Hydrodynamic and biochemical Computational Fluid Dynamic modelling of full-scale anaerobic digesters for wastewater treatment

Abstract

Anaerobic digestion is one of the most widely used biological treatments for the stabilisation of sewage sludge, but the effectiveness of the process depends on good mixing. The Computational Fluid Dynamics (CFD) technique allows analysing the mixing and hydrodynamics, so it has been widely used to study anaerobic digestion. In this thesis, hydrodynamics in full-scale digesters have been studied by means of CFD models, evaluating their mixing systems by means of different scenarios according to mixing and design parameters and dead volumes. In a second part, a new CFD solver was developed to couple a biological model with hydrodynamics and applied to a laboratory and a full-scale digester. The last part was devoted to evaluate the hydrodynamic behaviour of biogas bubbles in anaerobic sludge, so that local mixing by biogas bubbles in anaerobic digesters was evaluated. Future work needs to focus on experimental measurements and new two-phase CFD models.