A Citizen’s Guide to

Activated Carbon Treatment

Activated carbon granules

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. 

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 

Contaminants and vapors 

sorbed to activated carbon
United States Office of Solid Waste and EPA 542-F-12-001

Environmental Protection Emergency Response September 2012

Agency (5102G) www.epa.gov/superfund/sites

www.cluin.org

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 contaminants 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 about 

this and other technologies in 

the Citizen’s Guide Series, 

visit:

www.cluin.org/remediation

www.cluin.org/products/

citguide

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.

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.