Effects of Exogenous Organic Carbon Substrates on Nitrous Oxide Emissions during the Denitrification Process of Sequence Batch Reactors

Nitrous oxide (N2O) is an important greenhouse gas and has significant impacts on the environment. N2O from denitrification process of wastewater treatment is one of the important anthropogenic sources. It is released as an intermediate of the denitrification reaction that consumes organic substrates as electron donors. The purpose of this study was to determine the optimal carbon substrates to suppress N2O emissions. Exogenous organic carbons including glucose, sucrose, and sodium acetate were used to assess their effects on N2O emissions and denitrification potential during the denitrification process of sequence batch reactors (SBRs). The results showed that the types of organic carbon substrates and the COD/N-NO3− ratio had great influences on the production of N2O and denitrification potential. N2O emissions and the denitrification efficiency increased with the increasing COD/N-NO3− ratio. The optimal COD/N-NO3− ratios of the denitrification potential was 7.59, 8.11, and 4.6 for glucose, sucrose, and sodium acetate respectively. At the optimal COD/N-NO3- ratios, nitrate removal rates were 98.8%, 99%, and 99%, total nitrogen removal rates were 90%, 77%, and 93.06 %, COD removal rates were 88.38%, 90.32%, and 97.29%, and their maximum N2O concentrations were about 95, 78.5, and 7μL L−1 for glucose, sucrose, and sodium acetate, respectively. Moreover, sodium acetate was the optimal organic carbon substrate not only to suppress N2O emissions but also to promote the denitrification potential.