Responses of nitrogen transformation processes and N2O emissions in biological nitrogen removal system to short-term ZnO nanoparticle stress

Although the adverse effects of ZnO nanoparticles (ZnO NPs) on biological nitrogen removal (BNR) processes have widely been reported, the impacts of ZnO NPs on the whole nitrogen transformation processes, especially the production of nitrous oxide (N2O), a typical greenhouse gas in a BNR system have...

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Bibliographic Details
Published in:The Science of the total environment 2020-02, Vol.705, p.135916-135916, Article 135916
Main Authors: Ye, Jinyu, Gao, Huan, Wu, Junkang, Chang, Yan, Chen, Zhoukai, Yu, Ran
Format: Article
Language:English
Subjects:
Biological nitrogen removal
N2O emission
Nanotoxicity regulation
Nitrogen transformation
ZnO nanoparticles
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Summary:Although the adverse effects of ZnO nanoparticles (ZnO NPs) on biological nitrogen removal (BNR) processes have widely been reported, the impacts of ZnO NPs on the whole nitrogen transformation processes, especially the production of nitrous oxide (N2O), a typical greenhouse gas in a BNR system have rarely been systematically studied yet. In this study, the performances of both the nitrification and denitrification processes were investigated and the N2O emission was simultaneously monitored in a sequencing batch reactor (SBR) when exposed to 1, 25 or 50 mg/L ZnO NPs for one cycle. The dose-dependent ZnO NP depression effects were generally observed on denitrification processes, total nitrogen (TN) removal efficiency and N2O emissions but not nitrification process. Meanwhile, the N2O emission was positively correlated with NO2−-N accumulation in the oxic stage. Further investigation showed that the expressions of nitrate (NO3−) reduction associated narG gene were down-regulated with the increase of NP stress, and the transcript ratios of NO2−/NO reduction gene to N2O reduction one (nirK/nosZ and norB/nosZ) decreased. The released Zn2+ from ZnO NPs took an important role in the inhibition of denitrification processes. ZnO NPs addition also induced the dose-dependent variations in the superoxide dismutase (SOD) and catalase (CAT) activities, which probably contributed to the suppression of the excess reactive oxygen species (ROS) generations to mitigate nanotoxicity. The excessive secretion of protein (PN) in tightly bound EPS (TB-EPS) when ZnO NPs were no
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2019.135916