Formation of sub-visible micro-particles in the supernatant of AnMBRs under sulfate stress and their fouling behavior on membrane
Anaerobic biological treatment of sulfate wastewater has been a research hotspot,but less attention has been paid to the effect of sulfate on the properties of sludge mixture,the micro-particles composition of supernatant and their correlations with membrane fouling behavior.In this study,three identical AnMBRs were set up and operated at different COD/SO42-ratios of＞10,2.5 and 0.5 for over 200 days,respectively,to reveal the effects of different COD/SO42-ratios on the performance of AnMBR system,the formation of sub-visible micro-particles(0.45～10 μm)in the supernatant and their fouling behavior.The results showed that the COD concentration in the supernatant increased significantly with the decrease of COD/SO42-ratios;at COD/SO42-ratio of 0.5,the COD value of supernatant increased to 4 000 mg·L-1,and the ratio of H2S was up to 1.6％,and the methanogens were severely inhibited.Accordingly,the growth rate of the transmembrane pressure(TMP)increased significantly under high sulfate stress.The dead-end filtration test indicated that at the identical TSS concentration,the sludge mixed solution of AnMBRs showed the worst filterability and the membrane filtration behavior of the supernatant was almost identical with the sludge mixed solution.In addition,at the same COD concentration,the filtration rate of the supernatant was the slowest for the high sulfate stress group,and the membrane resistance was the highest,where the percentage of cake layer fouling resistance was over 95％.Furthermore,the concentration of micro-particles(0.45～10 μm)in the supernatant under high sulfate stress increased distinctly(the percentage of＜10 pm particles being 75％～80％).More importantly,the proportion of particles in the range of 0.45～5 μm in the cake layer of membrane surface was higher than that in the supernatant,indicating that these micro-particles in the supernatant had a higher accumulation potential on the membrane.Overall,our work could provide some theoretical basis for understandings and further control of membrane fouling in AnMBRs.
万方数据
维普
