Microbial structure and its control method for upgrading MBR

本研究旨在通过对膜生物反应器(MBR)中微生物群落的分析，明确MBR升级改造的控制因素。取得的主要结果如下。采用污水处理进水的实际废水进行了膜生物反应器试验。结果表明，尽管膜生物反应器在低有机负荷条件下运行，但与混合液悬浮固体中的优势菌群不同的是，在膜表面选择性地生长着伽马变形杆菌，尤其是产生物潜力较大的Xantomonas sp。这表明，产生黄单胞菌的聚合物可能是膜生物污染的触发因素。对MBR中絮体形成的模拟结果表明，在较高的捕食压力下，絮体的形状由球形变为扁平。即，二维投射的絮体的长度变得更长。说明较高的趋向性微生物对MBR中的小絮体有一定的控制作用。此外，采用一种新的数值计算方法对膜表面生物膜(滤饼层)的传质过程进行了模拟。将一种高效微生物杂色云芝应用于膜生物反应器中染料废水的处理，结果表明，该菌对染料色度的去除效果很好。对于膜生物反应器中后生动物的污泥减量潜力，每毫升投加1,000至2,000个后生动物对污泥减量没有显著影响。然而，当大量的蚯蚓附着在膜表面时，附着的生物量减少。这意味着后生动物可以有效地控制膜污染。因此，开发一种针对膜污染的生态控制方法是可能的。

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.