Modelling N2O production and emissions

Mathematical modelling of N2O emissions is of great importance for the understanding and reduction of the environmental impact of wastewater treatment systems. This chapter reviews the current status of the modelling of N2O emissions from wastewater treatment. The existing mathematical models describing all known microbial pathways for N2O production are reviewed and discussed. These include N2O production and consumption by heterotrophic denitrifiers, N2O production by ammoniaoxidizing bacteria (AOB) through the hydroxylamine oxidation pathway and the AOB denitrification pathway and the integration of these pathways in single-pathway N2O models. The two-pathway models are compared to single-pathway models. The calibration and validation of these models using lab-scale and full-scale experimental data is also reviewed. The mathematical modelling of N2O production, while still being enhanced by new knowledge development, has reached a maturity that facilitates the estimation of site-specific N2O emissions and the development of mitigation strategies for wastewater treatment plants taking into account the specific design and operational conditions of the plant.