Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium.
Water Res. 2015 Jan 1;68:793-803. doi: 10.1016/j.watres.2014.10.056.
N₂O emission from wastewater treatment plants is high of concern due to the strong environmental impact of this greenhouse gas. Good understanding of the factors affecting the emission and formation of this gas is crucial to minimize its impact. This study addressed the investigation of the N₂O emission dynamics in a full-scale one-stage granular sludge reactor performing partial nitritation-anammox (PNA) operated at a N-loading of 1.75 kg NH₄⁺-N m⁻³ d⁻¹. A monitoring campaign was conducted, gathering on-line data of the N₂O concentration in the off-gas of the reactor as well as of the ammonium and nitrite concentrations in the liquid phase. The N₂O formation rate and the liquid N₂O concentration profile were calculated from the gas phase measurements. The mean (gaseous) N₂O-N emission obtained was 2.0% of the total incoming nitrogen during normal reactor operation. During normal operation of the reactor under variable aeration rate, intense aeration resulted in higher N₂O emission and formation than during low aeration periods (mean N₂O formation rate of 0.050 kg N m⁻³ d⁻¹ for high aeration and 0.029 kg N m⁻³ d⁻¹ for low aeration). Accumulation of N₂O in the liquid phase was detected during low aeration periods and was accompanied by a relatively lower ammonium conversion rate, while N₂O stripping was observed once the aeration was increased. During a dedicated experiment, gas recirculation without fresh air addition into the reactor led to the consumption of N₂O, while accumulation of N₂O was not detected. The transition from a prolonged period without fresh air addition and with little recirculation to enhanced aeration with fresh air addition resulted in the highest N₂O formation (0.064 kg N m⁻³ d⁻¹). The results indicate that adequate aeration control may be used to minimize N₂O emissions from PNA reactors.
污水处理厂的 N₂O 排放是一个令人高度关注的问题，因为这种温室气体对环境的影响很大。充分了解影响这种气体排放和形成的因素对于最大限度地减少其影响至关重要。本研究针对在一个全规模的单级颗粒污泥反应器中进行部分硝化-厌氧氨氧化（PNA）的过程中 N₂O 排放动力学进行了研究，该反应器的氮负荷为 1.75 kg NH₄⁺-N m⁻³ d⁻¹。进行了一项监测活动，在线收集了反应器废气中 N₂O 浓度以及液相中铵和亚硝酸盐浓度的数据。通过气相测量计算了 N₂O 生成速率和液相 N₂O 浓度分布。在正常反应器运行期间，获得的平均（气态）N₂O-N 排放量为总输入氮的 2.0%。在反应器变曝气率的正常运行期间，强烈曝气比低曝气期产生更高的 N₂O 排放和形成（高曝气时的平均 N₂O 生成速率为 0.050 kg N m⁻³ d⁻¹，低曝气时为 0.029 kg N m⁻³ d⁻¹）。在低曝气期检测到液相中 N₂O 的积累，同时伴随着相对较低的铵转化率，而一旦增加曝气，则观察到 N₂O 汽提。在专门的实验中，在没有新鲜空气进入反应器的情况下进行气体再循环导致 N₂O 的消耗，而没有检测到 N₂O 的积累。从长时间没有新鲜空气进入和很少再循环过渡到增加新鲜空气的增强曝气，导致 N₂O 的形成量最高（0.064 kg N m⁻³ d⁻¹）。结果表明，适当的曝气控制可用于最大限度地减少 PNA 反应器的 N₂O 排放。
