N2O emission from a nitritation double-sludge system treating wastewater with a high concentration of ammonium

Abstract

<p>A high efficient nitrite based double-sludge system combining sequential denitrification and nitritation reactors has been developed to remove nitrogen from wastewaters containing high concentrations of ammonium. System performance was examined and also nitrous oxide (N<sub>2</sub>O) emission was measured under different aeration rates with or without the addition of nitrite nitrogen (NO<sub>2</sub>-N). The nitritation efficiency (the ratio of NO<sub>2</sub>-N to the oxidized nitrogen, NO<sub>X</sub>-N) reached to 99.8% at the ammonium loading rate of 1.47 g l<sup>-1</sup> d<sup>-1</sup>. With increasing the aeration rate, ammonium oxidizing rate increased, indicating that the activity of ammonia oxidizing bacteria was enhanced. However, N<sub>2</sub>O emission decreased with increasing the aeration rate. N<sub>2</sub>O emission was high with the addition of NO<sub>2</sub>-N. The aeration rate had a high effect on N<sub>2</sub>O emission at high initial NO<sub>2</sub>-N concentrations, with the N<sub>2</sub>O emission factor ranged from 0.59% to 1.64%. While the effect of aeration rate on N<sub>2</sub>O emission was not significantly without the addition of NO<sub>2</sub>-N, with the emission factor of only around 0.20% to 0.27%.</p>