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.



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