Alternating Current-Driven Bioredox Cycling Achieves in Situ Deep Mineralization of Nitroaromatic Pollutants in Sediments

Nitroaromatic compound (NAC)-contaminated sediments pose threats to aquatic ecosystems. The challenges of low mass transfer in sediments and the recalcitrance of NACs to degradation limit the effectiveness of conventional bioremediation techniques. This study demonstrates the potential of alternating current (AC)-driven bioredox cycling to overcome these barriers by coupling in situ reduction-oxidation processes. We report the successful application of AC stimulation in achieving the mineralization of nitrobenzene (NB) while elucidating its role in modulating bioredox dynamics, electron transfer, and electromicrobiome function. Sine-wave AC stimulation achieved an 87.7% reduction of NB and 90.3% mineralization of its intermediates. The AC stimulation promoted robust biofilm formation, enhanced bidirectional electrocatalytic activity, and increased microbial biomass. It also enriched a diverse microbial consortium capable of reducing NB, oxidizing aromatic intermediates, and facilitating electron transfer, as indicated by the upregulation of key enzymatic genes through multiomics analyses. Carbon metabolites from catechol meta-cleavage further supported nitro-reduction and sustained microbial viability. Compared to DC processes, AC-driven bioredox cycling reduced energy consumption by 16.8% in the remediation of NB-contaminated sediments. This approach offers a sustainable, low-carbon solution for efficient in situ biomineralization of NACs in sediments.