限氧自养亚硝化过程中N_2O的释放特征

CHARACTERISTICS OF NITROUS OXIDE EMISSION DURING AUTOTROPHIC PARTIAL NITRIFICATION UNDER OXYGEN-LIMITED CONDITION

实验采用SBR工艺,在限氧曝气条件下,研究自养亚硝化(进水中不含有机碳)过程中N_2O的释放特征。结果表明,在限氧自养亚硝化过程中,不同进水氨氮浓度条件下的溶解氧浓度均为(0.08±0.02)mg/L,氨氧化速率基本不受氨氮浓度变化的影响,即自养亚硝化反应呈零级反应。进水氨氮浓度为60,120,240 mg/L时的N_2O释放总量分别为3.24,8.75,24.59 mg/L,相应的N_2O释放因子依次为0.12、0.17和0.22。限氧曝气条件下,氨氧化菌(AOB)反硝化产生N_2O占主导作用。进水氨氮浓度越高时,亚硝化过程需时越长,后期NO-2-N累积量越大,导致AOB反硝化产生N_2O的速率越大,N_2O释放总量和释放因子(N_2O释放量/NH+4-N去除量)也越大。

A lab-scale SBR was developed to investigate the characteristics of nitrous oxide（ N_2O） emission in the process of autotrophic partial nitrification under oxygen-limited condition. Results showed that ammonia oxidizing rates and dissolved oxygen（ 0. 08 ± 0. 02） mg / L concentrations maintained constant with the variation of influent ammonia concentrations. In other words,the ammonia oxidation was a zero order reaction in autotrophic partial nitrification. When the influent ammonia concentrations were 60,120 and 240 mg / L,the total N_2 O emissions were 3. 24,8. 75,24. 59 mg / L,and the corresponding N_2 O emission factors（ the ratio between N_2 O nitrogen emitted and the ammonium nitrogen converted） were 0. 12,0. 17 and0. 22,respectively. Under low-oxygen condition,the ammonia oxidizing bacteria（ AOB） denitrification was attributed as the dominant source of N_2 O production on autotrophic nitritation. The N_2 O emission increased significantly with the increase of ammonia concentration from 60 to 240 mg / L. A higher ammonia nitrogen input resulted in a larger accumulation of nitrite during nitritation. And a higher nitrite concentration in liquid led to more N_2 O production by AOB denitrification.