Managing nitrous oxide (N2O) emissions is a critical decarbonization challenge for the water industry. This presentation details an R&D collaboration between Singapore’s National Water Agency (PUB) and AM-Team to develop a proactive framework for N2O quantification and mitigation. The approach utilizes a two-tiered modelling strategy, integrating high-resolution 3D Computational Fluid Dynamics (CFD)-biokinetic models with computationally efficient dynamic spatial process models. Validated against onsite liquid and gas-phase monitoring data at a full-scale Water Reclamation Plant (WRP), the models identified primary emission hotspots and root causes—specifically heterotrophic denitrification triggered by transient COD limitations. Key findings demonstrate that the framework can accurately predict N2O dynamics and test mitigation strategies, such as optimizing COD availability, which showed a potential N2O reduction of up to 80%. The project is currently expanding to the Integrated Validation Plant (IVP) to apply this methodology to a Membrane Aerated Biofilm Reactor (MABR) and conventional AS technologies. This work establishes a robust roadmap for “minimal N2O by design,” balancing effluent quality and operational efficiency with ambitious decarbonization goals.