Copper-ion-mediated removal of nitrous oxide by a salt-tolerant aerobic denitrifier Halomonas sp. 3H

Abstract

Nitrous oxide (N2O) is a greenhouse gas mainly produced during the denitrification process in the treatment of wastewater, especially saline wastewater. N2O production increases with salinity. In this study, Halomonas sp. 3H was isolated from a eutrophic saline lake sediment. It exhibited high saline–alkaline tolerance. The strain possessed complete-denitrification-related gene clusters (narIJHGXLK, nirSBD, norEDQBC, and nosLYFDZR). Under shaking at 150 rpm, it could completely remove ammonium nitrogen (100 mg/L) via assimilation and nitrate or nitrite nitrogen via denitrification in wastewater with high salinity (5% NaCl). During denitrification, approximately 40 mg/L N2O was produced. However, after the addition of Cu2+, only 1.3 mg/L N2O was produced, which was subsequently completely removed. Moreover, added N2O (13 mg/L) was completely removed by the strain 3H with the further addition of Cu2+(100–500 μg/L). In summary, Halomonas sp. 3H removed excess nitrogen and N2O from wastewater with high salinity in the presence of Cu2+ via aerobic denitrification. Therefore, this strain could contribute to mitigating complex and significant climate changes.