Correlation Of Microbial Metabolites And Membrane Fouling In MBR

The shortage of water resource, and more strict law about fresh water or contaminant treatment, together pulled the widely use of MBR. Membrane fouling was the main factor to restrain the MBR development and application. The formation of 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. As can determine the variation of filtration capacity, flux was an important factor affect membrane fouling, and has a great affect on the condition of microenvironment.This study used anaerobic-aerobic submerged membrane bioreactor (A/O MBR) for synthetic wastewater treatment. A polyethylene hollow fiber microfiltration membranes module was immersed in the aerobic tank. At the full stage of membrane filtration, the extraction of microbial metabolites in activated sludge(AS), cake sludge(CS) and inner biofilm(BF) under different flux was studied, combined with the community structure analysis, to analyze the correlation of membrane fouling, microbial and their metabolites.The conclusion stated that the COD and NH4-N removal of MBR was not influenced by flux, average removal rate was always above 95%. Anaerobic tank observed a higher NOx-N removal rate under low flux than high flux at 67.9% to 50.1%, and was attributed to the accumulation of microbial metabolites on membrane surface.According to the analysis of microbial community under constant flux, AS had a similar community with CS, while the diversity of the biofilm community was much higher. Flux had a great affect with the BF community, for high flux lead to a stronger collective enrichment and a larger diversity. At the beginning of each fouling stage, microbial in CS interacted a lot and influenced the AS community.The research on metabolites revealed that high flux had higher produce of biofoulants. This phenomenon was not significant for microbial had a better reverse transport under low flux. The Metabolites of CS followed the same rule under different flux, the p/c ratio in EPS increased gradually. An assumption was proposed about the impact of microbial metabolites to membrane fouling: carbohydrates was absorbed rapidly at the initial fouling, then microbial related with carbohydrates utilization was prior to deposit on the membrane surface and meanwhile extracted large amount of EPSp, so the steady-state fouling rate correlated well with EPSp and SMPc. The filtration resistance was determined by the combination of EPSp, SMPc and SMPp. At the stage of cake formation, EPSc and SMPc decided the structure of biocake and had no temporal changing science then. Microbial started to use part of EPSp, and extracted SMPp by product.