The Study On N2O Emission Characteristics In Four Typical Urban Wastewater Treatment Processes

N2O is one of the three important greenhouse gases, the wastewater treatment plant is the main source of N2O emission, we made more study on N2O emission in library. Our study chose four typical treatment processes(A/O process、A2O process、oxidation ditch process and SBR process), made N2O sampling monitoring, and studied N2O emission characteristics in the four typical treatment processes.The paper developed two kinds of N2O gas sampling devices, which were used separately to collect N2O gas from every non-aeration processing unit (static box) and N2O gas from every aeration processing unit in the sewage treatment process (gas bag), moreover, we collected N2O dissolved in the water with static headspace analysis.Our study chose four typical treatment processes and made sampling monitoring from May2011to January2012. collected N2O gas and N2O dissolved in the water once a month. At the same time, we monitored and anlysised water quality index in every wastewater treatment plant.The experimental results indicated:In the four typical treatment processes, the effect on N2O emission made by DO concentration was the most obvious. The main source of N2O were aerated units, most N2O gas from the aeration units was blowed off, and N2O emmisions in the aeration units accounted for96percent in the whole process. N2O gas from non-aeration units was little, N2O concentration dissolved in the water was more or less the same. N2O emmisions flux (mg/m:/day): aeration phase in the SBR process> aeration phase in the A2O process> aeration phase in the A/O process> aeration phase in the Oxidation ditch process. N2O emmisions came from per ton wastewater (g/t):SBR process>A/O process>A2O process>Oxidation ditch process. In A/O、A2O and Oxidation ditch processes, N2O emissions had the opposite trend with the change of COD/N. The water temperature and pH made no difference with N2O gas emissions.