I (7
Unrted States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
EPA/542/F-92/009
March 1992
&EPA
A Citizen's Guide to Using
Indigenous And Exogenous
Microorganisms In Bioremediation
Technology Innovation Office.
.Technology Fact Sheet
CONTENTS
Page
What is
Biofemedlatlon?
What Are indigenous
And Exogenous
Microorganisms?
How Are Indigenous
Microorganisms Used?
How Are Exogenous
Microorganisms Used?
Which Sites Are
Appropriate For
Indigenous And/Or
Exogenous
Microorganisms?
For More Information
What Is Bioremediation?
Bioremediation uses naturally occurring
microorganisms (yeast, fungi and/or
bacteria) to degrade — break down —
hazardous substances into less toxic or
nontoxic substances. Microorganisms,
just like humans, eat and digest organic
substances for nutrients and energy.
Certain microorganisms can digest
organic substances that are hazardous to
humans. The organic contaminants
degrade into harmless products
consisting mainly of carbon dioxide and
water. Some examples of organic
contaminants include fuels, such as oil
spills, and solvents.
Microorganisms must thrive in order for
bioremediation to take place. In
addition to the food source provided by
the organic contaminants, some
microorganisms require additional
nutrients. To help the microorganisms
survive, several bioremediation
technologies have been developed. The
specific bioremediation technology used
is determined by the type of micro-
organisms present, as well as the site
conditions. The types of micro-
organisms present are an important
consideration because different
microorganisms degrade different types
of compounds and survive under
different conditions.
What Are Indigenous
And Exogenous
Microorganisms?
Indigenous microorganisms are those
microorganisms which are native to the
site. To stimulate the growth of these
indigenous microorganisms, the soil
conditions, such as temperature, pH,
and oxygen and nutrient content, may
need to be adjusted.
If the microorganisms needed to
degrade the contaminant are not present
in the soil, microorganisms from other
locations, whose effectiveness has been
tested in laboratories, are added to the
contaminated soil. These are called
exogenous microorganisms. The soil
conditions sometimes need to be
adjusted to ensure that the exogenous
microorganisms will thrive.
U.S. Environmental Protection Agency
Region 5. Library CPI .i?i
d, 12th Fla
indigenous and Exogenous Microorganisms Profile Chicago, \L 60604V
Indigenous microorganisms are already present at the site to degrade the organic contaminants into
nonhazardous substances.
Exogenous microorganisms are not native to the site. These microorganisms can be cultured, in a lab or
on site, to degrade contaminants.
Produced by the
Superfund Program
Printed on Recycled Paper
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What Other Industries Use
Microorganisms?
to addition to degrading hazardous substances,
microorganisms have a long history of use fay a
variety of industries. For example, the medical
Industry uses a fungus to produce the antibiotic
penicillin, which Is used to destroy harmful
bacteria. Hie beer industry uses yeast during
the fermentation process to make alcoholic
beverages.
^/
How Are Indigenous Microorganisms
Used?
Figure 1, below, illustrates the use of both indigenous and
exogenous microorganisms. In most sites undergoing
bioremediation, indigenous microorganisms are used. The
process begins by sampling the contaminated soil. These
samples are taken to a laboratory and studied. In the
laboratory, the types of microorganisms present in the
contaminated soil and their optimal living conditions are
determined. If the indigenous microorganisms are able to
successfully degrade the contaminant, exogenous micro-
organisms are not needed.
If the soil conditions are right, the indigenous micro-
organisms will use the contaminants in the soil as a food
source and convert them to nonhazardous substances. The
main end products of this conversion reaction are carbon
dioxide and water (CO2+ Hf>). In order to see if the
bioremediation reaction is indeed occurring, the level of end
products (CO2+ HjO) is monitored for an increase in levels
and the contaminants are checked for a decrease in levels.
If die reaction is not occurring, the soil conditions may need
adjusting.
Once the degradation of the contaminants is completed,
most of the indigenous microorganisms will die because
they have used all of their food source. The dead micro-
organisms pose no contamination risk because they have
already degraded the contaminants into nontoxic substances.
How Are Exogenous Microorganisms
Used?
As with indigenous bioremediation, the first step in this
process is soil sampling. The samples are taken to a
laboratory and studied. Here, the types of microorganisms
are identified. If microorganisms capable of degrading the
contaminants are not present, then exogenous micro-
organisms may be considered for introduction into the soil.
Figure 1
Use of Indigenous and Exogenous Microorganisms
WgOr f*
tract Soil /
Extract Soil
Samples
•
mlnant (e.g. oil)
6559
Obtain And Culture
Useful Microorganisms
Add Useful Exogenous
Microorganisms to Soil
^
Useful Organism*
Not Present
Examine Samples
For Indigenous
Microorganisms And
Environmental
Conditions
Useful Indigenous
Microorganisms
Present In The Soil
BIOREMEDIATION OCCURS IN THE SOlp
Microorganism* Eat Oil
Microorganisms Digest Oil
and Convert tt To COj * Hj O
Mterooganlsma /
ExcreMCOj+HiO /
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However, the toxicity of the soil needs to be determined to
ensure that the exogenous organisms will survive. Although
they are not naturally present at the contaminated site, these
exogenous microorganisms are naturally occurring at other
locations.
The exogenous microorganisms are taken from other
locations and 'cultured' in the laboratory. This means the
microorganisms are placed in optimal living conditions (for
example, perfect temperatures and an abundant source of
nutrients) so that they can multiply. When they have
multiplied to great numbers, these microorganisms can be
taken to the site and added to the contaminated soil.
If the soil conditions are right, the indigenous micro-
organisms will use the contaminants in the soil as a food
source and convert them to nonhazardous substances. The
main end products of this conversion reaction are carbon
dioxide and water (CO2 + Hf>). In order to see if the
bioremediation reaction is indeed occurring, the level of end
products (CO2+ HjO) is monitored for an increase in levels
and the contaminants are checked for a decrease in levels.
If the reaction is not occurring, the soil conditions may need
adjusting.
Once the degradation of the contaminants is completed,
most of the exogenous microorganisms will die because
they have used all of their food source. The dead micro-
organisms pose no contamination risk because they have
already degraded the contaminants into nontoxic substances.
Exogenous microorganisms will not permanently affect the
soil's composition.
S~ "" "' " -X.
What is An Innovative Treatment
Technology?
Trvafmertf technologies are processes applied
to the treatment of hazardous waste or
contaminated materials to permanently alter
their condition through chemical, biological, or
physical means. Technologies that have been
tested, selected or used for treatment of
hazardous waste or contaminated materials but
lack well-documented cost and performance
data under a variety of operating conditions are
called Innovative treatment technologies.
Are Genetically Engineered
Microorganisms Befog Used?
The genetic engineering of microorganisms for
bioremediation Is still in the research and
development stages and has not yet been used
commercially in the United States. As the
knowledge and uaes of genetic engineering
Increase, it may be an important way to enhance
bioremediation technology. Uses of genetically
engineered microorganisms for bioremediation
ere regulated by the Toxic Substances Control
Act
x, s
Which Sites Are Appropriate For
Indigenous And/Or Exogenous
Microorganisms?
Indigenous bioremediation, exogenous bioremediation, or a
combination of the two can be useful depending upon site
conditions. Relying on indigenous microorganisms is
appropriate if useful strains are present and concentrated in
the area of contamination. If indigenous organisms are
already surviving in the original soil conditions, the process
of optimizing the soil's conditions for these microorganisms
is not as complicated as it is for exogenous microorganisms.
Using indigenous microorganisms also tends to be less
expensive than culturing and introducing exogenous micro-
organisms into the soil. For all of these reasons, most
bioremediation technologies make use of indigenous micro-
organisms whenever possible. However, exogenous micro-
organisms are needed when useful microorganisms are not
already present
A thorough scientific assessment of the contaminated soil
and the soil conditions must be performed to determine
whether indigenous or exogenous microorganisms would
make the bioremediation more effective.
U.S. Environmental Protection Agency
Region 5, Library ;pL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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For More Information
EPA prepared this fact sheet to provide baste Information on Indigenous and exogenous microorganisms.
Additional technical reports are listed below. The document wltti a "PB" designation is available by contact*
big the National Technical information Service (NTISJat 1-800-336-4700. Mall orders can be sent to:
National Technical information Service
Springfield, VA 22161
Other documents may be obtained by contacting:
Center for Environmental Research Information
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513)569-7562
There may be a charge for these documents.
* Btoremedlatlon of Contaminated Surface Soil, PB90-164047.
• Engineering Bulletin-Slurry Bfodegradatton, EPA/540/2-90/016.
• Understanding Bioremediation: A Guide Book for Citizens, EPA 540/2-91/002.
NOTICE: This fact sheet is intended solely as general guidance and information. It is not intended, nor can it be relied upon, to create any rights enforceable by any
party in litigation with the United States. The Agency also reserves trie right to change this guidance at any time without public notice.
4 -fru S. GOVERNMENT PRINTING OFFICE. 1992 - 648-080/40192
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