Abstract：In order to improve total nitrogen (TN) removal efficiency, influent flow rate distribution and volume of each treatment zone of step feeding A/O biofilm process were optimized simultaneously. Optimization of influent flow rate distribution was based on the principle that the concentration ratio of chemical oxygen demand (COD) to nitrate nitrogen of the influent of each anoxic zone was same and equaled an optimum ratio, and the volume of each treatment zone was designed based on the idea of equal volume loading. A three-step feeding A/O biofilm process was utilized to test the differences of effluent quality between the equal flow rate distribution mode and the optimization mode. The experimental results indicated when step feeding A/O process was operated under the two modes with the same operation parameters, the TN removal efficiency under the optimization mode arrived at 88.8%, which was superior to that of 80.3% of under the equal flow rate distribution mode; The COD removals and total Kjeldahl nitrogen removals of the process under the two modes were higher than 97% and 98% respectively. The optimization method presented in this study can improve the TN removal of step feeding A/O process significantly.
