Computational fluid dynamics modelling of sewage sludge mixing in an anaerobic digester

In this paper, the development of a computational fluid dynamics (CFD) model to simulate the mechanical mixing of sewage sludge at laboratory scale is reported. The paper recommends a strategy for modelling mechanically mixed sewage sludge at laboratory scale. Generated flow patterns are analysed and conclusions drawn as to the effectiveness of mixing in the laboratory scale digester. Data relating biogas yield to different mixing regimes are reported and combined with CFD model results. From this, novel conclusions regarding velocity gradients and biogas yield are drawn.