Three primary strategies used separately or in conjunction to remediate most sites are:

• Destruction or alteration of contaminants.
• Extraction or separation of contaminants from environmental media.
• 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 inorganic species.

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:

• Soil, sediment, and sludge:

  - In situ biological treatment.

  - In situ physical/chemical treatment.

  - In situ thermal treatment.

  - Ex situ biological treatment (assuming excavation).

  - Ex situ physical/chemical treatment (assuming excavation).

  - Ex situ thermal treatment (assuming excavation).

  - Containment.

  - Other treatment processes.

• Ground water, surface water, and leachate:

  - In situ biological treatment.

  - In situ physical/chemical treatment.

  - Ex situ biological treatment (assuming pumping).

  - Ex situ physical/chemical treatment (assuming pumping).

  - Containment.

• Air emissions/off-gas treatment.

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.
• Availability.
• 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 MATRIX

TABLE 3-1b. DEFINITION OF SYMBOLS USED IN THE TREATMENT TECHNOLOGIES SCREENING MATRIX

Factors and Definitions	Worse	Average	Better	Other
Availability Number of vendors that can design, construct, and maintain the technology.	Fewer than 2 vendors	2-4 vendors	More than 4 vendors	Data Not Available
Contaminants Treated Contaminants are classified into the following eight groups: - Nonhalogenated VOCs; - Halogenated VOCs; - Nonhalogenated SVOCs; - Halogenated SVOCs; - Fuels; - Inorganics; - Radionuclides; - Explosives.	No Demonstrated Effectiveness at Pilot or Full Scale	Limited Effectiveness Demonstrated at Pilot or Full Scale	Effectiveness Demonstrated at Pilot or Full Scale	Level of Effectiveness highly dependent upon specific contaminant and its application/design
System Reliability /Maintainability The expected range of demonstrated reliability and maintenance relative to other effective technologies	Low reliability and high maintenance	Average reliability and average maintenance	High reliability and low maintenance	Not applicable
Cleanup Time provided that this technology is effective for this specific contaminant. 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 water.	More than 3 years for in situ soil	1-3 years	Less than 1 year	Contaminant specific
	More than 1 year for ex situ soil	0.5-1 year	Less than 0.5 year	Contaminant specific
	More than 10 years for water	3-10 years	Less than 3 years	Contaminant specific
Overall Cost 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 ($100-$300 /ton)	Less than $110/metric ton ($100/ton)	Contaminant specific
	More than $2.64/1,000 liters ($10/1,000 gal.) for ground water	$0.79-$2.64 /1,000 liters ($3.00-$10.00/ 1,000 gallons)	Less than $0.79/1,000 liters ($3.00/1,000 gallons)	Contaminant specific
	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)	Contaminant specific

Source: Remediation Technologies Screening Matrix and Reference Guide, Version I (EPA, USAF, 1993).