Optimization for Nitrogen Removal in Anoxic/Oxic⁃Membrane Bioreactor by Response Surface Methodology

The optimal operating condition for the total nitrogen(TN)removal in an anoxic/oxic⁃membrane reactor(A/O⁃MBR)was studied by employing response surface methodology(RSM),which is a statistical test method for optimizing stochastic processes.The individual and interactive influences of three operating parameters including dissolved oxygen in aerobic tank(DO),internal mixed liquor recycle rate(IR),and mixed liquor suspended solids(MLSS)on the TN removal efficiency were evaluated.TN removal efficiency increased first and then reduced with the increase of DO,IR,and MLSS.Results from RSM indicated that the three factors had significant interactive influences on the TN removal efficiency.Meanwhile,the interaction between DO and MLSS had more significant effects on the TN removal efficiency than those of the other two.The maximum TN removal efficiency was forecasted at 83.34%according to the model when MLSS was 7926.6 mg/L,IR was 371.8%,and DO was 3.5 mg/L.Under this optimum condition,the experimental TN removal efficiency was 83.13%,which further confirmed that the optimum strategy was reliable.