Hierarchical Simulation of the Spatiotemporal ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Hierarchical Simulation of the Spatiotemporal Evolution of Heterogeneous Biofilms and their Impact on the Flow Pattern and Mass Transport in 3-D Porous Media
Author:George Kapellos <gek222@chemeng.upatras.gr> (PhD Student)
Terpsichori Alexiou <xalexiou@chemeng.upatras.gr> (PhD Student)
Stavros Pavlou <sp@chemeng.upatras.gr> (Professor)
Alkiviades Payatakes <acp@terpsi.iceht.forth.gr> (Professor)
Presenter:George Kapellos <gek222@chemeng.upatras.gr> (PhD Student)
Date: 2006-06-18     Track: General Sessions     Session: General

A computer-aided simulator has been developed for the prediction of the pattern of evolution and the rate of growth of heterogeneous biofilms within the pore space of 3-D virtual porous media (core-scale). The biofilm itself is considered as a heterogeneous porous material that exhibits a hierarchy of length scales. A recently developed theoretical model, which takes into account fundamental geometric and physicochemical properties of the biofilm at the cell- and molecular-scales, is used to calculate the values of the local hydraulic permeability and diffusion coefficient within it. Modified Navier-Stokes-Brinkman equations are solved numerically to determine the velocity and pressure fields within the pore space, which is occupied partly by free fluid and partly by biofilms. Under the action of large fluid shear stresses biofilm fragments detach and re-enter into the free fluid stream. A Lagrangian-type simulation is used to determine the trajectories of the detached fragments until they exit from the system or re-attach to downstream grain or biofilm surfaces. Furthermore, the spatiotemporal distributions of nutrients and soluble cellular products are determined from the numerical solution of the governing convection-diffusion-reaction equations. The simulator incorporates growth and apoptosis kinetics for the bacterial cells and production and lysis kinetics for the extracellular polymeric substances that compose the biofilm. Growth-induced deformation of the biofilms is implemented by using a cellular automaton approach. Transient changes in the pore geometry caused by biofilm proliferation intensify the formation of preferential flowpaths within the porous medium. The decrease of permeability caused by clogging of the porous medium is calculated and is found to be in qualitative agreement with published experimental results.