rGO/polypyrrole-modified bioelectrode reshapes microbial communities for enhanced energy-recovering denitrification...

A denitrifying bio-electrochemical system (BES) with reduced graphene oxide/polypyrrole (rGO/PPy)-modified biocathodes was explored to achieve near-complete nitrate removal at low carbon-to-nitrogen (C/N) ratios (1, 3, and 5). Mechanistic investigations indicated that the rGO/PPy scaffold provided high surface area microbial anchoring sites and mediated efficient electron shuttling between the electrode and biofilm. The conductive 3D rGO/PPy network facilitated direct extracellular electron transfer, eliminating the need for organic carbon supplementation while achieving a maximum power density of 8.2 ± 0.9 mW/m² with a coulombic efficiency of 59.1 % at C/N of 5. 16S rRNA sequencing revealed a uniquely balanced consortium dominated by Geobacter (electrogenic), Comamonadaceae (heterotrophic denitrifier), and Thauera (autotrophic denitrifier). Co-occurrence network analysis further demonstrated cross-feeding interactions between these functional groups, enabling concurrent heterotrophic and electrodic autotrophic denitrification pathways. This abiotic-biotic synergy establishes an energy-positive wastewater treatment paradigm, achieving carbon-neutral nitrogen removal with reduced operational costs.