Effect of Aeration Intensity on Nitrous Oxide Production

概要

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Nitrous oxide (N2O) is known as one of the strong greenhouse gases and is emitted from aeration tanks of biological wastewater treatment plant. Strategy to control N2O emission from aeration tanks, however, has not been developed yet. We operated two identical pilot-scale anaerobic-anoxic-oxic (A2O) reactors to examine the effect of aeration intensity, especially to the first aerobic tank on N2O emission. The results indicate that the intensive aeration to the first aerobic tank increased N2O emission along with rapid ammonia oxidation and nitrite accumulation. On the contrary, moderate aeration provided gradual oxidation of ammonia, less nitrite accumulation and less N2O production. Batch tests with varied aeration intensities also demonstrated that intensive aeration enhances ammonium oxidation, resulting in the increased nitrite accumulation and the elevated N2O production, except in the case with high DO concentration (more than 2 mg/L). The conversion ratio of ammonia to N2O has good correlation to nitrite and nitrite/DO ratio. The effect of DO is complicated and still unclear. Mechanism of the elevated conversion to N2O is the effect of nitrite accumulation and might be the metabolic change of AOB.
Japan Society on Water Environmentの論文