Impact of C/N Ratio on Nitrogen Removal Performance and N2O Release of Granular Sludge CANON Reactor

Abstract

To Explore a suitable C/N ratio for efficient nitrogen removal and simultaneously achieving N2O release reduction, ammonia-rich wastewater with sodium acetate as an organic carbon source in a granular sludge completely autotrophic nitrogen removal over nitrite (CANON) reactor under different C/N water conditions were studied to determine the reactor's nitrogen removal performance and N2O release. The results showed that the total nitrogen (TN) removal rate and the removal load tended to increase gradually with the increase of C/N, ranging from 0 to 2.0. When C/N=0, the TN removal rate was 56.50 mg·L-1 in 7 h; the highest TN removal efficiency was 49%. When C/N=2.0, the highest TN removal rate was 71.42 mg·L-1 in 7 h; the highest TN removal efficiency was 59.52%, and the contribution of CANON to nitrogen removal gradually decreased, whereas the denitrification contribution gradually increased. When △NO3--N/△TN=0.086, the contribution of CANON nitrogen removal was only 51.48% and that of denitrification was 48.52%. The N2O release volume and release ratio decreased with increasing C/N. When C/N=0, the N2O release volume and rate were the highest, namely 3.60 mg and 2.13%, respectively. The lowest N2O release volume and rate were 1.61 mg and 0.75%, respectively, when C/N=2.0.