f/EPA
United States
Environmental Protection
Agency
EPA/540/M5-89/003
April 1989
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
In-Situ Vacuum Extraction
Terra Vac, Inc.
TECHNOLOGY DESCRIPTION: This in-situ
vacuum extraction technology is a process for the
removal and venting of volatile organic compounds
(VOCs) from the vadose or unsaturated zone of soils.
Often, these compounds can be removed from the
vadose zone before they have a chance to
contaminate groundwater. In using this technology,
subsurface organic contaminants are "vacuumed up"
via a well, vapor/liquid separated, and then exposed
to activated carbon before the "vapor" is allowed to
be released into the atmosphere.
The technology uses readily available components
such as extraction and monitoring well(s), manifold
piping, vapor/liquid separator, vacuum pump, and
emission control equipment, such as activated carbon
canisters. Once a contaminated area is completely
defined, an extraction well (or wells) is installed
(depending upon the extent of contamination) and is
connected by piping to a vapor/liquid separator device
(Figure 1). A vacuum pump draws the subsurface
contaminants through the well, separator device, and
an activated carbon canister before discharge of the
air streams is allowed to the atmosphere. Subsurface
vacuum and soil vapor concentration are monitored
via vadose zone monitoring wells.
The technology does not require highly trained
operators or soil excavation, and it also is not depth
limited. The technology works best when it is applied
towards the remediation at sites which are
contaminated by liquids having high vapor pressures.
However, the process is limited in applicability;
diffusion rates through dense soils (such as
compacted clays) are much lower than through sandy
soils, and if activated carbon is used, then spent
carbon must be processed. In addition, depending on
the soil type and the depth to groundwater, the radius
of influence of a single extraction well can range from
tens to hundreds of feet. Typical contaminant
recovery rates also range between 20 and 2500
pounds per day and are a function of volatility of the
organic compound recovered. Therefore, the more
volatile the organic compound, the faster the process
works. The developer also states that the process is
more cost effective where contaminated soils are
predominantly above the water table, although
systems have been designed for vapor and
groundwater recovery.
WASTE APPLICABILITY: This technology is
applicable to organic compounds that are highly
volatile at ambient temperatures in soils and
groundwater.
s
/
Primary
Activatrrl
Carbon
Canisters
Figure 1. Process diagram for in-situ vacuum
extraction.
-------
vvEPA
United States
Environmental Protection
Agency
EPA/540/M5-89/003
April 1989
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
In-Situ Vacuum Extraction
Terra Vac, Inc.
TECHNOLOGY DESCRIPTION: This in-situ
vacuum extraction technology is a process for the
removal and venting of volatile organic compounds
(VOCs) from the vadose or unsaturated zone of soils.
Often, these compounds can be removed from the
vadose zone before they have a chance to
contaminate groundwater. In using this technology,
subsurface organic contaminants are "vacuumed up"
via a well, vapor/liquid separated, and then exposed
to activated carbon before the "vapor" is allowed to
be released into the atmosphere.
The technology uses readily available components
such as extraction and monitoring well(s), manifold
piping, vapor/liquid separator, vacuum pump, and
emission control equipment, such as activated carbon
canisters. Once a contaminated area is completely
defined, an extraction well (or wells) is installed
(depending upon the extent of contamination) and is
connected by piping to a vapor/liquid separator device
(Figure 1). A vacuum pump draws the subsurface
contaminants through the well, separator device, and
an activated carbon canister before discharge of the
air streams is allowed to the atmosphere. Subsurface
vacuum and soil vapor concentration are monitored
via vadose zone monitoring wells.
The technology does not require highly trained
operators or soil excavation, and it also is not depth
limited. The technology works best when it is applied
towards the remediation at sites which are
contaminated by liquids having high vapor pressures.
However, the process is limited in applicability;
diffusion rates through dense soils (such as
compacted clays) are much lower than through sandy
soils, and if activated carbon is used, then spent
carbon must be processed. In addition, depending on
the soil type and the depth to groundwater, the radius
of influence of a single extraction well can range from
tens to hundreds of feet. Typical contaminant
recovery rates also range between 20 and 2500
pounds per day and are a function of volatility of the
organic compound recovered. Therefore, the more
volatile the organic compound, the faster the process
works. The developer also states that the process is
more cost effective where contaminated soils are
predominantly above the water table, although
systems have been designed for vapor and
groundwater recovery.
WASTE APPLICABILITY: This technology is
applicable to organic compounds that are highly
volatile at ambient temperatures in soils and
groundwater.
s
/
Primary
Activatrd
Carbon
Canisters
Figure 1. Process diagram for in-situ vacuum
extraction.
------- |