Influence of Biofilms on Porous Media Hydrodynamics - Porous Media: Applications in Biological Systems and Biotechnology - page 174

5.6.2 Deep Subsurface Biofilms for Enhanced Oil Recovery

and Carbon Sequestration .......................................... 208

5.6.3 Porous Media Biofilm Reactors in Industry and Waste

Treatment ........................................................... 209

5.7 Conclusions and Outlook ................................................... 210

5.8 References ................................................................... 211

5.1 Introduction and Overview
Microbial biofilms form in natural and engineered systems and can signifi-
cantly affect the hydrodynamics in porous media. Microbial biofilms develop
through the attachment and growth of microorganisms, which encase them-
selves in self-produced extracellular polymeric substances (EPS). Microbial
biofilms are, in general, more resistant to environmental stresses, such as
mechanical stress, temperature, pH, and water potential fluctuations, than
planktonic cells. Biofilm growth in porous media influences porosity, perme-
ability, dispersion, diffusion, and mass transport of reactive and nonreactive
solutes. Understanding and controlling biofilm formation in porous media will
maximize the potential benefit and will minimize the detrimental effects of
porous media biofilms. Subsurface remediation, enhanced oil recovery, and car-
bon sequestration are only a few examples of beneficial porous media biofilm
applications.

5.2 An Introduction to Biofilms
Microbial biofilms have probably been known to exist for as long as we have
known about microorganisms. When Anthony van Leeuwenhoek described
the “scuff” (plaque) from his teeth in 1683 (see http://www.ucmp.berkeley.
edu/history/leeuwenhoek.html [accessed Jan. 09, 2009] or Dixon 2009), the
discovery of these “many very little living animalcules, very prettily
a-moving,” i.e., the mere existence of microorganisms, overshadowed the
fact that they were associated with a surface, that is, the teeth. It might
be due to the fact that microorganisms associated with surfaces are very
dicult to study that the scientific community almost exclusively focused
on the study of free-floating (“suspended” or “planktonic”) microorganisms
well into the twentieth century. The importance of attached microorgan-
isms in nature and engineered systems was really not described until the
end of the 1970s when Characklis and Costerton et al . clearly described
the abundance of biofilms in many environments (Characklis 1973a,b;
Costerton et al . 1978). Bill Characklis' legacy to the biofilm field was recently