Comparative assessment of coke and petroleum coke as potential electrode materials in constructed wetlands-microbial fuel cells

Incorporating conductive filling materials into electrode layers can enhance the performance of constructed wetland-microbial fuel cells (CW-MFCs). This study employed petroleum coke and coke to separately construct two CW-MFCs (i.e., PC-CW-MFC and C-CW-MFC). Both systems achieved optimum performance when subjected to aeration at 0.4 L/min, 300 mg/L chemical oxygen demand loading, and three-day hydraulic retention. Due to the coke's porous structure, C-CW-MFC outperformed PC-CW-MFC with the chemical oxygen demand removal efficiency, total nitrogen, and PO 4 3– P up to 96.23 %, 89.63 %, and 65.68 %, respectively. Besides, the maximum output voltage was 874.5 mV. This superiority was attributed to the notable diversity of denitrifying bacterial community, along with the relatively high abundance of nirS and nirK copies. Gas chromatography-mass spectrometry showed that petroleum coke and coke did not cause secondary environmental pollution of polycyclic aromatic hydrocarbons. These outcomes indicate that introducing coke in CW-MFCs represents a potential competitive technology to enhance wastewater treatment and energy recovery. • Two CW-MFCs using coke and petroleum coke as electrode materials were constructed • Optimization was explored based on different operating parameters. • C-CW-MFC showed a better performance than PC-CW-MFC. • Coke was beneficial for denitrifying bacterial diversity and function. • Coke enriched JG30-KF-CM45 to remove PO 4 3– P.