Research On Characteristic Of Nitrogen Removal By A/O MBR

In this paper, A/O membrane bioreactor was used to treat municipal waste water to investigate the treatment effect and operation conditions. The effect of operation parameters on nitrogen removal was analyzed. So this experiment may offer theoretical and practical reference for the membrane bioreactor's nitrogen removal application.The experimental results show that A/O membrane bioreactor system can obtain a good removal of turbidity. The turbidity of effluent is around 1NTU for most of the time. The average removal efficiency of CODcr is 85.33%, the CODcr of effluent are under 38.9mg/L, and the quality of A/O membrane bioreactor effluent can keep stable even under strong impact. It has an ideal removal of NH3-N, and the NH3-N of effluent can be basically under 1mg/L. Although the film itself contributes little to the removal of NH3-N, a lot of nitrobacteria can be retained by the film to strength the removal of NH3-N. However, the removal of TN is unstable.The treatment effect of NH3-N and TN is investigated when the air-water ratio is 30:1, 40:1, and 50:1 respectively. The results show that, when the air-water ratio rises from 30:1 to 40:1, it can obviously be benefit to the removal of NH3-N, but the removal efficiency of NH3-N improves little while the air-water ratio rises from 40:1 to 50:1. The average removal efficiency of TN declines with the air-water ratio increasing. Therefore, it needs a comprehensive consideration of TN and NH3-N to select a appropriate air-water ratio for actual operation. When the air-water ratio is 40:1, the analysis of reflux ratio effect on the NH3-N and TN removal shows that: When the reflux ratio is 230%, 200% and 100%, the average removal efficiency of NH3-N is 99.6%, 99.2%and 98.3% respectively, reflux ratio has little effect on removal of NH3-N, but the system has the most stable removal efficiency of NH3-N when the reflux ratio is 230%. However, with the reflux ratio decreasing, the average removal efficiency of TN first increases and then decreases, with all things considered, the reflux ratio of 200% is more suitable for actual operation. In the early period of the experiment, the removal of NH3-N and TN increases with the MLSS(Mixed Liquor Suspended Solids) increasing, when the MLSS reaches 4500mg/L, the stability of NH3-N removal is enhanced, and the removal efficiency no longer changes along with that of MLSS. TN removal efficiency get a relatively good result when the MLSS reaches 6000mg/L, and higher MLSS can not guarantee higher TN removal efficiency, even may cause aging of sludge which can decline TN removal efficiency and stability. In this experiment, we determined the nitrification activity of the activated sludge. Its nitrification activity is less by an order of magnitude than cultured nitrobacteria. After adding additional organic carbon resource in the anoxic mixed liquid, the denitrification activity increases, and denitrification can conduct more completely. So we can improve the system's TN removal through adding carbon resource in anoxic tank.