PRODUCTION AND HANDLING OF DEHALOCOCCOIDES BIOAUGMENTATION CULTURES - Bioaugmentation for Groundwater Remediation - page 88

CHAPTER 3
PRODUCTION AND HANDLING
OF DEHALOCOCCOIDES BIOAUGMENTATION
CULTURES
Robert J. Steffan and Simon Vainberg
Shaw Environmental, Inc., Lawrenceville, NJ 08648
3.1 INTRODUCTION
Chlorinated ethenes have been used extensively as industrial solvents and cleaning agents,
and improper disposal practices and accidental spills have led to them becoming common
groundwater contaminants throughout the United States and the world (Moran and Zogorski,
2007 ; Westrick et al., 1984 ). Treatment of chlorinated solvent contamination has involved the
use of a wide range of technologies including soil vapor extraction, air sparging, chemical
oxidation or reduction, in situ thermal treatment, and biological oxidation or reduction.
Currently, the most common treatment alternative for these compounds is biological degrada-
tion facilitated by either stimulating indigenous dechlorinating organisms or adding cultures of
exogenous microorganisms enriched especially for this task. Adding exogenous organisms is
commonly referred to as bioaugmentation.
Although the use of bioaugmentation has a long history for treating challenging pollutants,
overselling of the technology as a panacea for pollutant remediation and underperformance of
some commercial products led to a period of low acceptability of this technology for remedial
activities. In many cases, the lack of acceptance of the technology was justified because the
addition of microbes to contaminated environments did not improve remediation beyond what
could be achieved by stimulating indigenous microbial populations (DeFlaun and Steffan, 2002 ;
Unterman et al., 2000 ). In the case of remediating chlorinated solvent contaminated aquifers,
the technology was limited to aerobic cometabolism that was challenged by poor transport of
the biocatalysts, an inability of the microbes to use the contaminant as a growth substrate, the
need to maintain aerobic conditions, the production of toxic intermediates, and the inability to
degrade some important solvents (most notably perchloroethene [PCE]) (Steffan et al., 1999 ).
The success of early applications of Dehalococcoides spp. ( Dhc ) containing consortia for
in situ remediation of chlorinated solvent contaminated aquifers has led to a renewed interest in
bioaugmentation because the added cultures reproduced in situ , were transported well through
the treated aquifer, and improved bioremediation performance (Ellis et al., 2000 ; Major et al.,
2002 ). The fact that the cultures did not require oxygen to degrade the contaminants made them
easy to transport and apply, and only a fermentable carbon source was needed to support their
growth and degradative activity. To date, several hundred bioaugmentation applications have
been performed to remediate chlorinated solvent contaminated aquifers.
3.1.1 Microbial Cultures Used for Bioaugmentation
The predominant biodegradation pathway used for chlorinated ethene remediation in
contaminated aquifers is anaerobic reductive dehalogenation. During reductive dechlorination,