Denitrification reaction performance in three-dimensional biofilm electrode reactors using self-releasing carbon biofilm electrodes

Agricultural waste, corncobs, and sponge iron were used to develop a self-releasing carbon biofilm electrode (SRC-BE) and utilized for denitrification experiments in three-dimensional biofilm electrode reactors (3D-BERs). Fe2+ was released to enhance the extracellular electron transfer. Following an alkali treatment, SRC-BE were introduced into 3D-BERs of the electrode group (EG), with iron serving as the anode-cathode plate in the EG. Under a current density of 0.1 mA/cm2, hydraulic retention time of 2 h, and dissolved oxygen control at 0.5–1.0 mg/L, the removal rates were as follows: the highest removal rates were 71.09 % for total nitrogen, 40.26 % for NH4+-N, and 84.34 % for NO3−-N, with a stable 96.87 % removal rate for total phosphate. The effluent chemical oxygen demand in the EG remained stable at approximately 12 mg/L during the stable phase, thus reducing the risk of secondary pollution. The enrichment of electroactive microorganisms and functional genes related to C and N also verified their denitrification efficacy.