Biodiversity And Succession Of Microbial Community In An Integrated A/O Membrane Bioreactor

Membrane bioreactor is a new type wastewater treatment reactor which combines membrane separation technique with biotreatment technology. For the advatages of long SRT, less excess sludge and good water quality, it becames a hotspot in the field of wastewater treatment and water reuse. Biological activity of activated sludge in MBR mainly depends on microbial community’s structure and function. The richer flora’s diversity is, the stronger system’s stability will be. This study to build an integrated A/O membrane bioreactor as the starting point, strive to achieve coexistence of multi-habitat in an membrane bioreactor, which will render the diversity of microbial community more richer. The reactor can obtain good performance with smaller footprint and less power consumption.In the experiment, a self-designed intergrated A/O MBR was used as testing apparatus, which was automatic controlled by programmable logic controller. The reactor was continuous operating for100days without any sludge discharged, the biomass concentration in reactor accumulated from4000mg/L to14000mg/L. During the whole operation, two dissolved oxygen meter installed in two zones of reactor for real-time, continuous and synchronous monitoring dissolved oxygen. The monitor result showed that in the fifth day of operation, dissolved oxygen of anoxic zone decreased to less than0.2mg/L, meanwhile, dissolved oxygen of oxic zone was about3.6mg/L. This indicated the formation of anoxic condition and oxic condition, the integrated A/O MBR was constructed successfully.In the experiment, conventional measuring method, polymerase chain reaction-degeneration gradient gel electrophoresis and cloning sequencing technology were combined to monitor running condition of system. Test results of conventional index showed, the removal rate of COD, NH4+-N and TP remained at a high level, among them the removal rate of COD and NH4+-N increased as time went on, while the TP declined. Test results of PCR-DGGE showed that from stage S to stage5, biodiversity and similarity between anoxic zone and oxic zone showed succession regulations in two sides:the same area of different stages and the same stage of different areas. Cloning sequencing results showed dominant bacteria strains in the system mainly contained6groups:Proteobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, Firmicutes and Acidobacteria. Thereinto, Proteobacteria was the most dominant bacteria strain, which included Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. Besides, the detection results also displayed that Methylibium sp. was denitrification bacteria; Acidobacteria was dephosphorization bacteria; Leptothrix sp. and Sphaerotilus sp. were two kinds of filamentous bacteria; Chloroflexi was obligate or facultative photosynthetic filamentous bacteria.