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

Abstract

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 (N2O) emission was measured under different aeration rates with or without the addition of nitrite nitrogen (NO2-N). The nitritation efficiency (the ratio of NO2-N to the oxidized nitrogen, NOX-N) reached to 99.8% at the ammonium loading rate of 1.47 g l -1 d -1. With increasing the aeration rate, ammonium oxidizing rate increased, indicating that the activity of ammonia oxidizing bacteria was enhanced. However, N2O emission decreased with increasing the aeration rate. N2O emission was high with the addition of NO2-N. The aeration rate had a high effect on N2O emission at high initial NO2-N concentrations, with the N2O emission factor ranged from 0.59% to 1.64%. While the effect of aeration rate on N2O emission was not significantly without the addition of NO2-N, with the emission factor of only around 0.20% to 0.27%.