| Aiming at the inceasing serious eutrophication of received water. Step-feed A/O process was developed rapidly at home and abroad in recent years. The process shows the advantadge of high nitrogen removal efficiency, reduced reactor volnmn, flebiblity for operation and management. The research group studied on the current wastewater characteristics in Xi'an Beishiqiao sewage clarification Center. Applied with a step-feed A/O process which disgned and constructed by ourselves, to develop the criteria for optimum selection of design and operation parameters.The design influent flow was 160L/h and splitted to four points in the experiment, we have studied two cases for the process performance. In the first case, the influent was splitted equally tofoue stages and the volumetric ratio of anoxic to oxic is 1 to 3.The removal efficiency of TCOD.SCOD.TN could reach 92%. 88% and 65% respectively, and the effluent NH4-N was kept below 1mg/L.In the second case, the influent split ratio was 25%.35%.30% and 10%,the volumetric ratio of anoxic to oxic in the first stage was set 1 to 2,and 1 to 1 in the following stages. The removal efficiency of TCOD. SCOD and TN was observed to be 89%. 85% and 73% respectively.The experiment results demonstrated that complete nitrification were carried out in the first case, while insufficient denitrification was observed, By adjusting the influent splitting ratio to each stage and increasing the volumn of anoxic tanks, the denitrification was enhanced and the TN removal efficiency accordingly. However, the second case is not the optimum operating conditions which needs further studies.
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