Lagrangian solver for coupling hydrodynamics with biokinetic conversion modelling in anaerobic digesters.

Conventional anaerobic digestion models used in wastewater treatment plants suffer from inaccuracies due to the limited consideration given to hydrodynamics within the digester tank. A solution to this is to combine computational fluid dynamics simulations with anaerobic models. This paper introduces a novel methodology in the form of a software toolbox that implements the standard anaerobic digestion model no.1 in C++ and can interface with particle-based Lagrangian simulations. This method provides significantly more insights into the biochemical conversion process by accounting for the impact of the hydrodynamics on the biochemical reactions. The paper presents the background of the method along with a conceptual and numerical verification. It also presents a case study of a 3D lab scale digester comparing the results from the solver with the standard anaerobic digestion model. This integrated approach can be used by operators and designers for optimisations and also for predictive modelling.

Effect of turbulent diffusion in modeling anaerobic digestion.

In this study, the impact of turbulent diffusion on mixing of biochemical reaction models is explored by implementing and validating different models. An original codebase called CHAD (Coupled Hydrodynamics and Anaerobic Digestion) is extended to incorporate turbulent diffusion and validate it against results from OpenFOAM with 2D Rayleigh-Taylor Instability and lid-driven cavity simulations. The models are then tested for the applications with Anaerobic Digestion - a widely used wastewater treatment method. The findings demonstrate that the implemented models accurately capture turbulent diffusion when provided with an accurate flow field. Specifically, a minor effect of chemical turbulent diffusion on biochemical reactions within the anaerobic digestion tank is observed, while thermal turbulent diffusion significantly influences mixing. By successfully implementing turbulent diffusion models in CHAD, its capabilities for more accurate anaerobic digestion simulations are enhanced, aiding in optimizing the design and operation of anaerobic digestion reactors in real-world wastewater treatment applications.