Effect Of Microbial Community Structure On SFDMBR Performance And Membrane Evolution

Self-forming Dynamic Membrane Bioreactor (SFDMBR) which couples a non-woven fabric, nylon mesh or a filter-cloth membrane with a bioreactor, has replaces conventional micro filtration/ultrafiltration membranes as filtriation modules. It uses formed Self-forming Dynamic Membrane (SFDM) deposited on the mesh materials by active sludge in the intinal separation process, to acquire approximately separate results of conventional membranes. Membrane fouling was the principal factor to restrain the SFDMBR development and application. The formation of dynamic membrane fouling was complicated and, was a combined process of microbial and their metabolites. In order to analyze the interaction of them, a concept of dynamic process should be introduced. The paper analyzed microbial physiology and ecology characteristics to study the relationship between microbial community structure and SFDMBR performance also with the microbial metabolic products to offer theory evidence for SFDMBR performance and membrane fouling controlling.This study used self-forming submerged membrane bioreactor (SFDMBR) for synthetic wastewater treatment. A non-woven fabric membranes module was immersed in the tank. At the full stage of membrane filtration, the extraction of microbial metabolites in activated sludge(AS), and dynamic membrane(DM) biofilm under different evolution stages of DM/aeration, combined with the community structure analysis, to analyze the correlation of membrane fouling, microbial and their metabolites.The conclusion stated that the relationship was not obvious between the total bacterial community changes and the reactor operation effect under the different stages of DM. The diversity of the microbiology community with DM3was below that with DM1and DM2, but the COD average removal rate was always above90%.We found some micro-organisms were related to the production of EPS by analyzing the relationship between microbial community structure and EPS. On the DM3surface, the release quantity of EPS was higher than DM1&DM2. There were some special micro-organisms existing under the conditions, and the bacteria had some denitrifying function. Thus, we perfume some denitrifying bacteria would make more EPS to affect the membrane fouling.The conclusion stated that the COD and NH3-N removal of SFDMBR was not influenced by aeration, average removal rate was always above90%.According to the analysis of microbial community under different aeration, AS had a similar community, while the diversity of the DM biofilm community was much higher. Aeration had a great affect with the DM community, for low flux lead to a stronger collective enrichment and a larger diversity. The research on metabolites revealed that high aeration had higher produce of EPS. This phenomenon was similar with AS. The metabolites of DM followed the same rule under different aeration, the protein was higher than polysaccharide.According the study of DM evolution, this paper offered three assumptions.One was that the microbial community was different beween sluge mixed liquor and membrane surface, and dominant micro-organisms in sluge was not the main reason for membrane fouling. Also we found some special micro-organisms existed on the membrane because they were fed on the substance on membrane surface, and they had a common role with the micro-organisms attached on the membrane which produced more EPS to cause the membrane fouling. Aeration intensity have a significant effect on microbial community structure of the self-forming dynamic membrane, but has little effect on microbial community structure in activated sludge.