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Remediation Technologies Screening Matrix, Version 4.0 4.46 Granulated Activated Carbon (GAC)
(Ex Situ GW Remediation Technology)
  Description Synonyms Applicability Limitations Site Information Points of Contact
Data Needs Performance Cost References Vendor Info. Health & Safety
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>>3.12 Ex Situ Physical/Chemical Treatment (assuming pumping)

      >>4.46 Granulated Activated Carbon (GAC)/Liquid Phase Carbon Adsorption
Introduction>> Ground water is pumped through a series of canisters or columns containing activated carbon to which dissolved organic contaminants adsorb. Periodic replacement or regeneration of saturated carbon is required.

Description:

Figure 4-46:
Typical Fixed-Bed Carbon Adsorption System  

Liquid phase carbon adsorption is a full-scale technology in which ground water is pumped through one or more vessels containing activated carbon to which dissolved organic contaminants adsorb. When the concentration of contaminants in the effluent from the bed exceeds a certain level, the carbon can be regenerated in place; removed and regenerated at an off-site facility; or removed and disposed. Carbon used for explosives- or metals-contaminated ground water probably cannot be regenerated and should be removed and properly disposed. Adsorption by activated carbon has a long history of use in treating municipal, industrial, and hazardous wastes.

The two most common reactor configurations for carbon adsorption systems are the fixed bed (see figure) and the pulsed or moving bed. The fixed-bed configuration is the most widely used for adsorption from liquids. Pretreatment for removal of suspended solids from streams to be treated is an important design consideration. If not removed suspended solids in a liquid stream may accumulate in the column, causing an increase in pressure drop. When the pressure drop becomes too high, the accumulated solids must be removed, for example, by backwashing. The solids removal process necessitates adsorber downtime and may result in carbon loss and disruption of the mass transfer zone.

Modification of GAC, such as silicone impregnated carbon, could increase removal efficiency and extend the length of operation. It may also be safer to regenerate.

The duration of GAC is usually short-term; however, if concentrations are low enough, the duration may be long-term. The duration of operation and maintenance is dependent on contaminant type, concentration, and volume; regulatory cleanup requirements; and metal concentrations.

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Synonyms:

Activated carbon; Carbon filtration.
DSERTS Code: F20 (Carbon Absorption)

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Applicability:

The target contaminant groups for carbon adsorption are hydrocarbons, SVOCs and explosives. Limited effectiveness may be achieved on halogenated VOCs and pesticides. Liquid phase carbon adsorption is effective for removing contaminants at low concentrations (less than 10 mg/L) from water at nearly any flow rate, and for removing higher concentrations of contaminants from water at low flow rates (typically 2 to 4 liters per minute or 0.5 to 1 gpm). Carbon adsorption is particularly effective for polishing water discharges from other remedial technologies to attain regulatory compliance. Carbon adsorption systems can be deployed rapidly, and contaminant removal efficiencies are high. Logistic and economic disadvantages arise from the need to transport and decontaminate spent carbon.

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Limitations:

The following factors may limit the applicability and effectiveness of the process:
  • The presence of multiple contaminants can impact process performance. Single component isotherms may not be applicable for mixtures. Bench tests may be conducted to estimate carbon usage for mixtures.
  • Streams with high suspended solids (> 50 mg/L) and oil and grease (> 10 mg/L) may cause fouling of the carbon and may require frequent treatment. In such cases, pretreatment is generally required.
  • Costs are high if used as the primary treatment on wastestreams with high contaminant concentration levels.
  • Type, pore size, and quality of the carbon, as well as the operating temperature, will impact process performance. Vendor expertise for carbon selection should be consulted.
  • Carbon used for explosives- or metals-contaminated ground water is not regenerated.
  • Highly Water-soluble compounds and small molecules are not adsorbed well.
  • All spent carbon eventually need to be properly disposed.

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Data Needs:

A detailed discussion of these data elements is provided in Subsection 2.2.2 (Data Requirements for Ground Water, Surface Water, and Leachate).

The major design variables for liquid phase carbon applications are empty bed contact time (EBCT), usage rate, and system configuration. Particle size and hydraulic loading are often chosen to minimize pressure drop and reduce or eliminate backwashing. System configuration and EBCT have an impact on carbon usage rate. When the bed life is longer than 6 months and the treatment objective is stringent (ratio of effluent concentration,Ce, to influent concentration, Co, <0.05), a combination of single beds operating in parallel is preferred. For a single adsorber, the EBCT is normally chosen to be large enough to minimize carbon usage rate. When less stringent objectives are required (Ce/Co<0.3), blending of effluents from partially saturated adsorbers can be used to reduce carbon replacement rate. When stringent treatment objectives are required (Ce/Co<0.05) and bed life is short (less than 6 months), multiple beds in series may be used to decrease carbon usage rate.

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Performance Data:

Adsorption by activated carbon has a long history of use as a treatment for municipal, industrial, and hazardous wastestreams. The concepts, theory, and engineering aspects of the technology are well developed. It is a proven technology with documented performance data. Carbon adsorption is a relatively nonspecific adsorbent and is effective for removing many organic, explosive, and some inorganic contaminants from liquid and gaseous streams.

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Cost:

Costs associated with GAC are dependent on wastestream flow rates, type of contaminant, concentration of contaminant, mass loading, required effluent concentration, and site and timing requirements. Costs are lower with lower concentration levels of a contaminant of a given type. Costs are also lower at higher flow rates. At flow rates of 0.4 million liters per day (0.1 mgd), costs increase to $0.32 to $1.70 per 1,000 liters ($1.20 to $6.30 per 1,000 gallons) treated.

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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References:

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

DOE, 1994. Technology Application Analysis: Petroleum Product Recovery and Contaminated Groundwater Remediation Amoco Petroleum Pipeline Constantine, MI, prepared by Stone & Webster Environmental Technology & Services.

DOE, 1994. Technology Application Analysis: Recovery of Free Petroleum ProductFort Drum, Fuel Dispensing Area 1595 Watertown, New York, prepared by Stone & Webster Environmental Technology & Services.

EPA, 1986. Mobile Treatment Technologies for Superfund Wastes, EPA/540/2-86/003.

EPA, 1990. Innovative and Alternative Technology Assessment Manual, EPA, Office of Water Program Operations, EPA/430/9-78/009.

EPA, 1993. Approaches for the Remediation of Federal Facility Sites Contaminated with Explosive or Radioactive Wastes, EPA/625/R-93/013.

Federal Remediation Technologies Roundtable, 1995. Remediation Case Studies: Groundwater Treatment, EPA/542/R-95/003.

Zappi, M.E., B.C. Fleming, and C.L. Teetar, 1992. "Draft - Treatability of Contaminated Groundwater from the Lang Superfund Site", USAE-WES.

Zappi, M.E., C.L. Teeter, B.C. Fleming, and N.R. Francingues, 1991. "Treatability of Ninth Avenue Superfund Site Groundwater", WES Report EL-91-8.

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Site Information:

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Points of Contact:

General FRTR Agency Contacts

Technology Specific Web Sites:

Government Web Sites

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Vendor Information:

A list of vendors offering Ex Situ Physical/Chemical Water 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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