The two components „PFAS Adaptive Mobilisation“ und „Electric Force Sorption“ are part of the modular system to extract PFAS from the environment (PFClean): i) the „adaptive mobilisation“ part, where long-chain, immobile (precursor) substances are mobilized into shorter-chain, more mobile substances with the help of a groundwater circulation well (GCW); and ii) a „funnel & gate system in which PFAS are being adsorbed. The adsorption is improved with electric polarisation.
PFAS are a large group of persistent, ubiquitous, and partly toxic substances („chemicals of emerging concern“). The two systems „PFAS Adaptive Mobilisation“ and „Electric Force Sorption“ enable the extraction of PFAS from the subsurface environment.
With the help of a GCW the environmental conditions in the aquifer were adapted such that microbially mediated transformation processes are enhanced. These processes transform longer-chain and immobile (precursor) substances into shorter-chain and mobile substances. This was achieved by adding heat and oxygen in the GCW and mixing them in the aquifer.
The sheet piles of the „funnel“ guide the groundwater flow towards the „gate“. In the gate, there is sorbent material (activated carbon) to which PFAS adsorb and subsequently can be extracted from the environment. So far activated carbon was known to be not efficient for retaining short-chain PFAS. By applying an electrical voltage, this disadvantage was eliminated. When the polarity is reversed, a highly concentrated eluate is being released that is well suited for subsequent treatment.
The system was realized close to ground surface in an urban, closely built environment. The space requirements were small, all of which is a typical challenge at contaminated sites. Additionally, the sorbent material in the gate can easily be exchanged. The pilot site in Reilingen is the first site, where both systems were successfully used, according to our knowledge. The PFAS concentrations in groundwater, as well as temperatures and oxygen levels were monitored in detail.
