Pilot Study And Analysis On Step-feed A/O Process

In recent years, the step-feed A/O process has received great attention for its unique characteristics in the field of water pollution control. The study is stressing on the point that the impact of the design operating parameters such as: influent distribution, A/O volume ratio and return activated sludge (RAS) ratio to the nitrogen removal efficiency during the process of municipal wastewater treatment, and try to develop the criteria for the optimum design and operation parameters selection.The pilot-scale plant is located in Xi'an Beishiqiao sewage clarification center and the raw water is used in the study. The design influent flow is 160L/h and splitting to four points in the ratio of 4:3:2:1, the A/O volume ratio is set on 1:3 for each pass. The average TCOD and SCOD removal efficiency can reach 93.23%, 85.69%, respectively, which suggest that the process is efficient in organic removal. However, the TN removal efficiency is between 42.50% and 78.36% which the average efficiency only reaches 58.54% for the deterioration of the sludge settleability in the later period of the experiment while the raw water quality is fluctuating greatly. The phenomenon shows that the denitrification rate is limited because of organic deficiency in later passes. While, from the experiment results of other papers better treatment capacity was showed so the feasibility and the optimum operating parameters of the step-feed A/O process still need more study.