The emergence of newly-identified contaminants of concern, such as 1,4-dioxane and per- and polyfluoroalkyl substances (PFAS), has resulted in changing regulatory criteria, as agencies obtain more information about their chemical properties.
PFAS remediation is extremely challenging, as it is difficult to biodegrade, oxidize, reduce or volatize. That said, using the FlexHeater™ technology, TRS can heat the treatment volume to about 400° Celsius. TRS has demonstrated the removal of 99.997% of PFAS from soils, regardless of the total organic carbon levels. TRS then collects the gas phase compounds and scrubs them for subsequent treatment. As the maximum temperature of water is its boiling point, TRS envisions applying the FlexHeater™ technology for PFAS treatment primarily in the vadose zone.
Cornelsen, a TRS Europe in situ thermal remediation partner based in Germany, has developed a PFAS-impacted groundwater pre-treatment
system that involves mixing the aqueous phase PFAS with PerfluorAd, which removes by filtration a high percentage of the PFAS. Thus,
PerfluorAd is quite cost effective, as it will extend the life of granular activated carbon to treat the remaining aqueous phase PFAS.
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The high solubility and low Henry's Law constant of 1,4-dioxane combine to present complex challenges with respect to its remediation. TRS has applied ERH and demonstrated 1,4-dioxane removal in the laboratory and in the field. At ambient conditions, the physical properties of 1,4-dioxane indicate air stripping is not an efficient treatment mechanism; however, a major treatment process for ERH involves steam stripping, which has reasonable efficiency at elevated temperatures.
TRS conducted laboratory testing to identify the properties that influence remediation of 1,4-dioxane using ERH. We found that TRS ERH steam stripping method effectively transferred 1,4-dioxane to the vapor phase for subsequent treatment. During field implementation of ERH, TRS achieved greater than 99.8 percent reductions in 1,4-dioxane groundwater concentrations. Process stream monitoring in the field indicated 95 percent of 1,4-dioxane remained in the vapor stream after removal from the subsurface. Furthermore, granular activated carbon has proved to be an effective 1,4-dioxane vapor treatment method.
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