Influence of Biofilms on Porous Media Hydrodynamics - Porous Media: Applications in Biological Systems and Biotechnology - page 203

and McCarty 2000; Thullner et al . 2002b, 2004). In this context, it is right-
fully pointed out by Thullner et al . that there are no published, theoretically-
derived hydraulic conductivity versus porosity relationships that account for
interpore connections in more than one dimension and heterogeneous biofilm
distributions (Thullner et al . 2002b).
In addition, it has been proposed to consider the importance of advective
flow within biofilms themselves. There is experimental evidence that advec-
tive flow occurs within biofilms (Stoodley et al . 1994; Debeer et al . 1994)
but until relatively recently these findings had not been included into mathe-
matical modeling approaches. It is now being suggested to model the biofilm
phase itself as a porous medium (Zhang and Bishop 1994; Nguyen et al . 2005;
Zacarias et al . 2005; Kapellos et al . 2007a,b). The inclusion of fluid flow
through the EPS matrix and biofilm microchannels has been demonstrated
to result in improved description of biofilm processes (Seifert and Engesgaard
2007; Thullner and Baveye 2008).
5.5.2 Mixed Domain (Hybrid) Models
More recently, the use of multiscale models has been described, which solve
the Navier-Stokes and Brinkman equation numerically and combine the
approach with a cellular automaton approach or Lagrangian-type simulations
of detached fragment trajectories (Kapellos et al . 2007a,b).
A hybrid Lagrangian particle dynamics model capable of describing biofilm
formation in porous media is described in detail in Chapter 7 of this topic.
Such a model might be better suited to incorporate the heterogeneity of porous
media and microbial populations, and to ultimately improve our ability to
describe hydrodynamics and mass transport in biofilm-affected porous media.
5.6 Porous Media Biofilms in Nature and Technology
Biofilms are recognized to be present in many industrial, environmental, and
medical systems. Initial work mostly focused on the eradication of biofilms
by treatment with antimicrobials, but more recently many of the “typical”
biofilm properties have been recognized to be potentially advantageous for
engineered applications (Petrozzi et al . 1993; Bouwer et al . 2000; Sauer et al .
2002; Stoodley et al . 2002b; Cvitkovitch 2004; Molin et al . 2004; Massoudieh
et al . 2007; Costerton 2007; Stewart and Franklin 2008).
Despite the fact that biofilm growth and organization are not yet com-
pletely understood (as discussed earlier), it is clear that the establishment of
organized biofilm communities can be utilized for benefit. The close proximity
of organisms to each other, allowing for the possibility of cell-cell communica-
tion, exchange of genetic elements (DNA, RNA), colocation of physiologically