Hybrid bioelectrochemical process enables hierarchical C, N, and P utilization towards negative carbon emission wastewater treatment.

Bioelectrochemical system (BES) can provide sustainable solutions for wastewater treatment through lower energy consumption, reduced carbon emissions, and nutrient capture and reuse. Herein, we propose a hybrid bioelectrochemical assembly (HBA)-centered purification-power-cultivation process to achieve hierarchical C, N, and P metabolism, graded power generation, and reusable water production. The hybridization of abiotic and biotic cathode BESs in HBA enables hierarchical C metabolism, with effluent COD directly meeting the Class Ⅲ surface water standard. The customized water-permeable biofilm separators sequentially create anaerobic-anoxic-aerobic zones within HBA, enabling complete N removal. Subsequently, the P-rich tailwater of HBA is channelled into a hydroponic irrigation system for P utilization, ultimately producing reusable clean water. Notably, a high power density of 0.43 W m-2 is obtained, and this process achieves a net carbon emission of -0.413 kg-CO2 m-3. This study presents a prototype for sustainable wastewater purification, particularly in low-resource areas with carbon emission reduction and carbon neutrality targets.