Analysis and mitigation of N2O emissions in biological wastewater treatment – N2OTrack

Nitrogen protoxide (N2O) is a powerful greenhouse gas (GHG), with an impact 300 times higher than carbon dioxide, contributing significantly to global warming. Microbial processes (nitrification or denitrification) in soils or water contribute significantly to the production of N2O. To date, the contribution of wastewater management is still controversial as N2O emissions were poorly measured in wastewater treatment plants. Recent campaigns demonstrated however that the values assumed by the IPPC are much lower than reality. Moreover intensification of nitrogen removal in wastewater treatment and innovation for minimizing energy consumption can potentially increase the N2O emissions if nitrification and denitrification are insufficiently controlled with appropriate tools.

This project aims to quantify, model and reduce N2O emissions from wastewater treatment facilities. The ambition of the project is to evaluate solutions in intensive processes receiving domestic wastewater which are used for nutrient removal.

The project is divided in different tasks: (1) monitoring of full scale systems during long term campaigns, (2) tracking the main microbial pathways by innovative techniques (isotopes signature and NO:N2O ratio), (3) validation of a multiple pathway model for simulation and evaluation of mitigation strategies, (4) demonstration of innovative sensors and control tools for energy reduction and N2O mitigation.

N2OTRACK will provide representative and objective information on direct greenhouse gas emissions from depollution systems. The contribution of these systems to the national anthropogenic N2O emissions will be estimated. Special effort will be deployed on biofilters at full scale, systems poorly characterized so far.

The aim is also to provide an N2O modelling framework validated by lab-scale data with isotopic signature measurements and calibrated by full scale campaigns. Finally innovative control tools based on well-known and new sensors will be developed for both activated sludge processes and biofilters.

The project involves six partners: three academic laboratories (LISBP-INSA, IEES-UPMC, RBPE-ECOBIO), one applied research institute (IRSTEA), a large WWTP facility (SIAAP-Paris) and a private company SME (BIOTRADE).