Three primary strategies used separately or in conjunction to
remediate most sites are:
- Destruction or alteration of contaminants.
- Extraction or separation of contaminants from
- Immobilization of contaminants.
Treatment technologies capable of contaminant destruction
by altering their chemical structure are thermal, biological, and
chemical treatment methods. These destruction technologies can be
applied in situ or ex situ to contaminated media.
Treatment technologies commonly used for extraction and
separation of contaminants from environmental media include
soil treatment by thermal desorption, soil washing, solvent
extraction, and soil vapor extraction (SVE) and ground water
treatment by either phase separation, carbon adsorption, air
stripping, ion exchange, or some combination of these
technologies. Selection and integration of technologies should
use the most effective contaminant transport mechanisms to arrive
at the most effective treatment scheme. For example, more air
than water can be moved through soil. Therefore, for a volatile
contaminant in soil that is relatively insoluble in water, SVE
would be a more efficient separation technology than soil
flushing or washing.
Immobilization technologies include stabilization,
solidification, and containment technologies, such as placement
in a secure landfill or construction of slurry walls. No
immobilization technology is permanently effective, so some type
of maintenance is desired. Stabilization technologies are often
proposed for remediating sites contaminated by metals or other
These concepts about site remediation strategies and
representative technologies associated with them are summarized
in Figure1: Classification
of Remedial Technologies by Function. One feature obvious
from the figure is that the choice of applied technologies is not
extensive once a strategy is selected.
Generally, no single technology can remediate an entire site.
Several treatment technologies are usually combined at a single
site to form what is known as a treatment train. SVE can be
integrated with ground water pumping and air stripping to
simultaneously remove contaminants from both ground water and
soil. The emissions from the SVE system and the air stripper can
be treated in a single air treatment unit. An added benefit is
that the air flow through the soil stimulates or enhances natural
biological activity, and some biodegradation of contaminants
occurs. In some cases, air is injected into either the saturated
or the unsaturated zones to facilitate contaminant transport and
to promote biological activity.
For the purpose of this document, the technologies are
separated into 14 treatment groups as follows:
These 14 treatment groups correspond to the following 14
subsections (3.1 through 3.14). The discussion of the broad
application of each treatment group (e.g., in situ biological
treatment for soil, sediment, bedrock and sludge) in this section is
followed by a more detailed discussion of each treatment
technology (e.g., bioventing) in that treatment group, in Section 4. Information on
completed projects in these treatment process areas has been
presented in tables extracted from the Treatment Technologies for Site
Cleanup: Annual Status Report Tenth Edition (February 2001), and the Synopses
of Federal Demonstrations of Innovative Site Remediation
Technologies, FRTR, 1993.
Tables 3-1 and 3-2
summarize pertinent information for each of the treatment
technologies presented in Section 4. Information summarized includes the following:
- Technology Profile Number (refers to Section 4).
- Developmental Status (full scale vs. pilot scale).
- Typical Treatment Train.
- Residuals Produced.
- O&M or Capital Intensive.
- Contaminants Treated.
- System Reliability/Maintainability.
- Cleanup Time.
- Overall Cost.
Additionally, a brief description of each treatment technology
is presented at the beginning of each process description.
TABLE 3-1a. DEFINITION OF
LEGENDS USED IN THE TREATMENT TECHNOLOGIES SCREENING
Scale status of an available technology.
Full scale: technology has been used in real site
Pilot Scale: studies conducted in the field or
the laboratory to fine-tune the design of the technology.
Is the technology only effective as part of the
Technology must be used with the combination of other
technologies as a treatment train.
Technology can be used as a stand alone one.
Residuals need to be treated.
|O&M or Capital
Main cost intensive parts.
Operation and Maintenance Intensive
Both O&M and Capital Intensive
Neither O&M or Capital Intensive
DEFINITION OF SYMBOLS USED IN THE TREATMENT TECHNOLOGIES
Number of vendors that can design, construct, and
maintain the technology.
|Fewer than 2 vendors
||More than 4 vendors
||Data Not Available
Contaminants are classified into the following eight
- Nonhalogenated VOCs;
- Halogenated VOCs;
- Nonhalogenated SVOCs;
- Halogenated SVOCs;
Demonstrated Effectiveness at Pilot or Full Scale
Demonstrated at Pilot or Full Scale
Demonstrated at Pilot or Full Scale
||Level of Effectiveness
highly dependent upon specific contaminant and its application/design
The expected range of demonstrated reliability and maintenance
relative to other effective technologies
|Low reliability and high
||Average reliability and
||High reliability and low
provided that this technology is effective for this specific
Time required to clean up a "standard" site
using the technology. The "standard" site is
assumed to be 20,000 tons (18,200 metric tons) for soils
and 1 million gallons (3,785,000 liters) for ground
|More than 3 years for in
||Less than 1 year
|More than 1 year for ex situ
||Less than 0.5 year
|More than 10 years for water
||Less than 3 years
Design, construction, and operations and maintenance
(O&M) costs of the core process that defines each
technology, exclusive of mobilization, demobilization,
and pre- and post-treatment. For ex situ soil, sediment,
and sludge technologies, it is assumed that excavation
costs average $55.00/metric ton ($50/ton). For ex situ
ground water technologies, it is assumed that pumping
costs average $0.07/1,000 liters ($0.25/1,000 gallons).
|More than $330/metric ton
($300/ton) for soils
||$110-$330 /metric ton
||Less than $110/metric ton
|More than $2.64/1,000 liters
($10/1,000 gal.) for ground water
||$0.79-$2.64 /1,000 liters
|Less than $0.79/1,000 liters
|More than $11.33/kg ($25/lb)
for air emissions and off-gases
||$3.17-$11.33 /kg ($7-$25/lb)
||Less than $3.17/kg ($7/lb)
Source: Remediation Technologies Screening
Matrix and Reference Guide, Version I (EPA, USAF, 1993).