Simulation study on effects of different A/O partitions of oxidation ditches on nitrogen removal
氧化沟不同A/O分区对脱氮效果影响的模拟实验研究

The three different oxidation ditches with 2, 4 and 7 A/O partitions were simulated via three different aeration modes. The effects of the numbers of partition on the way and efficiency of nitrogen removal were investigated. The results show that the average DO concentration in aerobic zone is small and the activity of nitrobacteria is low with more A/O partitioning under the same ratio of the aerobic and anoxic zone. The nitrobacteria activities are 4.80, 4.65 and 3.73 mg·g-1·h-1 when the numbers of A/O partition are 2, 4 and 7, respectively. As the numbers of A/O partition are less, the aerobic and anoxic sections are longer in an A/O partition. Consequently, more organics are used to denitrify, resulting in higher oxygen utilization efficiency and better nitrification and denitrification efficiencies. The average removal efficiency of TN is 60.14%, 47.93% and 33.7% under the three different operation conditions, respectively. The average concentrations of TN are 17.01,22.17 and 27.92 mg·L-1 in effluent respectively. The ways of nitrogen removal are primarily via anoxic denitrification or simultaneous nitrification and denitrification (SND) in oxidation ditch. TN is removed mainly by SND under larger A/O partitions. On the contrary, anoxic denitrification is predominant in smaller A/O partitions. TN removal efficiency in SND is lower than in anoxic denitrification because of insufficient organics.