Influence of Biofilms on Porous Media Hydrodynamics - Porous Media: Applications in Biological Systems and Biotechnology - page 209

demonstrated the utility of biofilms in sandstone cores to reduce the perme-
ability by more than 95% at elevated pressures (8.9 MPa) and moderate tem-
peratures (32 ◦ C). Biofilm organisms under these conditions were also demon-
strated to survive exposure to scCO 2 and maintain the decreased permeability
of the core even under starvation conditions.
5.6.3 Porous Media Biofilm Reactors in Industry
and Waste Treatment
Other industrial and environmental systems and applications in which porous
media biofilms play a significant role are mostly related to water and waste
treatment.
Attached microorganisms in water filtration, which can form within, at
the influent, or euent of filtration devices, can have detrimental or ben-
eficial effects on water treatment processes. Obviously, excessive microbial
growth can reduce the hydraulic conductivity of filtration devices and result in
increased maintenance requirements, reduced run times, increased frequency
of backflushing cycles, or increased need to exchange filter materials. How-
ever, porous media biofilms have also been observed to facilitate the sorption
or degradation of organic particulates and solutes as well as the oxidative
precipitation of problem metals, such as reduced iron and manganese, during
drinking water treatment.
The use of trickling filters and infiltration systems in wastewater treat-
ment has been practiced for a long time and microorganisms, more or less
immobilized in porous media, have been used for the removal of wastewater
constituents. Both, large-scale applications of these technologies as well as
fundamental research assessing the role of biofilms in these technologies are
ongoing (Ileri and Muslu 1996; Iliuta and Larachi 2004; Wanko et al. 2005,
2006; Mauclaire et al. 2006).
Some of the characteristics discussed earlier, such as enhanced resistance
to adverse conditions and enhanced-metabolic capabilities of biofilm commu-
nities, have also led to an increased use of immobilized microbial communities
in hazardous waste treatment. The treatment of synthetic dyes or tannery
wastewater in fixed-bed biofilm reactors are two examples of such processes
(Song et al. 2003; Tse and Yu 2003).
Gas-phase treatment using biofilters has also been practiced for an
extended period of time, especially for the control of odors, such as hydro-
gen sulfide, and volatile organic compounds, such as methanol or acetone.
While such technologies are already being applied on the industrial scale
(Shareefdeen and Baltzis 1994; Kennes and Thalasso 1998; Shareefdeen et al .
2002; Elmrini et al . 2004), fundamental research targeted at understanding
the physico- and biochemical processes controlling the eciency of such vapor-
filtration devices is ongoing (Hwang et al . 1997; Tang et al . 1997; Wani et al .
1997; Ramirez et al . 2008). Overall, biofilm processes in unsaturated porous
media have been studied much less extensively than in saturated porous media