Dynamical simulation of a continuous stirred tank bioreactor with the use of cellular automata for the biofilm description

Abstract

The paper concerns mathematical modeling and simulation of a continuous-flow stirred tank bioreactor (CSTBR) in which heterogeneous biofilm forms on its walls. The mathematical model couples a 2D cellular-automata biofilm model with differential equations describing the liquid phase in the bioreactor. Double-substrate aerobic phenol biodegradation by Pseudomonas putida bacteria was chosen as a process example. The influence of key process parameters on the dynamical characteristics of the bioreactor and the biofilm structure evolution during the process was investigated. Such an analysis has not been previously performed. It was shown that cell death strongly affects both biofilm heterogeneity and the technological properties of the bioreactor. Neglecting this phenomenon leads to improper design of the bioreactor. The influence of substrate load on the heterogeneity of the biofilm was evaluated in the process limited by two substrates. So far only a single substrate limitation has been evaluated in this regard. Even for large carbonaceous substrate concentrations, the biofilm growth and its structure are influenced by oxygen depletion. It was shown that an increased detachment rate increases bioreactor productivity.