Integrating Adsorption and Enhancing Feammox Reaction: Activated Carbon and Ion Exchange Resins as Microbial Carriers for Wetland Enrichment Culture

Abstract

Per- and polyfluoroalkyl substances (PFAS) resist conventional degradation because of the thermodynamic stability of their carbon-fluorine bond, and current treatment relies on granular activated carbon (AC) and ion exchange resins (IER) that only sequester rather than degrade the contaminant, thus generating PFAS-laden waste that requires disposal as hazardous waste or energy-intensive thermal regeneration above 800 °C. This thesis investigates an integrated paradigm in which AC and IER serve simultaneously as PFAS sorbents and as microbial carriers for Acidimicrobium sp. strain A6 (A6), the first organism shown to defluorinate perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) through the anaerobic ammonium oxidation coupled to ferric iron reduction (Feammox) pathway. The hypothesis is that these solid sorbents can both concentrate PFOA at the solid-liquid interface while sustaining A6 metabolism, co-locating adsorption and biological transformation within one engineered unit. Four materials, SIR-110-MP-HP, SIR-110-HP, ASM110 iron hybrid resin, and AGC-PFx coconut shell activated carbon, were evaluated across five phases. Phase #1 quantified abiotic PFOA sorption; phase #2 ran a 310-day anaerobic incubation under four conditions to assess Feammox activity, fluoride production, and PFOA partitioning; phase #3 compares post-incubation adsorption capacity of A6-treated and fresh sorbents to test biological regeneration; phase #4 will characterize fluoride sorption in Tris buffer to generate buffer-specific correction factors; and phase #5 will extend the system to Pseudomonas strains. All sorbents adsorbed greater than 98% of PFOA abiotically. Sustained ammonium reduction in treatments with A6 showed active Feammox over 310 days, with AGC supporting the strongest sorbent-bound microbial performance up to 19.8%. Fluoride production in experimental conditions exceeded abiotic controls and represented 5-15% of the theoretical maximum from complete defluorination. Methanol extraction recovered measurable PFOA exclusively from A6-treated sorbents, indicating microbially mediated modification of PFAS–sorbent binding. As a whole, results indicated that AC and IER are viable Feammox carriers whose biological activity alters PFOA at the sorbent surface, supporting integrated adsorption–biodegradation platforms that will help to reduce reliance on thermal regeneration and advance toward partial PFAS destruction within engineered systems.