Effects of carbon source on N2O production in the process of simultaneous nitrification and denitrifica-tion via nitrite by aerobic granular sludge

Abstract

A sequencing batch reactor (SBR) was used to study the effect of carbon source (C₆H₁₂O₆ and CH₃COONa) and C/N ratio (C/N=4:1 and C/N=7:1) on the production of nitrous oxide (N₂O) in the process of simultaneous nitrifica-tion and denitrification via nitrite (short-cut SND) by aerobic granular sludge and the removal efficiency of nitrogen under low dissolved oxygen (DO). The results showed that short-cut SND occurred in this system, and the removal ef-ficiency of total nitrogen (TN) at C₆H₁₂O₆ and CH₃COONa were 28.93 % and 41.19 %, respectively. However, the production of N₂O significantly increased when CH₃COONa was used as a carbon source. In addition, the rate of N₂O release when CH₃COONa was a carbon source was 8.34 times the rate when C₆H₁₂O₆ was the carbon source. With the increase of C/N, removal rate of TN and the efficiency of the short-cut SND were increased. The removal efficiency of TN at C/N=7:1 was 90.33%, which was 2.19 times at C/N=4:1. The percentage of short-cut SND at C/N=4:1 and C/N=7:1 were 87.47% and 95.97%, respectively. The release rate of N₂O from the original 1.14 mg/(g • min) decreased to 0.10 mg/(g • min) after increased the C/N from 4:1 to 7:1.