CFD modelling of N2O emission from surface aerated activated sludge reactors – Systematic mesh refinement and sensitivity analysis

Y. Qiu, C. T. Griffin, S. Ekström, B. Valverde Pérez, B. F. Smets, J. Climent, C. Domingo-Felez, R. Martínez Cuenca, Benedek G. Plósz

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The effective numerical prediction of nitrous oxide (N2O) emission – a potent greenhouse gas – from biological wastewater treatment plants (WWTPs) is crucial for developing effective climate change mitigation measures for urban water systems. Based on previous research (Qiu et al., 2019), the novel method for estimating the alpha factor and the stripping gas mass transfer coefficient for N2O (kLaN2O) was developed using experimental and CFD simulation data. By combining hydrodynamics, gas mass transfer and the NDHA biokinetic model, a threedimensional, single-phase, CFD simulation model of a surface-aerated activated sludge oxidation ditch has been developed. The main aims of this study include (i) mesh refinement of the current three-dimensional, singlephase, CFD model by employing the grid convergence index (GCI); (ii) assessing the impact of mesh refinement on predicting N2O emission from activated sludge reactor; and (iii) quantifying
the relative sensitivity of model outputs associated with the prediction of N2O emission to selected design and flow boundary conditions, thereby identifying areas for improving reactor design and operation.
Original languageEnglish
Title of host publicationWRRmod2021 Conference Proceedings
Publication date2021
Article numberP124
Publication statusPublished - 2021
Event7th IWA Water Resource Recovery Modelling Seminar - Virtual seminar
Duration: 21 Aug 202125 Aug 2021


Conference7th IWA Water Resource Recovery Modelling Seminar
LocationVirtual seminar


  • Activated sludge wastewater treatment
  • Computational fluid dynamics
  • Grid convergence index
  • Nitrous oxide emission


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