Activated carbon (AC)-based technology involves emplacement of AC-based amendments for in situ remediation of soil and groundwater (Fan et al., 2017; EPA, 2018). Besides AC, amendments typically include other reactive products (Table 1) commonly used with in situ remediation technologies, such as in situ chemical reduction (ISCR), in situ chemical oxidation (ISCO), and bioremediation. The technology is commonly referred to as "carbon-based injectate" (CBI), especially for remediation of petroleum hydrocarbons. To differentiate these products from other organic carbon-based amendments frequently used for in situ remediation of chlorinated solvents, EPA refers to the technology as activated carbon-based technology.

AC-based amendments remove contaminant via two processes: adsorption by AC and degradation by reactive amendments. Adsorption results in rapid initial removal of contaminants from the aqueous phase, whereas degradation subsequently destroys contaminants. The synergy between adsorption and degradation, either biotic or abiotic, has been investigated in numerous bench-scale studies.

The coupling of adsorption and degradation makes this technology a promising remedial option for addressing persistent plumes emanating from contaminants sorbed on soil, residual non-aqueous phase liquid (NAPL), or mass stored in low-permeability zones (EPA, 2018). Such plumes are commonly encountered at geologically complex sites and are shown to be recalcitrant to conventional treatment, including pump and treat and other amendment-based technologies such as ISCO. The technology might also be applicable near or at the source area, especially when combined with other source treatment remedies, to limit contaminant mass flux out of source zones to downgradient plumes.

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Additional Information

Biofilm Processes in Biologically Active Carbon Water Purification
Simpson D.R.
Water Research. 42:2839-2848 (2008) [Abstract]

This review paper describes the composition and activity of a biologically active carbon (BAC) biofilm used in water purification and reviewed the ability of BAC to remove and biodegrade organic contaminants. The hypotheses for improved contaminant degradation by BAC were proposed and discussed.

Community Guide to Granular Activated Carbon Treatment
EPA 542-F-21-010, 2021

The Community Guide series (formerly Citizen's Guides) is a set of two-page fact sheets describing cleanup methods used at Superfund and other hazardous waste cleanup sites. Each guide answers six questions about the method: 1) What is it? 2) How does it work? 3) How long will it take? 4) Is it safe? 5) How might it affect me? 6) Why use it?

Current State of In Situ Subsurface Remediation by Activated Carbon-Based Amendments
Fan D, Gilbert E.J. and Fox T.
Journal of Environmental Management. 204:793-803 (2017) [Abstract]

This publication presents an independent analysis of both the scientific and practical aspects of AC-based remedial technology for in situ remediation by gathering and synthesizing the scientific knowledge and practical lessons from a broad range of contaminant removal processes involving adsorption and/or degradation.

Effect of Chloroethene Concentrations and Granular Activated Carbon on Reductive Dechlorination Rates and Growth of Dehalococcoides spp.
Aktaş Ö., Schmidt K.R., Mungenast S., Stoll C., and Tiehm, A.
Bioresource Technology. 103:286-292 (2012) [Abstract]

This bench-scale study investigated the effects of granular activated carbon on dechlorination activity of Dehalococcoides spp. in the presence of high concentration of tetrachloroethene (PCE), which simulates the toxicity threshold for biological dechlorination typically observed in the presence of DNAPL. The results showed adsorption of contaminant onto activated carbon reduces the toxicity of high dissolved phase PCE concentration to Dehalococcoides spp.

Effects of Activated Carbon on Reductive Dechlorination of PCBs by Organohalid Respiring Bacteria Indigenous to Sediments
Kjellerup B.V., Naff C., Edwards S.J., Ghosh U., Baker J.E., and Sowers K.R.
Water Research 52:1-10 (2014) [Abstract]

This bench-scale research investigated the effects of activated carbon amendment in sediment on biological dechlorination of PCBs. A shift in microbial community to putative organohalide-respiring phylotypes was observed as a result of activated carbon amendment. This corresponds to more extensive dechlorination of higher chlorinated PCB congeners to less chlorinated congeners that are more susceptible to complete mineralization by aerobic PCB degrading bacteria.

Effects of Aging and Oxidation of Palladized Iron Embedded in Activated Carbon on the Dechlorination of 2-Chlorobiphenyl
Choi H., Al-Abed S. R., and Agarwal, S.
Environmental Science & Technology. 43:4137-4142 (2009) [Abstract]

This bench-scale study investigated degradation of 2-chlorobiphenyl by activated carbon embedded with palladized nano zero valent iron (nZVI). The persistence and longevity of degradation activity was specifically examined by looking at the effects of aging and oxidation of iron.

Final Report — Phase I: Application of Biofilm-Covered Activated Carbon Particles as a Microbial Inoculum Delivery System for Enhanced Bioaugmentation of PCBs in Contaminated Sediment
SERDP Project ER-2135 (September 2013)

Phase I of this project tested the proof of principle for the biofilm based delivery system in the presence of sorptive surface to enhance the biodegradation rate and extent of PCBs in contaminated sediment.

Recent Trends in In-Situ Hydrocarbon Remediation — Treatment with Activated Carbon Remedial Fluid
Herrington, T. and A. Punsoni. | Environmental Services Association of Alberta (ESAA) Weekly Webinar Series, 41 slides, 19 May 2020

Slide presentation includes three case studies describing the use PetroFix™, a solid sorbent suspended in an aqueous liquid, to treat petroleum hydrocarbons (BTEX, TPH-G, TPH-D, MTBE, naphthalene, etc) in groundwater. PetroFix involves the patented use of micro-scale activated carbon and contains nitrate and sulfate electron acceptors. Treatment occurs through a combination of in situ sorption and in situ enhanced bioremediation.

Remedial Technology Fact Sheet — Activated Carbon-Based Technology for In Situ Remediation
EPA 542-F-18-001, April 2018

This fact sheet provides information to practitioners and regulators for a better understanding of the science and current practice of AC-based remedial technologies for in situ applications. The uncertainties associated with the applications and performance of the technology are also discussed.

Synthesis of Granular Activated Carbon/Zerovalent Iron Composites for Simultaneous Adsorption/dechlorination of Trichloroethylene
Tseng H.H., Su J.G., and Liang C.
Journal of Hazardous Material. 192:500-506 (2011) [Abstract]

This bench-scale research investigated degradation of trichloroethene (TCE) by coupled adsorption and abiotic dechlorination using a composite consisting of activated carbon coated with nZVI. Based on chloride production rate, it was shown that adsorption onto activated carbon enhances the degradation rate of TCE.

Technology Update & Review - Activated Carbon for Contaminant Control and Site Remediation
Pare, J. | Smart Remediation, 4 February, virtual, 24 slides, 2021

This presentation reviews the principles around the use of activated carbon in situ and how the technology can be used to remediate organic contaminants in soil and groundwater, including field application and drawbacks and limitations. Real-life case studies are included that identify some of the major considerations in screening, selecting, designing, implementing, and monitoring a full-scale treatment project.

The Promise And Pitfalls of In-Situ Carbon Immobilization of PFAS — Two Case Studies From Michigan
Mankowski, L. | PFAS: Beyond the Theoretical and What's Working Seminar, 27 Feb, Madison, WI, 38 slides, 2020

Performance monitoring testing was conducted for three pilot tests that involved in situ carbon-based stabilization of PFAS. Two pilot tests used biochars in the PFAS source area surrounding a former tannery. In one test area, Bioavailable Absorbent Media (BAM)-Ultra™ was injected into the saturated system. After 7 days, PFOS concentrations in groundwater declined by 19-96%. In the second test area, BAM-X™ biochar was separately mixed into a 10x10 ft area. At 7 days post-mixing, groundwater PFOS concentrations reduced by 97%. At an airfield site, PlumeStop^® and PlumeStop Stout™ were injected into a co-located, low-level PCE plume downgradient of a former fire-training area. Two months post-injection, PFOS and PCE were not detected in downgradient groundwater. Neither amendment tested achieved homogenous distribution when delivered by injection. Performance monitoring is ongoing. Data have not yet demonstrated amendment effectiveness in stabilizing PFAS in soil or groundwater. However, the data will provide long-term, site-specific case studies for consideration in future feasibility studies to address PFAS. Additional information: Camp Grayling Airfield project

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