BIOAUGMENTATION FOR GROUNDWATER REMEDIATION: AN OVERVIEW - Bioaugmentation for Groundwater Remediation - page 2

to aid in the decision-making process such as the Decision Support Tools (http://www.frtr.gov/
decisionsupport/; accessed June 18, 2012) and the Hazardous Waste Clean-Up Information site
CLU-IN (http://clu-in.org/; accessed June 18, 2012). These software enable users to weigh the
various remediation options against the characteristics of their specific site and pollutants. One
of the technologies available for remediation is bioaugmentation (a specific type of strategy
used in implementing bioremediation). The appropriate application and control of this technol-
ogy is the subject of this volume.

1.1.2 Definitions: General Bioremediation Terminology

Due in part to the relatively low cost of biological processes, bioremediation is an
increasingly popular approach to remediation. Bioremediation is the use of organisms (usually
microorganisms) to clean up contaminated sites by degradation (breaking carbon bonds) or
transformation (changing the bond structure or redox state) of pollutants to produce nontoxic
compounds. As of 2009, bioremediation was the most common technology used to remediate
polluted soils and groundwater (Figure 1.1 ).
For simplicity, the term “degradation” will be used in this text to refer to both processes,
unless specifically stated. There are several classes of bioremediation technologies available,
such as monitored natural attenuation (MNA, which often relies heavily on natural biodegrada-
tion), biostimulation, phytoremediation and bioaugmentation. The phrase “natural attenuation”
refers to the intrinsic capacity of the environment to degrade or transforma contaminant within a
reasonable timeframe. In the United States, all possible processes can participate. In Europe,
most countries require demonstration of biological processes. As a remediation strategy, MNA
involves no overt action on the part of the remediator, but it should be monitored to ensure that
the degradation is proceeding in a timely fashionwith no undesiredmetabolites. Biostimulation is
the next step up from natural attenuation, wherein physical and/or chemical treatment enhances
the natural biodegradation (e.g., oxygen added to maintain aerobic processes). This strategy
requires careful calculation and extensive knowledge of the polluted site on the part of the
practitioner to choose the right stimulation for the organisms that already exist at the site. In
certain cases, the organisms that can degrade a target pollutant either do not exist at the site or are
not present in sufficient numbers for a “timely” treatment, and that is where bioaugmentation
might provide an advantage over the other bioremediation strategies.
Bioaugmentation is the addition of biocatalysts (generally bacteria, but it also could involve
the addition of fungi, genes or enzymes) to degrade target pollutants, either in situ or ex situ .
In most commercial applications, bioaugmentation involves the addition of mixed cultures of
bacteria that have been derived from natural environments and demonstrated to be capable
of rapid biodegradation of problematic contaminants. In rare cases, additions of genetically-
engineered microorganisms (GEMs) also have been tested, but GEMs have yet to be

7%

Bioremediation

8%

Physical methods

12%

43%

Phytoremediation

Others

Chemical methods

30%

Figure 1.1. The use of common remediation methods by percentage as of 2009 (adapted from
Pandey et al., 2009 ).