United States
                      Environmental Protection
                          Office of
                          Solid Waste and
                          Emergency Response
               March 1992
A Citizen's  Guide To
Air  Sparging
Technology Innovation Office
                                          .Technology Fact Sheet


 What Is Air Sparging?   1

 How Does tt Work?     1
 Why Consider Air
 Sparging?           2
 Will Air Sparging Work
 At Every Site?        3
 Where Is Air Sparging
 Being Used?         3
 for More Information   3
         What Is Air Sparging?

      Air sparging is an innovative
      treatment technology that injects
      air into the saturated zone (that
      part of the subsurface that is
      soaked with ground water) to
      remove hazardous contaminants.
      The air is injected below the
      contaminated area, forming
      bubbles that rise and carry
      trapped and dissolved contam-
      inants into the unsaturated zone
      (that part of the subsurface
      located above the ground water).
      Through a subsequent treatment
      technology, soil vapor extraction,
      the contaminants can be
      removed and treated as
      necessary.  (See, at right, a brief
      discussion on "What Is Soil
      Vapor Extraction?") Since air
      sparging effectively moves the
      contaminants upward into the
      unsaturated zone, this technology
      is typically used in conjunction
      with soil vapor extraction.
   What Is Soil Vapor

   Soil vapor extraction Is an
   effective treatment
   technology that can be used
   to treat volatile organic
   compounds (VOCs) in the
   unsaturated zone. This
   technology uses a vacuum to
   draw air through
   underground wells to
   vaporize the VOCs found in
   the soil. When soil vapor
   extraction Is used alone, it
   has limited effectiveness in
   treating contaminants that
   exist in the saturated zone.
V	/
How Does It Work?

Figure  1, on the following page,
provides a schematic diagram of
the air sparging process. The
process begins by installing air
injection wells into the ground
water below the contaminants.
The number of wells installed at
a site is determined by the size of
                                                            ; Fnwonmental Protecti
                                    Afr Sparging Profile    V WerU^H t r.         „..
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      Extends the effectiveness of soil vapor extraction to include contaminants that exist in ground water.

      Allows hazardous wastes to be treated on site.

      Provides an oxygen source which may stimulate bloremedlatlon of some contaminants.
 Produced by the
Supezfund Program
                                               Printed on Recycled Paper

                                           Figure 1
                    Cross-Section Of An Air Sparging/Vapor Extraction System
Air Injectl
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Soil Gas Well 1
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/ Vacuum Pump
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Illllll 1
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the contaminated area and by various geological
and engineering considerations.

One or more air compressors are used to force air
down the injection well and out through a
screened opening, causing bubbles to form.  The
bubbles move upward and outward.  The bubbles
dislodge trapped contaminants, vaporize dissolved
contaminants, and carry them up to the
unsaturated zone.

As the volatile organic compound (VOC) vapors
reach the unsaturated zone, they are pulled into
vapor extraction wells that are screened in this
zone. The air sparging treatment process is
designed and operated in conjunction with the soil
vapor extraction system to ensure VOCs are
properly removed to the surface for treatment.

The performance of air sparging is monitored in
two ways. The first measures the contaminants
that are emitted by the vapor extraction system to
ensure the VOCs are properly captured and
treated. The second method involves installing
monitoring wells and surface monitors within and
around the contaminated area to determine if
additional collection and treatment processes are
needed. These two monitoring systems are
operated simultaneously.

Air sparging provides an oxygen source which
may stimulate bioremediation of some
contaminants. Bioremediation is an innovative
treatment technology that uses microorganisms,
such as bacteria, to break down organic
contaminants into harmless substances.

Why Consider Air Sparging?

There are several advantages to using air sparging
as a treatment method. Air sparging:

    •   Extends the effectiveness of soil vapor
       extraction to include volatile contaminants
       that exist in the saturated zone

    •   Allows hazardous wastes to be treated on-

    •   Can potentially provide a quick and
       effective means of ground water clean-up
       for VOCs.

Will Air Sparging Work At Every Site?

All waste types and site conditions are not similar.
Each site must be individually investigated and
tested. Engineering and scientific judgement must
be used to determine if a technology is
appropriate for a site.

Air sparging is only useful at sites that contain
soils and other characteristics that can be
effectively treated by soil vapor extraction.  In
addition, for air sparging to be successful, soils in
the saturated zones must allow the injected air to
readily escape into the ground water. Coarse
grained soils such as sand and gravel particles
allow greater movement than fine grained soils,
such as silt and clay. Air sparging, therefore, will
work fastest at sites where there are coarse
grained soils. The most common contaminants
treated by this technology are VOCs such as:
trichloroethane, trichloroethylene, benzene,
toluene, ethylbenzene, and xylene.

Where Is Air Sparging Being Used?

Air sparging was first used as a remediation
technology in Germany in 1985 to enhance the
clean-up of ground water contaminated with
chlorinated solvents. Currently, air sparging is
widely practiced at hazardous waste sites
throughout Europe.  In the United States air
sparging has been used on a limited basis at
Superfund sites.  It has been used most often to
treat underground gasoline tank spills.
             What is An Innovative
            Treatment Technology?

       Tntttmnt 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.
    For More Information

    EPA prepared this fact sheet to provide basic Information on air sparging. Additional technical reports and
    articles are listed below. The first document can be obtained by telephone or written request to:

                      Center for Environmental Research Information
                      26 West Martin Luther King Drive
                      Cincinnati, OH 45268
                      (513) 569-7562

    The others may be available through your local library.  There may be a charge for the EPA document.

       •   The Superfund Innovative Technology Evaluation Program: Technology Profiles, EPA/540/5-91/008.

           Oroundwafer Monitoring Review. "Application of in Situ Air Sparging as an innovative Soils and
           Groundwater Remediation Technology," Spring 1992. Article by Michael C. Martey.

       •   The Hazardous Waste Consultant. "Air Sparging Improves Effectiveness of Soil Vapor Extraction
           Systems," March/April 1991.
                                                           U.S. Environmental Protection Agency
                                                           Region 5, Ucrary (PL-12J)
                                                           /7 West Jackson Boulevard, 12th Floor
                                                          Chicago,  IL  60604-3590
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 the right to change this guidance at any time without public notice.
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