EGU2020-17615, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-17615
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Pilot-scale injection of colloidal activated carbon for PFAS immobilization at a contaminated field site

Fritjof Fagerlund1, Georgios Niarchos1, Lutz Ahrens2, Dan Berggren Kleja3, Jonny Bergman4, Anna Larsson4, Gareth Leonard5, Jim Forde5, Johan Edvinsson6, Katrin Holmström6, Henning Persson7, and Lijana Gottby7
Fritjof Fagerlund et al.
  • 1Uppsala University, Earth Sciences, Uppsala, Sweden (fritjof.fagerlund@geo.uu.se)
  • 2Swedish Agricultural University, Aquatic Sci. & Assessment, Uppsala, Sweden
  • 3Swedish Agricultural University, Soil & Environment, Uppsala, Sweden
  • 4RGS Nordic, Sweden
  • 5Regenesis, UK
  • 6NIRAS, Sweden
  • 7Swedish Geological Survey, Uppsala, Sweden

Per- and polyfluorinated alkyl substances (PFASs) are extremely recalcitrant contaminants that pose a challenge for remediation in soil and groundwater due to their chemical stability and resistance to degradation. They are used in numerous consumer products and their use in firefighting aqueous-film-forming foams has led to worldwide contamination of groundwater resources associated with airports and firefighting training areas. One of the currently most promising in-situ treatment techniques is stabilization using activated carbon (AC) sorbents that can immobilize PFASs in the soil and prevent further spreading from a contaminated site. However, few documented field studies exist.

In this study we investigated in-situ stabilization of PFASs by injection of colloidal activated carbon (CAC, PlumeStop®) at a PFAS contaminated site in Arboga, Sweden. Prior to the design of the pilot-scale test and CAC injection, the geology and state of contamination were carefully characterized and PFAS concentrations and groundwater levels were monitored continuously for almost one year. CAC was injected to create a defined zone of PFAS-sorption where PFASs from the contaminant plume would be sorbed to CAC and removed from the flowing groundwater, similar to a permeable reactive barrier. The effect of the injected CAC was studied by monitoring PFAS concentrations in the groundwater up- and down-gradient as well as within the CAC barrier both before and after injection. General water chemistry and groundwater levels were also monitored.

The site characterization showed that there are two distinct source zones of PFAS contamination with different contamination signatures. Continuous baseline monitoring prior to CAC injection did not show any major changes in PFAS concentrations, but revealed seasonal variations in the groundwater levels and flow patterns, leading to seasonal changes also in the direction of contaminant transport. The CAC injection pilot-scale test was therefore designed to shield the down-gradient evaluation wells in small part of the plume accounting for seasonal changes. The geological setting of the site mainly is clayey till soil of relatively low hydraulic conductivity on top of crystalline bedrock, but there are also high permeability flow paths. The low-pressure CAC injections were hence designed and adapted to avoid excessive preferential flow of CAC and achieve a good distribution of CAC in the intended treatment zone (barrier).

Preliminary results from the monitoring showed strong reduction of all measured PFASs within and directly down-gradient of the CAC barrier. These results indicate that the installation of the CAC barrier was successful despite a relatively complex geological setting where fast preferential flow paths exist. The continuing monitoring will show how the CAC performs over time.

How to cite: Fagerlund, F., Niarchos, G., Ahrens, L., Berggren Kleja, D., Bergman, J., Larsson, A., Leonard, G., Forde, J., Edvinsson, J., Holmström, K., Persson, H., and Gottby, L.: Pilot-scale injection of colloidal activated carbon for PFAS immobilization at a contaminated field site, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17615, https://doi.org/10.5194/egusphere-egu2020-17615, 2020

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