Remediation Technologies Screening Matrix, Version 4.0 4.18 Separation
(Ex Situ Soil Remediation Technology)
  Description Synonyms Applicability Limitations Site Information Points of Contact
Data Needs Performance Cost References Vendor Info. Health & Safety
Table of Contents
Technology>>Soil, Sediment, Bedrock and Sludge

>>3.5 Ex Situ Physical/Chemical Treatment

      >>4.18 Separation
Introduction>> Separation techniques concentrate contaminated solids through physical and chemical means. These processes seek to detach contaminants from their medium (i.e., the soil, sand, and/or binding material that contains them).


Figure 4-18: Typical Gravity Separation System  

The separation processes are used for removing contaminated concentrates from soils, to leave relatively uncontaminated fractions that can then be regarded as treated soil. Ex situ separation can be performed by many processes. Gravity separation and sieving/physical separation are two well-developed processes that have long been primary methods for treating municipal wastewaters. Magnetic separation, on the other hand, is a much newer separation process that is still being tested.

Gravity Separation

Gravity separation is a solid/liquid separation process, which relies on a density difference between the phases. Equipment size and effectiveness of gravity separation depends on the solids settling velocity, which is a function of the particles size, density difference, fluid viscosity, and particle concentration (hindered settling). Gravity separation is also used for removing immiscible oil phases, and for classification where particles of different sizes are separated. It is often preceded by coagulation and flocculation to increase particle size, thereby allowing removal of fine particles.

Magnetic Separation

Magnetic separation is used to extract slightly magnetic radioactive particles from host materials such as water, soil, or air. All uranium and plutonium compounds are slightly magnetic while most host materials are nonmagnetic. The process operates by passing contaminated fluid or slurry through a magnetized volume. The magnetized volume contains a magnetic matrix material such as steel wool that extracts the slightly magnetic contamination particles from the slurry.

Sieving/Physical Separation

Sieving and physical separation processes use different size sieves and screens to effectively concentrate contaminants into smaller volumes. Physical separation is based on the fact that most organic and inorganic contaminants tend to bind, either chemically or physically, to the fine (i.e., clay and silt) fraction of a soil. The clay and silt soil particles are, in turn, physically bound to the coarser sand and gravel particles by compaction and adhesion. Thus, separating the fine clay and silt particles from the coarser sand and gravel soil particles would effectively concentrate the contaminants into a smaller volume of soil that could then be further treated or disposed.

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The target contaminant groups for ex situ separation processes are SVOCs, fuels, and inorganics (including radionuclides). The technologies can be used on selected VOCs and pesticides. Magnetic separation is specifically used on heavy metals, radionuclides, and magnetic radioactive particles, such as uranium and plutonium compounds.

Physical separation often precedes chemical extraction treatment based on the assumption that most of the contamination is tied to the finer soil fraction, which alone may need to be treated. Separation is also useful when heavy metal contaminants occur as particulates (e.g., in small-arms ranges). One advantage of physical separation processes is that high throughputs can be achieved with relatively small equipment.

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Factors that may limit the applicability and effectiveness of these processes include:
  • High clay and moisture content will increase treatment cost.
  • Gravity separation processes rely on a difference in the solids and liquid phase densities. Specific gravity of particles will effect settling rate and process efficiency. Additionally, settling velocity is dependent on the viscosity of the suspending fluid, which must be known to estimate process efficiency and to size equipment.
  • Special measures may be required to mitigate odor problems, resulting from organic sludge that undergoes septic conditions.

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Data Needs:

A detailed discussion of data elements is provided in Subsection 2.2.1 (Data Requirements for Soil, Sediment, and Sludge). In addition, particle size distribution; soil type, physical form, handling properties, and moisture content; contaminant type and concentration; texture; and organic content need to be investigated.

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Performance Data:

Gravity separation and sieving/physical separation are full-scale, well-established technologies used mostly for treatment of wastewater and contaminated soil, sediment, and sludge. Magnetic separation is a promising new technique used to remove radioactive contaminants from soils. It has recently been tested at the bench-scale level at DOE sites.

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Additional cost information can be found in the Hazardous, Toxic, and Radioactive Wastes (HTRW) Historical Cost Analysis System (HCAS) developed by Environmental Historical Cost Committee of Interagency Cost Estimation Group.


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Treatment Technologies for Site Cleanup: Annual Status Report (ASR), Tenth Edition, EPA 542-R-01-004

Innovative Remediation Technologies:  Field Scale Demonstration Project in North America, 2nd Edition

Abstracts of Remediation Case Studies, Volume 4,  June, 2000, EPA 542-R-00-006

Guide to Documenting and Managing Cost and Performance Information for Remediation Projects - Revised Version, October, 1998, EPA 542-B-98-007

Nottingham Trent  University,1995. Interim Status Report, Enhancement Techniques for Ex Situ Separation Processes Particularly With Regard to  Fine Particles, Nottingham, United Kingdom, 

Battelle Memorial Institute, 1995. ReOpt. V3.1, by Battelle Memorial Institute for DOE under Contract DE/AC06/76RLO 1830.

Coyne Prenger, 1995. High Gradient Magnetic Separation (HGMS), Los Alamos National Laboratory (LANL), LALP-94-264.

DOE, April 1995. Technology Catalogue, Second Edition, Office of Environmental Management & Office of Technology Development, DOE/EM-0235.

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Site Information:

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Points of Contact:

General FRTR Agency Contacts

Technology Specific Web Sites:

Government Web Sites

Non Government Web Sites

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Vendor Information:

A list of vendors offering Ex Situ Physical/Chemical Soil Treatment is available from EPA REACH IT which combines information from three established EPA databases, the Vendor Information System for Innovative Treatment Technologies (VISITT), the Vendor Field Analytical and Characterization Technologies System (Vendor FACTS), and the Innovative Treatment Technologies (ITT), to give users access to comprehensive information about treatment and characterization technologies and their applications.

Government Disclaimer

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Health and Safety:

Hazard Analysis

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