DO对短程反硝化过程中N_2O产量的影响

Effect of DO on N_2O emission during nitrite denitrification process

利用SBR反应器,考察不同溶解氧(DO)条件下NO2-反硝化过程中N2O产生及释放过程。研究结果表明:控制曝气量为0.3 L/min,进水NO2--N质量浓度为40 mg/L,体系DO质量浓度分别为0,0.1,0.3,0.5和0.7 mg/L时,反硝化过程N2O释放量分别为0.41,0.60,2.62,4.98,6.83 mg/L;随DO质量浓度的增加,反硝化速率明显降低;当DO质量浓度由0 mg/L增至0.7 mg/L时,每克混合液悬浮固体(MLSS)的NO2-反硝化速率由14.9 mg/(L.h)降至10.2 mg/(L.h),每克MLSS的N2O产生速率由0.2 mg/(L.h)增至1.9 mg/(L.h)。其原因为:高DO质量浓度对氧化亚氮还原酶具有较强的毒性,抑制了N2O的进一步还原过程;高NO2-的存在导致抑制了氧化亚氮还原酶的活性。降低A/O和A2/O等生物脱氮过程中缺氧反应器内部DO质量浓度,保证严格缺氧条件,是减少短程生物反硝化过程中N2O产量的关键因素。

The effect of DO （Dissolved oxygen） on the kinetics of nitrite denitrification, as well as the corresponding N2O accumulation and emission were investigated using 2.4 L sequencing batch reactor. The results show that NaNO2 is added at the initial of the test to the final NOz--N mass concentration of 40 mg/L. The aeration rate is controlled at 0.3 L/min and the ratio of Nz to O2 is adjusted so that the DO can be controlled at 0, 0.1, 0.3, 0.5 and 0.7 mg/L and the N：O emission is 0.41, 0.60, 2.62, 4.98, 6.83 rag/L, respectively. The denitrification rate decreases with the increase of DO mass concentration. The nitrite reduction rate per gram of mixed liquor suspended solid （MLSS） decreases from 14.9 to 10.2 mg/（L.h）, while the N2O emission rate per gram of MLSS increases from 0.2 to 1.9 mg/（L.h）. The reason may be that higher DO mass concentration inhibits the activity of N2O reductase thus results in higher N2O production as to higher N2O emission. Besides, higher nitrite presence inhibits the activity of nitrous oxide reduction enzymes which is responsible for N2O reduction. To reduce DO mass concentration in anoxic tanks during nitrogen removal process may be the efficient way to reduce N2O emission durin~ nitrite denitrification process.