BIOAUGMENTATION FOR GROUNDWATER REMEDIATION: AN OVERVIEW - Bioaugmentation for Groundwater Remediation - page 3

commercially-successful augmentation agents. Bioaugmentation also could be beneficial when
a mixture of pollutants must be degraded by a mixture of specific bacteria. It does not refer to
the addition of plant species (phytoremediation), although the two techniques can work well
together as exemplified by rhizoremediation, which is discussed later.
1.1.3 Chapter Overview
This chapter aims to establish the fundamentals of bioaugmentation, from which the reader
can then put into context the remainder of this volume. This volume focuses on the use of
bioaugmentation for chlorinated solvent remediation in groundwater, but its uses are not
limited to these compounds. We will discuss the history, status and prospects for bioaugmenta-
tion in environmental remediation in general, focusing on the key issues that influence the
practice and potential for the technology to improve the effectiveness and/or reduce the costs
for in situ bioremediation. It is intended to serve as an introduction to the remaining chapters
and an overview of the technology for the general audience. The reader will be referred to
different chapters for further elaboration on the ideas and concepts presented.
1.2 DEVELOPMENT OF BIOAUGMENTATION
FOR GROUNDWATER BIOREMEDIATION
1.2.1 Historical Development of Bioaugmentation
The idea of adding microbes to perform reactions is an ancient technology, such as the use
of microbial inocula to make fermented beverages like beer and wine, and dairy products such
as cheese and yogurt (Singer et al., 2005 ). Bioaugmentation also has been used more recently in
agriculture, with the addition of nitrogen-fixing bacteria to rhizospheres and the manipulation
of bacteria to encourage plant growth, control pathogens and improve soil structure (van Veen
et al., 1997 ; Gentry et al., 2004 ). Bioaugmentation for pollutant removal evolved from earlier
bioremediation efforts, which focused on eliminating physical and chemical barriers to the
degradation of the targeted pollutant(s) by indigenous microorganisms. The largest initial
biostimulation successes were most often those associated with straightforward removal of
environmental limitations (such as the lack of oxygen) and relied on the presence of large
numbers of native microorganisms capable of degrading the targeted compound(s). For
example, the treatment of petroleum hydrocarbons, such as those found in gasoline and diesel,
often used pumping techniques to circulate oxygen and other nutrients through the subsurface
where the indigenous bacteria were capable of degrading the contaminants (e.g., the Raymond
Process) (Raymond, 1976 ).
The concept of adding bacteria to polluted media stems from the use of bacteria in compost
piles and septic tanks, such as when bacteria were used in the early 1980s to target the
degradation of pollutants in wastewater systems (Goulding et al., 1988 ). Bioaugmentation for
treating contaminated soils and groundwater was initially considered in the 1980s and early
1990s, with the growing acceptance of bioremediation to treat petroleum hydrocarbons and
wood preserving wastes. The increasing use and perceived deficiencies of in situ bioremedia-
tion led to a proliferation of vendors offering microbial inoculants to improve groundwater
and soil bioremediation. By 1992, there were at least 75 bioaugmentation cultures available
commercially for in situ bioremediation.
Most of these inoculants were composed of common soil microorganisms grown under
aerobic conditions, and there was generally little characterization of these microbial cultures.