Contribution of dissolved N2O in total N2O emission from sewage treatment plant

• Published in: Chemosphere (Oxford) 2018-12, Vol.212, p.821-827
• Main Authors: Masuda, Shuhei, Otomo, Shohei, Maruo, Chikako, Nishimura, Osamu
• Format: Article
• Language: English
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2018.08.089

The characteristics of nitrous oxide, N2O, from a sewage treatment plant, which conducts nitrogen removal, and the river that receives its effluent water, were investigated by intensive daily surveys in summer and winter. N2O production in the sewage treatment plant was promoted in winter when nitrite accumulated in the reaction tank. The dissolved N2O concentration in the effluent water was also high in winter, which caused the dissolved N2O concentration to increase in the river downstream. In contrast, the N2O production inside the plant and the dissolved N2O emission through the effluent water, the dissolved N2O discharge, was controlled in summer when the nitrogen removal was more complete and there was no-nitrite accumulation. The dissolved N2O in the effluent water was rapidly lost after leaving the plant by as much as 26% in summer and 59% in winter. Additionally, the amount of the dissolved N2O discharge in winter was almost equal to that of the indirect N2O emission. When the nitrogen removal proceeded successfully, the amount of dissolved N2O discharge was small. In contrast, when the nitrogen removal was insufficient, the dissolved N2O discharge became an important N2O source. [Display omitted] •N2O profiles in STP and the river receiving its effluent were investigated.•N2O production was promoted with nitrite accumulation in the reaction tank in winter.•DN2O in the effluent water was immediately gasified by as much as 26%–59%.•The amount of the DN2O discharge was almost equal to that of indirect emission in winter.•DN2O discharge becomes an important source when the nitrogen removal is insufficient.