关键词: 膜生物反应器, 活性污泥, 氧的传质, 氧传递速率, a值

Abstract: In comparison with the conventional activated sludge process, membrane bioreactor (MBR) offers the advantages of a smaller footprint due to higher biomass concentrations and a complete removal of solids from the effluent. As aeration system for fouling control and oxygen supply counts for more than 90% of total energy cost in MBR, it is important for the design of the aeration system. Generally operational cost and mixed liquid suspended solids (MLSS) concentration were inversely proportional to each other, which means that membrane flux and a value are minimized when MLSS concentration is maximized and vice versa. Therefore, MLSS concentration was considered to be a key parameter for the operation of MBR. In order to achieve the optimum MLSS concentration, the relationship between these parameters (including membrane flux, a value and pollutant removal rate) and MLSS (3.9~18.4 g/L) were investigated in the study. It clearly showed that viscosity of sludge increased with higher MLSS. The viscosity of sludge increased from 5.4 mPa×s at MLSS of 4.8 g/L to 680 mPa×s at MLSS of 18.4 g/L. The relationship between viscosity of sludge and MLSS can be indicated with the equation h=e0.1635c+0.055. The a value, which defines the relation of oxygen transfer in pure water to oxygen transfer in activated sludge, decreased from 0.89 at MLSS of 4.8 g/L to 0.10 at MLSS of 18.4 g/L. However, the MLSS concentration had no impact on pollutant removal rate of COD, NH4+-N and TN when MLSS exceeded 4.8 g/L. Therefore, optimum MLSS concentration was turned out to be 4 g/L to 6 g/L in the case of typical municipal wastewater.

Key words: membrane bioreactor, activated sludge, oxygen transfer, specific aeration efficiency, a value