BIOAUGMENTATION FOR GROUNDWATER REMEDIATION: AN OVERVIEW - Bioaugmentation for Groundwater Remediation - page 6

time before the onset of complete dechlorination (ESTCP, 2005 ; Lendvay et al., 2003 ; Major
et al., 2002 ; Maes et al., 2006 ; Hood et al., 2008 ). The use of Dehalococcoides spp. for
bioaugmentation is discussed later in this chapter and is a primary focus of this volume. This
technique represents a remarkable success story for bioaugmentation, partly because it is based
on a rare combination of circumstances: (1) the limited distribution, abundance or capacity of
organisms mediating complete dehalorespiration; (2) the widespread problem of groundwater
contamination with halogenated solvents, especially the chlorinated ethenes; and (3) the ability
of dehalorespiring organisms to survive and colonize the subsurface after additions of
fermentable substrates and establishment of anaerobic conditions.

1.3 TYPES OF BIOAUGMENTATION
Once the decision is made to use bioaugmentation, there are several variations available, as
summarized in Figure 1.3 . The choice of strategy depends on the site parameters and the
pollutant of interest. Bioaugmentation also can be used in combination with other remediation
strategies. The following sections discuss the benefits and drawbacks of the various types of
bioaugmentation. The types of bioaugmentation are divided into two categories: those that are
currently practiced and those that are still in the experimental stages. Current bioaugmentation
practices are discussed briefly below and in detail in other chapters in this volume. Potential
future bioaugmentation strategies also are discussed.

1.3.1 Currently Practiced Methods

Most of the commercial bioaugmentation that is currently practiced relies on the application
of microorganisms, or those options in the cell bioaugmentation category. The variations
discussed in this section represent only some of the potential bioaugmentation technologies.

1.3.1.1 Preadapted Bacterial Strains or Consortia
Among the more successful bioaugmentation techniques has been the use of preadapted
bacterial strains or consortia. These strains can be isolated or enriched from other contaminated
sites. However, if the site of interest already has the capacity to degrade the pollutant, though not at

Cell
Bioaugmentation

Plant
Bioaugmentation

Gene
Bioaugmentation*

Pre-adapted bacterial strain
OR
Pre-adapted bacterial consortium
OR
Genetically engineered microorganisms*
OR
Commercial i n oculum

Phytoaugmentation

Bacterial carriers of
mobile genetic
elements*

Naked genetic
material*

Activat ed soil

Rhizoremediation

Contaminated
soil or water
matrix

Biofilms

Figure 1.3. Summary of different bioaugmentation methods. * denotes methods that are yet to be
commercially practiced.