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Electrons transfer determined greenhouse gas emissions in enhanced nitrogen-removal constructed wetlands with different carbon sources and carbon-to-nitrogen ratios

Chen, Danyue, Gu, Xushun, Zhu, Wenying, He, Shengbing, Huang, Jungchen, Zhou, Weili
Bioresource technology 2019 v.285 pp. 121313
bacteria, carbon, carbon nitrogen ratio, chemical oxygen demand, constructed wetlands, denitrification, electrons, genes, global warming potential, glucose, greenhouse gas emissions, greenhouse gases, methane production, microbial communities, nitrites, nitrogen, nitrous oxide, sodium acetate
A constructed wetland (CW) was established to explore the influence of carbon addition (glucose or sodium acetate) on nitrogen removal and greenhouse gas (GHG) emissions at chemical oxygen demand to nitrogen ratios (COD/Ns) of 0, 4, 7. Results showed that the type of carbon source and COD/N significantly influenced the CW performance, in which the electrons transfer determined the regulation of denitrification, methanogenesis and respiration. Higher N2O emissions were consistent with higher nitrite accumulation at low COD/N because of electrons competition. The residual carbon source after near-complete denitrification could be further utilized by methanogenesis. Sodium acetate was superior to glucose in promoting denitrification and reducing global warming potential (GWP). In addition, bacteria sequencing and functional genes confirmed the important role of the type of carbon source on controlling nitrogen removal, carbon consumption and GHG emissions in microbial communities.