Modelling the structure and function of extracellular polymeric substances in biofilms with new numerical techniques

Abstract

The objective of this study is the mathematical description of the structure and function of the extracellular polymeric substances (EPS) in biofilms. The basic assumptions of the EPS biofilm model are:the production of EPS in biofilms is coupled to the growth of micro-organismsthe production of EPS is additionally coupled to the substrate conditions-the EPS represent a considerable volume fraction of the matrix in biofilms and thus the density of the biofilms is strongly influenced by the EPS-sorption of biocides and pollutants in biofilms occurs mainly to EPSthe EPS can be used as an energy source during substrate limited phases. The mathematical model has been derived as a system of partial differential equations. The numerical solution of these complex balance equations has been done by a self-adaptive Galerkin-h-p-method. It can be shown, that on the one hand the simulation of substrate conversion and biofilm growth with the EPS-biofilm model yields similar results as the known biofilm models without consideration of the EPS fraction. On the other hand the advantage of the EPS-biofilm model is a better understanding of biofilm structure, which is mainly influenced by the EPS fraction in the biofilm. Furthermore, the sorption of pollutants, such as heavy metals and chlorinated organic substances, can be simulated in more detail.