Enhanced fluoroglucocorticoid removal from groundwater in a bio-electrochemical system with polyaniline-loaded activated carbon three-dimensional electrodes: Performance and mechanisms.

This study aimed to investigate the removal performance and mechanisms of dexamethasone (DEX), a representative fluoroglucocorticoid (FGC), from micro-polluted oligotrophic groundwater in a bio-electrochemical system amended with polyaniline-loaded activated carbon (PANI@AC) as three-dimensional particle electrodes (BES-3D). The BES-3D achieved a DEX removal efficiency of 95.7%, which was 39.0% and 14.1% higher than that of a single biological system (SBIO) and two-dimensional bio-electrochemical system (BES-2D), respectively. The preliminary metabolic mechanism of defluorination accounted for 53.5%, 41.1%, and 16.3% in BES-3D, BES-2D, and SBIO, respectively, which was accompanied by demethylation, side-chain fracture, and hydroxyl oxidation for ketone formation and final-ring opening. The main mechanism by which removal was improved in BES-3D was the enrichment of functional microbes and enhancement of the expression of dehalogenation genes. The relative abundance of functional microbes with electron transfer ability and reductive dehalogenating genera, i.e., Pseudomonas , Methylotenera, Desulfuromonas, Sphingomonas, and Microbacterium , in BES-3D was 3.7–6.1 times higher and the copy number of functional genes was 1.9 times higher than those of SBIO, which contributed to the high DEX removal. [Display omitted] • DEX removal efficiency from groundwater reached 95.7% in BES-3D. • PANI@AC amendment enhanced reductive defluorination and electron transfer. • Primary metabolic pathways included defluorination and side-chain rupture. • Defluorination accounted for 53.5% of metabolic removal in BES-3D. • Functional microbes with reductive dehalogenation contributed to DEX removal. [ABSTRACT FROM AUTHOR]