The in situ treatment of TCE and PFAS in groundwater within a silty sand aquifer

McGregor, Rick; Zhao, Ye

doi:10.1002/rem.21675

Cited by 16 publications

(24 citation statements)

References 20 publications

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“…The in-situ treatment of emerging compounds of concern such as per and polyfluoroalkyl substances (PFAS), synthetic dyes and synthetic musks have become a topic of interest over the past few years as stakeholders look for more economical and technically feasible options for treating groundwater impacted by these compounds (McGregor, 2018;McGregor and Maziarz, 2021;McGregor and Zhao, 2021;McGregor and Carey, 2019). The emerging compounds of concern that have garnered the most attention is the PFAS with most studies focused on the aboveground treatment.…”

Section: Introductionmentioning

confidence: 99%

“…Simon (2020) estimated that there may be greater than 42,000 PFAS-impacted sites around the world which could cost over $80 billion to address. The in-situ treatment of PFAS is limited to a few field studies (Darlington et al, 2018;Interstate Technology and Regulatory Council ITRC, 2018;McGregor, 2018;Ross et al, 2018;McGregor, 2020a;McGregor and Zhao, 2021). The treatment of PFAS-impacted groundwater is complex due to numerous physical and chemical factors.…”

Section: Introductionmentioning

confidence: 99%

“…Laboratory and field studies for the in-situ treatment of dissolved PFAS have focused on using sorptive media for the removal of the PFAS with chemical oxidation also being evaluated. (Higgins and Luthy, 2006;Park et al, 2016;Bruton and Sedlak., 2017;Eberle et al, 2017;Dombrowski et al, 2018;McGregor, 2018;Aly et al, 2019;Barajas, 2019;Carey and McGregor, 2019;McGregor, 2020a;Interstate Technology and Regulatory Council ITRC, 2020;Liu et al, 2020;McGregor and Zhao, 2021). Sorptive media for the in-situ treatment of dissolved PFAS is limited by the amount of sorptive capacity of the media itself (Higgins and Luthy, 2006;Yu et al, 2009;Carter and Farrell, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…McGregor (2020aMcGregor ( , 2018 showed that CAC is effective at removing both PFAS and other organic compounds of concern including benzene (B), toluene (T), ethylbenzene (E), xylene (X), gasoline, and diesel range petroleum hydrocarbons (GRO and DRO). McGregor and Zhao (2021) demonstrated at a site with trichloroethene (TCE) and its dichlorination by-products; 1.2 cis dichloroethene (1,2 DCE), and vinyl chloride could be treated to regulatory requirements within a moderately heterogenetic aquifer system. Numerical modeling of field data by Carey and McGregor (2019) estimated that CAC would be effective at controlling back/matrix diffusion reactions over several decades.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Heterogeneity on the Distribution and Treatment of PFAS in a Complex Geologic Environment

McGregor¹,

Benevenuto²

2021

Front. Environ. Chem.

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Per-and polyfluoroalkyl substances (PFAS) have been identified as emerging contaminants of concern in the environment in a wide variety of media including groundwater. Typically, PFAS-impacted groundwater is extracted by pump and treat systems and treated using sorptive media such as activated carbon and ion exchange resin. Pump and treat systems are generally considered ineffective for the remediation of dissolved phase contaminants including PFAS but instead are considered applicable for plume containment. An alternative to pump and treat is in-situ treatment. The demonstrated use of in-situ treatment for PFAS-impacted groundwater is limited with only colloidal activated carbon (CAC) being shown to effectively attenuate PFAS over short and moderate time periods. Active research topics for the in-situ treatment of PFAS include the effect of heterogeneity on the distribution of the CAC, the lifespan of the CAC itself, the effect of competitive adsorption/absorption, and the effect of other geochemical conditions on the removal process. This study looked at the effect of heterogeneity on the distribution of CAC and subsequent treatment of PFAS at a site with a multiple aquifer system. The site’s geology varied from a silty sand to sand to fractured bedrock with all three units being impacted by PFAS and benzene (B), toluene (T), ethylbenzene (E), and xylene (X). Parameters evaluated included the distribution of the CAC as well as the subsequent treatment of the PFAS and BTEX. Results of groundwater sampling indicated that the PFAS detected within the groundwater were treated effectively to below their respective reporting limits for the duration of the 1-year test in both the silty sand and sand aquifers. The PFAS in the fractured rock aquifer showed a different treatment profile with longer carbon chained PFAS being attenuated preferentially compared to the shorter carbon chained PFAS. These results suggest that competitive sorptive reactions were occurring on the CAC within the fractured rock. Analysis of the unconsolidated aquifer materials determined that direct push injection of the CAC was effective at delivering the CAC to the target injection zones with post-injection total organic carbon (TOC) concentrations increasing by up to three orders of magnitude compared to pre-injection TOC concentrations. Heterogeneity did have an impact on the CAC distribution with higher hydraulic conductivity zones receiving more CAC mass than lower hydraulic conductivity zones.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Effect of Heterogeneity on the Distribution and Treatment of PFAS in a Complex Geologic Environment

McGregor¹,

Benevenuto²

2021

Front. Environ. Chem.

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“…In situ application of CAC has been successfully used to attenuate chemicals such as petroleum hydrocarbons, per‐ and polyfluoroalkyl substances, synthetic musks, and chlorinated volatile organic compounds, (McGregor & Carey, 2019; McGregor, 2018; Nardo et al, 2010; Simon, 2015). Due to its small particle size (~1–2 microns), CAC can be injected into the subsurface at lower pressures than other forms of activated carbon, resulting in a more uniform distribution of the CAC (McGregor, 2018; McGregor & Zhao, 2021). Compared to granular/powdered forms of activated carbon, CAC has a greater surface area which promotes more adsorption sites and a longer activated carbon lifespan.…”

Section: Introductionmentioning

confidence: 99%

The in situ treatment of Basic Violet 16 synthetic dye in groundwater

McGregor¹,

Maziarz

2021

Remediation Journal

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Synthetic dyes have been shown to be micropollutants in various aquatic and groundwater systems, often occurring at milligram per liter (mg/L) concentrations. Synthetic dyes are typically introduced into the environment either as a continuous stream from wastewater or as episodic events related to the disposal of residues or spills generated during the manufacturing process. Various studies for the treatment of synthetic dyes have been undertaken for wastewater but studies for the in situ treatment of synthetic dyes in groundwater are limited. A pilot‐scale test was conducted to determine if the use of colloidal activated carbon (CAC) could effectively reduce dissolved concentrations of the synthetic dye Basic Violet (BV16) in groundwater using in situ methods. The pilot test was carried out downgradient of a textile manufacturing facility where historic disposal practices resulted in the release of various chemicals of concern including BV16 to an unconfined silty sand aquifer. A 10‐weight percent CAC solution was injected into a series of temporary direct push injection points to target the synthetic dye that was present at concentrations of up to 1,640 micrograms per liter (μg/L) during the 738‐day study. The results from the pilot test indicated that the CAC was effectively delivered to the target injection zone resulting in a three order of magnitude increase in total organic carbon (TOC) concentrations compared to preinjection TOC concentrations within the aquifer. Distribution of the CAC within the targeted injection zone indicated that heterogeneity affected the distribution with a zone of higher horizontal hydraulic conductivity (KH) having an average TOC concentration approximately 100 percent greater than the mean TOC concentration within the surrounding aquifer targeted by the CAC injection. Analyses of the groundwater chemistry before and postinjection indicated that the CAC had no detrimental impact on the groundwater quality while reducing the concentration of dissolved BV16 within the plume to below the method detection limits within 62 days of injection. The concentration of BV16 remained below the method detection limit of 10 µg/L for the 738‐day duration of the study apart from one detection of 180 µg/L at Day 183 within groundwater sampled from one monitoring well suggesting that the CAC was effective in attenuating the BV16 over the short and moderate term.

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PFAS Experts Symposium 2: Statements on available in situ remediation technologies

Abrams¹,

McGregor²,

Burns³

et al. 2022

Remediation Journal

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As a follow-up to the PFAS Experts Symposium 2 held on June 30 and July 1, 2021, the In situ Remediation Technologies Committee prepared a technical and regulatory review of in situ technologies that are potentially applicable to sites with per-and polyfluoroalkyl substances (PFAS) contamination. The technologies included in the review were limited to those that are deemed commercially available and potentially applicable to sites with soil, groundwater, surface water, and sediment contamination. While the scope of commercially available in situ remediation technologies for PFAS remains limited, some in situ adsorption technologies, most notably activated carbon-based technologies, can be considered fully commercialized. Though questions remain regarding the long-term effectiveness of these technologies, field applications deployed for at least a half-decade or more continue to demonstrate effectiveness. | INTRODUCTIONThis paper was developed from presentations given at the PFAS Experts Symposium 2 (Symposium), a virtual, invitation-only conference held on June 30 and July 1, 2021. A previous PFAS Experts Symposium was held in May 2019. A primary objective of the Symposium was to share current information on per-and polyfluoroalkyl substances (PFAS) among experts in different scientific and technical fields. All listed authors participated in the Symposium and contributed to the discussions and presentations on available in situ remediation technologies to treat PFAS contamination in various environmental media.The Committee on "Available In Situ Remediation Technologies" was charged with benchmarking a key subset of remediation technologies. The concept of "in situ" technologies is widely understood to include technologies that provide treatment or containment within the subsurface. Further, "available" was defined by the Committee as technologies that have advanced beyond the research stage and are available for use either now or in the near future.

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The in situ treatment of TCE and PFAS in groundwater within a silty sand aquifer

Cited by 16 publications

References 20 publications

The Effect of Heterogeneity on the Distribution and Treatment of PFAS in a Complex Geologic Environment

The Effect of Heterogeneity on the Distribution and Treatment of PFAS in a Complex Geologic Environment

The in situ treatment of Basic Violet 16 synthetic dye in groundwater

PFAS Experts Symposium 2: Statements on available in situ remediation technologies

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