Effect of starvation time on NO and N2O production during heterotrophic denitrification with nitrite and glucose shock loading

Nitric oxide (NO) and nitrous oxide (N2O) production during biological nitrogen removal has been widely studied, however, the mechanism of starvation time on NO and N2O accumulation has not yet been well characterized. Nitrite denitrification, as a significant source of NO and N2O production, has received increasing attention. Therefore, the goal of this study was to investigate the effect of starvation time on NO and N2O accumulation during nitrite denitrification. Results showed that starvation time have a significantly effect on NO accumulation. High NO accumulation may be mainly related to the imbalance of electron distribution caused by feast after famine. N2O accumulation under all starvation tests included two stages, namely the exogenous denitrification and the endogenous denitrification. The N2O accumulation is mainly attributed to electron competition, free nitrous acid (FNA) inhibition, and starvation time. In addition, results suggest that moderate starvation time promotes the NO and N2O accumulation, especially, the starvation time affects NO accumulation more significantly than that of N2O. Interestingly, high dissolved oxygen (DO) was detected during NO detoxification, which is partly related to NO dismutation. The microbial community analysis revealed that the predominant bacterial genera were Phycisphaera, Thauera, Comamonas, Bdellovibrio, and Castellaniella, which belong to denitrifiers.