Transport and Transformation of Poly- and Perfluoroalkyl Substances (PFAS) in Constructed Wetland Mesocosms as Coupled to the Feammox Process

Per- and polyfluoroalkyl substances or PFAS are emerging contaminants that are known for their stability due to their strong carbon-fluorine bond. This bond has resulted in their use in a multitude of industrial and household products such as non-stick cookware and firefighting foam, however, recent studies have linked PFAS to cancer in humans and has led to the EPA's PFAS Strategic Roadmap.

With the recent discovery of the bacterium Acidimicrobium sp. Strain A6 in wetlands and subsequent research into their ability to couple the Feammox process with PFAS defluorination, wetlands have become an important PFAS remediation method. In this study, several constructed wetland mesocosms were used to study PFOA transport and biodegradation in the presence of Scirpus acutus plants (bulrush). Pure sand was coated with 2-line ferrihydrite before being packed into each column (36cm x 15cm) and inoculated with the A6 culture. After the A6 culture was established and the plants fully grown, a mixture of PFAS and ammonium was introduced from the bottom of the columns at a constant rate for 90 days. Samples were taken periodically in the effluents at the top and inside of the soil column via the effluent port and five sampling ports at 6 cm intervals and analyzed for PFOA and intermediate degradation products.

A subsequent fate and transport model was developed to couple the Feammox process with PFAS biodegradation. Sensitivity analysis showed that the model was able to simulate A6 activity and correctly responded to plant PFAS uptake, PFAS sorption, flow rate, and plant transpiration. Analysis of the mesocosm samples is currently undergoing and will be used for model evaluation.