,nitrate and COD were 14 mg/L,10 mg/L,10 mg/L and 15 mg/L respectively;the removal rates of ammonia nitrogen,total nitrogen and COD could reach 90%,85%and 90%,respectively;The device has a good decarburization and nitrogen removal effect during operation.(2)During operation,the sludge concentration increased from 15.5 g/L to 16.8 g/L,and the MLVSS/MLSS ratio was 0.7-0.75.The sludge particle size increased with the increase of running time,and the average particle size d(0.5)From 67.956 ?m to 161.739 ?m,the sludge performance is good.(3)Contaminant analysis under the conditions of membrane fluxes of 2.5 LMH,5.0 LMH,7.5 LMH and 10.0 LMH,respectively,found that the content of protein and polysaccharide in EPS is much higher than that in SMP,under 2.5LMH conditions,SMP and The concentration of protein and polysaccharide in EPS is the highest.As the membrane flux increased,the concentrations of protein,polysaccharide and TOC in SMP and EPS decreased,and the analysis was considered to be related to membrane retention.(4)PN/PS is an important indicator of membrane fouling,and when the ratio increases,membrane fouling accelerates.With the increase of membrane flux,the average ratios in SMP are 0.5,0.61,0.72,and 0.92,respectively.The average ratios in EPS are 2.7,3.0,3.1,and 3.3,respectively.It can be seen that the PN/PS ratio increases significantly.Three-dimensional fluorescence analysis revealed that SMP contains tryptophan and tryptophan,and polycarboxylate-type humic acid,both of which belong to tyrosine;and EPS contains fluorescent-like protein(tryptophan protein).And tryptophan),polysaccharides,fulvic acid,humic acid.The change in membrane flux has little effect on the composition of the contaminants,but has a certain effect on the fluorescence intensity.(5)By analyzing the membrane fouling rate and observing the membrane fouling cycle,the larger the membrane flux,the shorter the membrane fouling cycle.Through data analysis,it was found that the membrane fouling period was the longest when the membrane flux was 2.5 LMH.At this time,the contribution of gel layer and cake layer to membrane fouling was higher,37%and 41%,respectively.At 5.0 LMH,both The proportion is 40%and 38%respectively.When the membrane flux is 10.0 LMH,the membrane fouling cycle time is the shortest,the membrane fouling rate is the highest at each stage,and the pore plugging effect is the most obvious 27%.(6)By using SPSS software to analyze the effect of mixture characteristics(SMP,EPS,relative hydrophobicity RH,Zeta potential,viscosity)on membrane fouling,the correlation coefficient analysis found that PN/PS>hydrophobic RH in EPS>SMP>Zeta potential>PN/PS>SMP>mixture viscosity in EPS,wherein the correlation coefficient of EPS is rp=0.927.However,EPS will interact with other factors in the mixture,and membrane fouling is a complex process.