Sulfide-driven nitrous oxide recovery during the mixotrophic denitrification process

We propose a novel sulfide-driven process to recover N 2 O during the traditional denitrification process. The optimum initial sulfide concentration was 120 mg/L, and the N 2 O percentage in the gaseous products (N 2 O + N 2 ) was up to 82.9%. Moreover, sulfide involved in denitrification processes could substitute for organic carbon as an electron donor, e.g., 1 g sulfide was equivalent to 0.5-2 g COD when sulfide was oxidized to sulfur and sulfate. The accumulation of N 2 O was mainly due to the inhibiting effect of sulfide on nitrous oxide reductase (N 2 OR), which was induced by the supply insufficiency of electrons from cytochrome c (cyt c ) to N 2 OR. When the initial sulfide concentration was 120 mg/L, the N 2 OR activity was only 36.8% of its original level. According to the results of cyclic voltammetry, circular dichroism spectra and fluorescence spectra, significant changes in the conformations and protein structures of cyt c were caused by sulfide, and cyt c completely lost its electron transport capacity. This study provides a new concept for N 2 O recovery driven by sulfide in the denitrification process. In addition, the findings regarding the mechanism of the inhibition of N 2 OR activity have important implications both for reducing emissions of N 2 O and recovering N 2 O in the sulfide-driven denitrification process. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

This study proposes a novel sulfide-driven process to recover N2O during denitrification. Results show that sulfide inhibits the activity of nitrous oxide reductase (N2OR), leading to N2O accumulation. Additionally, sulfide can substitute for organic carbon as an electron donor. The study also reveals that sulfide induces significant changes in the conformation and protein structure of cytochrome c, causing a loss of electron transport capacity.