A Citizen’s Guide to 

Air Stripping

What Is Air Stripping?

Air stripping is the process of moving air through 

contaminated groundwater or surface water in an 

above-ground treatment system. Air stripping removes 

chemicals called “volatile organic compounds” or “VOCs.” 

VOCs are chemicals that easily evaporate, which means 

they can change from a liquid to a vapor (a gas). The 

air passing through contaminated water helps evaporate 

VOCs faster. After treating the water, the air and chemical 

vapors are collected, and the vapors are either removed 

or vented outside if VOC levels are low enough. Air 

stripping is commonly used to treat groundwater as 

part of the “pump and treat” cleanup method. (See A 

Citizen’s Guide to Pump and Treat [EPA 542-12-017].)

How Does It Work?

Air stripping uses either an air stripper or aeration tank 

to force air through contaminated water and evaporate 

VOCs. The most common type of air stripper is a 

packed-column air stripper, which is a tall tank filled with 

pieces of plastic, steel, or ceramic packing material. 

Contaminated water is pumped above ground and 

into the top of the tank and sprayed over the top of the 

packing material. The water trickles downward through 

the spaces between the packing material, forming a thin 

film of water that increases its exposure to air blown in at 

the bottom of the tank. A sieve-tray air stripper is similar 

in design but contains several trays with small holes. As 

water flows across the trays, a fan at the bottom blows 

air upwards through the holes, increasing air exposure. 

Aeration tanks are another type of design that remove 

VOCs by bubbling air into a tank of contaminated water.

Rising air and vapors accumulate at the top of the air 

stripper or aeration tank where they are collected for 

release or treatment. Treated water flows to the bottom, 

where it is collected and tested to make sure it meets 

cleanup requirements. The water may be further treated, 

if necessary, to achieve required levels. Clean water 

may be pumped back underground, into local surface 

waters, or to the municipal wastewater treatment plant.

Aeration tanks are typically shorter than packed-column 

or sieve-tray air strippers. The size and type of air 

stripper used will depend on the types and amounts of 

contaminants as well as the quantity of water requiring 

treatment. 

How Long Will It Take?

The flow of water through an air stripper or aeration 

tank may take only a few minutes, depending on the 

size of the device and the rate of water flow through it. 

However, cleanup of all the contaminated water at a site 

can take several months to years. The actual cleanup 

time will depend on several factors. For example, it will 

take longer where:

• Contaminant concentrations are high or the source 

of dissolved contaminants has not been completely 

removed.

• The amount of water requiring treatment is large.

• Groundwater cannot be pumped at a fast rate.

• Buildup of mineral deposits or algae on the packing 

material require frequent removal.

Packed-Column Air Stripper These factors vary from site to site.
United States Office of Solid Waste and EPA 542-F-12-002

Environmental Protection Emergency Response September 2012

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

www.cluin.org

Example

Air stripping is part of the 

treatment for four groundwater 

pump and treat systems 

operating at the North Indian 

Bend Wash Superfund site 

in Arizona. Groundwater at 

the site is contaminated with 

an industrial solvent called 

trichloroethene (TCE) and 

other VOCs. Contamination 

extends over an area of about 

8 square miles and to depths 

over 100 feet. 

The first pump and treat 

system began operating in 

1994. The others were added 

later to improve cleanup. The 

packed-column air strippers 

remove VOC vapors, which 

are then treated with activated 

carbon and another method 

called “ultraviolet oxidation.” 

Cleaned water is discharged 

to an area irrigation network 

and reservoir. As of 2011, over 

40,000 pounds of TCE had 

been removed, and cleanup 

of some areas was nearly 

complete. The systems are 

expected to operate for another 

40 to 70 years to clean up the 

entire site.

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.

Is Air Stripping Safe?

Air stripping is generally considered to be safe to use. Air strippers may be 

brought to the site so that contaminated water does not have to be transported 

to a cleanup facility. Contaminated water is contained throughout cleanup so that 

there is little chance for people to come into contact with it. The treated water 

usually may be returned to the groundwater or discharged to surface water. The 

chemical vapors produced by air stripping are treated, if necessary, to ensure 

unsafe levels of vapors are not released.

How Might It Affect Me?

Installation of the air stripper 

and treatment equipment 

may require use of heavy 

machinery, especially at 

large contaminated sites. 

Area neighborhoods may 

experience some increased 

truck traffic as the equipment 

is delivered. Large tanks or 

columns may be visible from 

the street and may need 

to operate for many years. 

However, care is taken to 

make sure the operation of 

air strippers is as quiet as 

possible. 

Why Use Air Stripping?

Air stripping is an effective 

way of removing VOCs from 

contaminated water and is 

commonly used as part of 

groundwater pump and treat 

systems at sites around the 

country. Air strippers can be 

brought to the site eliminating 

the need to pump contaminated 

water for offsite treatment.

Air stripper and treatment building

Sample plastic packing material. (Photo from Mass 

Transfer, Ltd.)