MSc Defence: Multi-Scale Model Formulation of a Porous Medium Biofilm Reactor and the Effects of Diffusion, Attachment, and Detachment on Reactor Performance

CANDIDATE: Emma Bottomley

ABSTRACT: We derive a one-dimensional macroscopic model for biofilm formation in a porous medium reactor to investigate the role of tangential diffusion of substrate and suspended bacteria on reactor performance. By comparing an existing base model - one without tangential diffusion that was the point of departure for our work, to a new model - which includes tangential diffusion, we noticed significant changes in system dynamics. Our results suggest that neglecting it can underestimate quenching length and biofilm accumulation downstream, even in the advection dominated regime. The study was extended to include also a 2-dimensional model for biofilm formation in a porous medium reactor. The effects of attachment and detachment of suspended bacteria were also examined in both dimensions. In the one-dimensional model, it was found that attachment has a stronger influence on substrate depletion, which becomes more pronounced as diffusion in the pore space increases. The 2-dimensional model found that incorporating suspended bacteria and its processes is crucial for accurately describing biofilm formation in porous media, especially in clean bed simulations. This thesis provides insights into improving biofilm reactor modeling, emphasizing the importance of incorporating tangential diffusion in one-dimensional models and accurately characterizing biomass exchange mechanisms in all cases.