An innovative model-based protocol for minimisation of greenhouse gas (GHG) emissions in WRRFs

Water Resource Recovery Facilities (WRRFs) are big contributors to greenhouse gas (GHG) emissions and energy consumption. Aeration is the main source of energy consumption in these facilities and nitrous oxide (N2O) is the main form of direct emission which is produced during nitrification and denitrification processes through multiple potential pathways. Mathematical modelling is a widely used tool for optimisation of WRRFs and modelling protocols have been developed, which are widely used in the community. However, carbon footprint reduction has not been the main focus of these protocols. In this study, an innovative model -based protocol for minimising GHG emissions of WRRFs was developed using advanced mathematical modelling paradigms. The protocol was constructed based on three different cases for each of which a flow sheet model, a computational fluid dynamics (CFD) model and a knowledge -based risk assessment model were studied together with high frequency data collected by LESSDRONE (an automated wireless tool for measuring direct off -gas emissions). The risk assessment model helps identify high risk conditions while the CFD model provides valuable insights on the impact of hydrodynamics under non -ideal mixing conditions. The flow sheet model is used to test the proposed mitigation strategies and to provide in-silico data for the risk assessment model. The developed model- based protocol provides a robust guideline for water utilities to optimise their operations for minimising carbon footprint of WRRFs without compromising their removal efficiencies.