The effect of S/N ratio on NO and N2O accumulation during sulfide autotrophic denitrification

Abstract

Abstract Nitro oxide (NO) and Nitrous oxide (N2O) are inevitable intermediates of sulfide autotrophic denitrification (SAD) process, and have huge environmental hazard. This study investigated the produce mechanism and accumulation characteristic of NO and N2O in SAD process under different S/N ratios. The results showed that the lower S/N ratio, the higher NO accumulation. Which was due to the strong reducing effect of S2- and the electronic competition between nitrogen reductase. And under S/N ratio = 2, N2O level reached its peak, which was caused by electronic competition. When the S/N ratio = 1, although the electronic competition was more intense, the total amount of electrons was less, thus the N2O produced is lower than that produced when S/N=2. Microbial community analysis showed that Thiobacillus sp. (62.44%) was the predominant genus, and conducted the suldide-oxiding autotrophic denitrification process.