Biomedical Engineering Reference
In-Depth Information
chlorinated ethenes are used as electron acceptors by naturally adapted bacteria, and the
process results in a chlorine atom on the chlorinated compound being removed and replaced
with a hydrogen atom. Sequential dechlorination of PCE most commonly proceeds to trichlor-
oethene (TCE),
cis
-1,2-dichloroethene (
cis
-DCE), vinyl chloride (VC) and finally the desired end
product, ethene. In some bacteria,
trans
-1,2-DCE or 1,1-DCE (Zhang et al.,
2006
) are the
predominant TCE dechlorination products.
Although biodegradation of chlorinated ethenes often can be performed by naturally
occurring microorganisms that use endogenous resources to support contaminant degradation
(i.e., intrinsic bioremediation) or nutrients that are purposefully added to support their activity
(i.e., biostimulation), some aquifers lack an indigenous microbial population capable of
completely dechlorinating the contaminants. This lack of an adequate microbial population
capable of completely dechlorinating PCE and TCE to ethene can sometimes lead to the
accumulation of
cis
-DCE and VC (Hendrickson et al.,
2002
), which are more toxic than the
parent compounds. Consequently, the addition of exogenous organisms (i.e., bioaugmentation)
is sometimes used to supplement the indigenous microbial population.
While many dechlorinating microorganisms have been identified, only bacteria of the genus
Dhc
have been shown to completely reduce PCE and TCE to ethene (Maym ´ -Gatell et al.,
1997
;
He et al.,
2003a
,
b
). These organisms use molecular hydrogen as an obligate electron donor and
halogenated compounds as obligate respiratory electron acceptors. Acetate is typically used by
Dhc
as a carbon source. Studies of field sites have strongly correlated the presence of
Dhc
strains with complete dehalogenation of chlorinated ethenes
in situ
(Hendrickson et al.,
2002
).
Therefore, microbial cultures used to augment chlorinated solvent contaminated groundwater
contain at least one strain of the
Dhc
. A list of some known suppliers of bioaugmentation
cultures for chlorinated solvents is presented in Table
3.1
.
Because of the difficulty of growing
Dhc
-type organisms in pure culture (Maym
´
-Gatell
et al.,
1999
; He et al.,
2003a
,
b
), consortia containing
Dhc
, fermentative bacteria and other
microbes that support the growth and activity of the
Dhc
strains are used for remedial
applications (Ellis et al.,
2000
; Lendvay et al.,
2003
; Major et al.,
2002
). The consortia, and
the
Dhc
therein, can be grown using a wide range of carbon sources that are fermented to
Table 3.1. List of Known U.S. Vendors of Dhc-Containing Bioaugmentation Cultures
Vendor
Culture Name
Contact Information
FMC Corp.
Dechlorination culture
815-235-3503;
http://environmental.fmc.com/
BCI, Inc.
BCI-e
617-923-0976;
http://www.bcilabs.com
Environmental Bio-
Systems, Inc.
Dechlorination culture
415-381-5195;
http://www.ebsinfo.com/
BAC-9
TM
EOS Remediation, LLC
888-873-2204;
http://www.eosremediation.com/
JRW Bioremediation, LLC
Dechlorination culture
913-438-5544;
http://www.jrwbioremediation.com
Redox Tech, LLC
RTB-1
919-678-0140;
http://www.redox-tech.com/
Regenesis
Bio-Dechlor INOCULUM
®
PLUS(+)
949-366-8000;
http://www.regenesis.com
SDC-9
TM
, Hawaii-05
TM,
PJKS
TM
Shaw Environmental, Inc.
SiREM Labs
KB-1
®
519-822-2265;
http://www.siremlab.com
Terra Systems, Inc.
TSI DC bioaugmentation
culture
TM
302-798-9553;
http://www.terrasystems.net
Web sites in Table 3.1 were last accessed May 2012
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