Optimizing soil washing for PFAS contaminated soil - Flocculation and coagulation
Creators: name: Michel, Hubert
name: Hansen C. Mona
name: Sarah, Hale E.
name: Meyn Thomas
name: Varela C. Gabriela
name: Asimakopoulos G. Alexandros
name: Henriksen, Thomas
name: Arp H. Hans Peter
Publisher: name: Zenodo
Year: 2023
Subjects: PFAS, remediation, soil washing, coagulation, flocculation

description: <strong>Presentation at Nordrocs 2022 - crossing borders conference, Oslo (September 2022)</strong> Abstract: Poly- and perfluorinated alkyl substances (PFAS) are a group of widely used, man-made chemicals showing resistance to chemical, biological/physical degradation processes and high potential for bioaccumulation and toxicity to organisms (Buck et al. 2011). A recent estimate of the number of potentially contaminated PFAS sites in Europe was 100 000, including several fire-fighting training facilities at airports or military bases (Nordic Council of Ministers 2019). With such an abundance of PFAS impacted sites, there is an urgent need for diverse and innovative technologies to effectively treat PFAS in contaminated media. Soil washing as an ex-situ technology able to remove contaminants from soil and has been proven to be effective for different soil contaminants including PCBs, PCPs, heavy metals. (US EPA, 1993). To date, there are few soil-washing facilities worldwide processing PFAS contaminated soils. To support the use of soil washing as a remediation technique, this research focuses on the optimization and development of guidelines for soil-washing of PFAS contaminated soil and the reuse of the resulting processed material. Deriving Kd-values for different soil size fractions representative of the materials produced at different stages in a typical washing process is one objective of this work. In order to increase environmental sustainability and economic feasibility of the soil washing process, the water used should be cleaned and then reused in the process. Due to the overall large surface area of the grains and possible high content of organic matter on finer particles, the separation of colloidal soil particles from the washing water is important. One way to treat wash water is by coagulation and flocculation of colloids followed by sedimentation of the aggregated particles. Currently, the removal efficiency of different coagulants and flocculants for PFAS contaminated soils has not been investigated. Flocculation tests (jar-tests) has been carried out to compare the removal efficiency of different flocculants tested on the finer particles. The findings of this research will help to develop a 1D-box-model to evaluate and model soil washing processes for different PFAS contaminated materials. Soil washing is a well-known ex-situ technique for cleaning contaminated soil, however this work presents steps forward for the use of this technique for PFAS contaminated soils. Performing batch- and flocculation tests and developing modelling approaches will help to develop guidelines for an efficient washing process to enhance the regulatory acceptance of this remediation technique. <strong>References:</strong> Buck, et al., Perfluoroalkyl and Poly-Perfluoroalkyl and Polyfluoroalkyl Substances in the Environment: Terminology, Classification, and Origins. Integrated Environmental Assessment and Management, 2011, 7(4):513-41. Nordic Council of Ministers, The cost of inaction – A socioeconomic analysis of environmental and health impacts linked to exposure to PFAS, 2019, TemaNord No. 516. US EPA, Innovative Site remediation Technology: Soil Washing/Soil Flushing, 1993, EPA 542-B-93-012.