Integrated Modeling of Anaerobic Fluidized Bed Bioreactor for Deicing Waste Treatment. I: Model Derivation

An integrated mathematical model for propylene glycol (PG) degradation in an anaerobic fluidized bed bioreactor is described. Special attention is put on biomass distribution, bed expansion, and bed segregation, associated with the biofilm accumulation process. In order to interpret the segregation of the bed during the initial development of the biofilm, the model postulates various mixing intensities along the bed height and thereby different exchange rates of microbial cells between the biofilm and the bulk liquid. The model incorporates stoichiometry of PG methanization, hydrodynamics, and reaction kinetics for elucidating microscopic interaction among microbial trophic groups inside the biofilm as well as the macroscopic behavior of the reactor such as bed expansion. A biofilm diffusion mechanism is also taken into account focusing on the spatial distribution of multiple species of micro-organisms. Employing moving boundaries makes the model flexible in computation, which permits simplifying the implementation of the biofilm accumulation and the bed expansion phenomena.