Monitoring, modelling and reducing nitrous oxide emissions from WWTPs

Towards mitigation strategies for WWTPs through intensive monitoring and modelling of N2O emissions

Industry and society are striving to reduce the carbon footprint in response to tackling climate change. But carbon dioxide is not the only harmful greenhouse gas – nitrous oxide (N2O) has a global warming potential  273 times greater than CO2. Wastewater treatment plants (WWTPs) are a significant source of N2O emissions. As a result, well-conceived long-term research is needed to better understand N2O production in WWTPs and find technologies and strategies to reduce it.


N2O emissions from WWTPs exhibit diurnal and seasonal variations. To better understand the processes behind its production, it is necessary to quantify the N2O emissions. Few WWTPs in the world currently monitor N2O emissions in real time, given that quantifying N2O emissions from open tanks is challenging. Advanced monitoring and measurement technologies exist to detect N2O in the gas phase, but in order to provide such analysers with representative and clean samples, a fit-for-purpose floating hood is needed to collect the off-gases in open tanks. The necessary datasets obtained can thus be used to calibrate biokinetic models that provide insight into the N2O production pathways and processes. Furthermore, new technologies, such as artificial intelligence (AI), to accurately forecast N2O emissions can be developed to enable potential solutions for controlling wastewater treatment processes in real time to reduce the harmful emissions.


In this project, we will intensively monitor selected WWTPs using advanced gas analysers. We will collect high-resolution data over a long duration to understand seasonal and diurnal variations. To effectively capture the emitted N2O gas from the open tanks of the wastewater treatment plant, we designed a fit-for-purpose floating hood which will be installed on the water surface, and connected to a gas analyser. We will combine the collected data with other measurements on the treatment processes provided by the waterboards, including the liquid phase N2O measurements. The datasets will be used to develop digital twins for the prediction of N2O emissions. These digital twins can be further used to develop N2O emissions control and reduction strategies.


At several Dutch wastewater treatment plants with different biological treatment process configurations, we will conduct robust monitoring campaigns of N2O emissions. The N2O gas sampling are done with a state-of-the-art fit-for-purpose floating hood, which is equipped with the necessary sensors (such as temperature and pressure) to record the sampling conditions and includes preventive maintenance mechanisms to ensure the collection of high-quality and representative gas samples. These samples are then analysed with industry-standard analytical equipment to measure the concentration of the emitted N2O. In doing so, we use equipment from KWR and new equipment from Douna Machinery B.V and Emerson Process Management B.V.

The data collected will allow us to determine the emission factor for N2O at different WWTPs. With the development of models and digital technologies, valuable insights into the processes of N2O production and emissions will be gained, leading to the development of effective N2O mitigation strategies. This project also provides important and complementary knowledge to the versnellingsprogramma in the Netherlands aiming at monitoring N2O emissions from WWTPs nationwide.