United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
(5102G)
&EPA A Citizen's Guide
to Bioremediation
EPA 542-F-01-001
April 2001
www.epa.gov/superfund/sites
www.cluin.org
The Citizen's Guide Series
EPA uses many methods to clean up pollution at Superfund and other sites. Some, like bioremediation, are
considered new or innovative. Such methods can be quicker and cheaper than more common methods. If you
live, work, or go to school near a Superfund site, you may want to learn more about cleanup methods. Perhaps
they are being used or are proposed for use at your site. How do they work? Are they safe? This Citizen's Guide
is one in a series to help answer your questions.
What is bioremediation?
Bioremediation allows natural processes to clean up harmful chemicals in the environment.
Microscopic "bugs" or microbes that live in soil and groundwater like to eat certain harmful
chemicals, such as those found in gasoline and oil spills. When microbes completely digest
these chemicals, they change them into water and harmless gases such as carbon dioxide.
Microbe eats oil
Microbe digests oil and changes
it to water and harmless gases
Microbe releases
water and harmless
gases into soil or
groundwater
How does it work?
In order for microbes to clean up harmful chemicals, the right temperature, nutrients (fertiliz-
ers), and amount of oxygen must be present in the soil and groundwater. These conditions
allow the microbes to grow and multiply—and eat more chemicals. When conditions are not
right, microbes grow too slowly or die. Or they can create more harmful chemicals. If
conditions are not right at a site, EPA works to improve them. One way they improve
conditions is to pump air, nutrients, or other substances (such as molasses) underground.
Sometimes microbes are added if enough aren't already there.
The right conditions for bioremediation cannot always be achieved underground. At some
sites, the weather is too cold or the soil is too dense. At such sites, EPA might dig up the soil
to clean it above ground where heaters and soil mixing help improve conditions. After the soil
is dug up, the proper nutrients are added. Oxygen also may be added by stirring the mixture
or by forcing air through it. However, some microbes work better without oxygen. With the
right temperature and amount of oxygen and nutrients, microbes can do their work to
"bioremediate" the harmful chemicals.
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For more
information
write the Technology
Innovation Office at:
U.S.EPA(5102G)
1200 Pennsylvania Ave.,
NW
Washington, DC 20460
or call them at
(703) 603-9910.
Further information also
can be obtained at
www.cluin.org or
www.epa.gov/
superfund/sites.
Sometimes mixing soil can cause harmful chemicals to evaporate before the microbes can eat
them. To prevent these chemicals from polluting the air, EPA mixes the soil inside a special tank
or building where chemicals that evaporate can be collected and treated.
Microbes can help clean polluted groundwater as well as soil. To do this, EPA drills wells and
pumps some of the groundwater into tanks. Here, the water is mixed with nutrients and air
before it is pumped back into the ground. The added nutrients and air help the microbes
bioremediate the groundwater. Groundwater can also be mixed underground by pumping
nutrients and air into the wells.
Once harmful chemicals are cleaned up and microbes have eaten their available "food," the
microbes die.
Is bioremediation safe?
Bioremediation is very safe because it relies on microbes that naturally occur in soil. These mi-
crobes are helpful and pose no threat to people at the site or in the community. Microbes them-
selves won't hurt you, but never touch the polluted soil or groundwater—especially before eating.
No dangerous chemicals are used in bioremediation. The nutrients added to make microbes
grow are fertilizers commonly used on lawns and gardens. Because bioremediation changes the
harmful chemicals into water and harmless gases, the harmful chemicals are completely de-
stroyed. To ensure that bioremediation is working, EPA tests samples of soil
and groundwater.
- How long will it ?
The time it takes to bioremediate a site depends on several factors:
• types and amounts of harmful chemicals present
• size and depth of the polluted area
• type of soil and the conditions present
• whether cleanup occurs above ground or underground
These factors vary from site to site. It can take a few months or even several years for
microbes to eat enough of the harmful chemicals to clean up the site.
Why use bioremediation?
EPA uses bioremediation because it takes advantage of natural processes. Polluted soil and
groundwater can be cleaned at the site without having to move them somewhere else. If the right
conditions exist or can be created underground, soil and groundwater can be cleaned without
having to dig or pump it up at all. This allows cleanup workers to avoid contact with polluted soil
and groundwater. It also prevents the release of harmful gases into the air. Because microbes
change the harmful chemicals into water and harmless gases, few if any wastes are created.
Often bioremediation does not require as much equipment or labor as most other methods.
Therefore, it is usually cheaper. Bioremediation has successfully cleaned up many polluted sites
and is being used at 50 Superfund sites across the country.
NOTE: Tto fact sheet is intended solely as general guidance and information to the public. It is not intended, nor can it be relied
upon, to create any rights enforceable by any party in litigation with the United States, or to endorse the use of products or services
provided by specific vendors. The Agency also reserves the right to change this fact sheet at any time without public notice.
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