Tailoring microbial redox with alternating current for efficient mineralization of refractory organic nitrogen compounds in wastewater

Traditional biological wastewater treatment struggles to efficiently remove refractory organic nitrogen compounds (RONCs). This study demonstrates the potential of alternating current (AC)-driven bioelectrodes for deep mineralization of nitrobenzene (NB) by coupling in situ reduction and oxidation reactions. Sine-wave AC bioelectrodes overcome the limitations of direct current (DC) systems, achieving 97.6% NB reduction, 90.9% intermediate mineralization, and 80.8% total nitrogen removal while reducing energy consumption by 22.3%. AC stimulation enhances biofilm formation and bidirectional electrocatalytic activity, leading to higher biomass and electron utilization efficiency. Multi-omics analysis shows enrichment of functional microbial consortia involved in NB reduction, aromatic compound oxidation, ammonia oxidation, nitrate/nitrite reduction, and electron transfer, with upregulated enzyme gene expression. Carbon metabolites from catechol meta-cleavage support nitro-reduction, denitrification, and cell viability without external carbon sources. Nitrification-denitrification is the primary pathway for inorganic nitrogen removal. This AC bioelectrode offers an efficient, low-carbon solution for RONC mineralization in wastewater.