Microbial structure and its control method for upgrading MBR

点击翻译按钮获取中文摘要

This study aimed to clarify the controlling factor for upgrading membrane bioreactor (MBR) based on the microbial community analysis in the MBR. The main results obtained are as follows. The MBR experiments were conducted using real wastewater of sewage treatment influent. It was revealed that bacterial group of gamma Proteobacteria, especially Xantbomonas sp having a high potential of producing biopolymer, were selectively grown on the membrane surface, which were different from the predominat bacterial groups in the mixed liquor suspended solids, even though the MBR was operated under low organic loading conditions. This suggests that the polymer producing Xanthomonas sp might give a trigger of membrane biofouling. Simulation results on floc formation in MBR considering a predation pressure of higher tropic level of microorganisms showed that the shape of flocs changed from sphere to flat under a high predation pressure. i.e., the length of the two-dimensionally projected flocs became longer. This suggests that higher tropic level of microorganisms have a certain role to control the small flocs in MBR. In addition, a new numerical calculation method was applied to simulate the mass transfer into biological file (cake layer) on the membrane surface. By applying Coriolus versicolor, a highly -functional microorganisms, to the treatment of dye-wastewater in MBR showed that a very high performance of removing the dye-color was easily obtained. As for sludge reduction potential of metazoan in MBR, 1,000 to 2,000 number per mL of metazoan gave no significant difference in sludge reduction. However, when a lot of earthworms were attached to the membrane surface, the attached biomass was reduced. This means metazoan was effectively used to control the membrane fouling. Therefore, it is possible to develop a ecological control method against the membrane fouling.