Challenges and Current Status of the Biological Treatment of PFAS-Contaminated Soils

Abstract

Per- and polyfluoroalkyl substances (PFAS) are Synthetic Organic Compounds (SOCs) which are of current concern as they are linked to a myriad of adverse health effects in mammals. They can be found in drinking water, rivers, groundwater, wastewater, household dust, and soils. In this review, the current challenge and status of bioremediation of PFAs in soils was examined. While several technologies to remove PFAS from soil have been developed, including adsorption, filtration, thermal treatment, chemical oxidation/reduction and soil washing, these methods are expensive, impractical for in situ treatment, use high pressures and temperatures, with most resulting in toxic waste. Biodegradation has the potential to form the basis of a cost-effective, large scale in situ remediation strategy for PFAS removal from soils. Both fungal and bacterial strains have been isolated that are capable of degrading PFAS; however, to date, information regarding the mechanisms of degradation of PFAS is limited. Through the application of new technologies in microbial ecology, such as stable isotope probing, metagenomics, transcriptomics, and metabolomics there is the potential to examine and identify the biodegradation of PFAS, a process which will underpin the development of any robust PFAS bioremediation technology.

PFAS Molecules: A Major Concern for the Human Health and the Environment

“…Recent reports estimate that the number of potential sites hosting installations emitting in some quantity PFAS, is in the order of 100,000 or more in the sole EU, a number which might further increase in the next future [70]. Based on these considerations, it is not surprising that PFAS have become pervasive environmental pollutants impacting on the ecosystems and human health through the contamination of multiple routes of human exposure via the environment including the atmosphere, the drinking water, the cereals, fruits, vegetables, milk and other food sources [71][72][73][74][75].…”

“…In line of principle, both on-site and off-site methods can be used to immobilize, transform or destroy PFAS in the environmental matrix of interest, but their huge variability, the increasing number of alternatives and considerations related to costs effectiveness and environmental impact, have narrowed the number of effective treatments to a bunch of PFAS (i.e., PFOS and PFOA) for which the environmental fate, transformation pathways and physicochemical properties are well known [8]. Given the importance of water sources for human health, the vast majority of the efforts have historically focused on the development of effective methods to sequester or remove PFAS substances from contaminated liquid streams such as groundwater, drinking water, wastewater and other industrial effluents while only later the interest has moved towards the implementation of valid strategies for soil remediation [71,259]. Here below, some of the most common remediation techniques for PFAS remediation will be briefly presented while the reader interested to a more detailed description is referred to other excellent reviews [8,73].…”

“…The amphipathic properties of PFAS substances are largely responsible of PFAS adsorption to soil particles and sediments, a process which is influenced by the environmental pH, soil geochemical composition, the total organic carbon content (mainly humic and fulvic acids), the presence of proteins or saccharides as well as the content of iron and aluminum oxides [71]. Several remediation techniques have been developed and tested to immobilize, remove or destroy PFAS substances in the soil while others are still under investigation and full implementation from the laboratory to the field scale size.…”

“…More recently, two strains of Pseudomonas (PS27 and PDMF10) isolated from PFAS-contaminated sites were found to bioaccumulate (but not degrade) and thus to remove 32% and 28% of PFHxS contamination within 10 days, respectively [302]. An alternative bioremediation strategy is represented by the use of plants that bioaccumulate PFAS substances in their root or leaves leading to the removal of these contaminants from the soil without inducing their degradation [71]. In a former report from Gobelius et al, analyzed the uptake of 26 PFAS in different plant species grown on the soil near to a fire training site at Stockholm Arlanda airport, contaminated with levels of total PFAS ranging from 16 to 160 ng/g dw.…”

Per- and Polyfluoroalkyl Substances (PFAS) in Integrated Crop–Livestock Systems: Environmental Exposure and Human Health Risks

“…PFOA, PFOS, PFBA, PFHxS and other PFAS Reservoir for products containing PFAS chemicals that undergo decomposition, disposal of waste during primary and secondary manufacturing process using PFAS[15,18,19] Printing/paper product production PFOA, PFOS, PFBA and other PFAS Surface coatings to repel grease and moisture[13,20] Wastewater treatment PFOA, PFOS, PFBA and Application of treated wastewater especially in agricultural lands water from manufacturing, industrial and household[15,17,[21][22][23][24] …”