A Citizen's Guide to
Activated Carbon Treatment
What Is Activated Carbon Treatment?
Activated carbon is a material used to filter harmful
chemicals from contaminated water and air. It is
composed of black granules of coal, wood, nutshells
or other carbon-rich materials. As contaminated water
or air flows through activated carbon, the contaminants
sorb (stick) to the surface of the granules and are
removed from the water or air. Granular activated
carbon or "GAC" can treat a wide range of contaminant
vapors including radon and contaminants dissolved in
groundwater, such as fuel oil, solvents, polychlorinated
biphenyls (PCBs), dioxins, and other industrial
chemicals, as well as radon and other radioactive
materials. It even removes low levels of some types of
metals from groundwater.
How Does It Work?
Activated carbon treatment generally consists of one or
more columns or tanks filled with GAC. Contaminated
water or vapors are usually pumped through a column
from the top down, but upward flow is possible. As the
contaminated water or air flows through the GAC, the
contaminants sorb to the outer and inner surfaces of
the granules. The water and air exiting the container
will be cleaner. Regular testing of exiting water or air is
conducted to check contaminant levels. If testing shows
that some contaminants remain, the water or air may
need to be treated again to meet the treatment levels.
^Contaminants and Vapors
Activated Carbon
Pores
Activated carbon granules
Contaminants and vapors
sorbed to activated carbon
The GAC will need to be replaced when the available
surfaces on the granules are taken up by contaminants
and additional contaminants can no longer sorb to them.
The "spent" GAC may be replaced with fresh GAC or
"regenerated" to remove the sorbed contaminants. To
regenerate spent GAC, it is usually sent to an offsite
facility where it is heated to very high temperatures to
destroy the contaminants. If a lot of GAC needs to be
regenerated, equipment to heat the GAC and remove
the sorbed contaminants can be brought to the site.
Depending on the site, treated groundwater may
be pumped into a nearby stream or river or back
underground through injection wells or trenches. At
some sites, a sprinkler system can distribute the water
over the ground surface so that it seeps into soil. The
water also may be discharged to the public sewer
system for further treatment at a sewage treatment
plant.
How Long Will It Take?
It only takes a few minutes for water or vapors to
pass through an activated carbon filter. However, the
time it takes to clean up a site with activated carbon
treatment will depend on how long it takes to bring all
the contaminated groundwater or contaminant vapors
to the ground surface for treatment. This can take
several months to many years. Treatment may take
longer where:
• Contaminant concentrations are high or the
source of dissolved contaminants has not been
completely removed.
• The volume of contaminated groundwater or
vapors is large.
• Treatment of groundwater or vapors involves
several other cleanup methods.
These factors vary from site to site.
Is Activated Carbon Treatment Safe?
Activated carbon treatment is safe to use. Treated
water is sampled and analyzed regularly to ensure that
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the carbon continues to adequately sorb contaminants. If concentrations start
to increase in the treated water, the carbon is reactivated or replaced. The tanks
are cleaned or replaced with care to avoid releasing contaminants. Larger filters
are often preferred because they do not have to be replaced as often as small
ones. When treatment is complete, the used carbon may contain hazardous
contaminants that require special handling and disposal at a hazardous waste
facility.
How Might It Affect Me?
Activated carbon treatment generally will not disrupt the surrounding community.
Initial construction of systems to extract groundwater or contaminant vapors
from the ground may involve the use of heavy equipment. This may cause a
temporary increase truck traffic in the neighborhood as equipment is brought
to the site or when carbon tanks are exchanged. However, the treatment
system itself is not particularly noisy while running. Depending on the amount
of groundwater or vapors that need to be treated, tanks of activated carbon can
range in size from a 55-gallon drum to a tank that is 20 feet tall and 10 feet or
more in diameter.
Why Use Activated Carbon Treatment?
Activated carbon is the most commonly used approach to treating groundwater
in "pump and treat" systems (See A Citizen's Guide to Pump and Treat [EPA
542-F-12-017]). It is also used to treat contaminant vapors removed from
contaminated soil and groundwater by soil vapor extraction and other cleanup
methods. (See A Citizen's Guide to Soil Vapor Extraction [EPA 542-F-12-018].)
Activated carbon units can be brought to the site and set up relatively quickly.
Large groundwater treatment system
with five tanks of activated carbon.
Small groundwater treatment system with two tanks of
activated carbon.
Example
Disposal of chemical wastes at
the Conservation Chemical
Company Superfund site in
Missouri contaminated the soil
and groundwater with solvents,
waste oil, PCBs, and pesticides.
A pump and treat system began
operating in 1991 to keep the
contaminated groundwater from
moving offsite. The pumped
water is being treated with a
series of cleanup methods. One
of the last treatment steps is the
use of two columns of activated
carbon to remove any remaining
contaminants.
Water exiting the activated carbon
columns is sampled weekly for
metals and quarterly for PCBs,
pesticides, and other contami-
nants to ensure the system
is working. The columns are
refilled with reactivated carbon
when they can no longer remove
contaminants adequately. The
system uses about 240,000
pounds of activated carbon each
year. Sampling of groundwater
continues to show that the system
is protecting human health and
the environment, and the treated
water is discharged to the nearby
Missouri River.
For More Information
For more information on this
and other technologies in the
Citizen's Guide Series, contact:
U.S. EPA
Technology Innovation &
Field Services Division
Technology Assessment Branch
(703)603-9910
NOTE: This fact sheet is intended solely as general 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.
United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
(5102G)
EPA 542-F-12-001
September 2012
www.epa.gov/superfund/sites
www.cluin.org
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