Bioelectrochemical stimulation enhances phosphine production and phosphorus removal from carbon–limited wastewater during anaerobic digestion

Biological phosphorus removal from carbon–limited municipal wastewater remains a significant challenge due to insufficient electron donors and competing reduction processes. This study developed an anaerobic–bioelectrochemical system (BES) incorporating a granular activated carbon (GAC) biocathode to enhance biological phosphorus removal via phosphine (PH 3 ) production. Over a 7-day batch operation, the total phosphorus (TP) in the BES + GAC reactor decreased to 6.9 mg L −1 , corresponding to a TP removal efficiency of 48.1%, compared with 25.5% in the control. Meanwhile, the average PH 3 concentration in the biogas reached 24 μg m −3 during days 2–7, which was 1.77 times higher than that of the control. Microcurrent stimulation maintained a strongly reducing environment (oxidation–reduction potential < −460 mV) and enriched phosphorus transport-related genes, while enhancing alkaline phosphatase and dehydrogenase activities. The applied microcurrent also promoted cell lysis, releasing intracellular organic matter that was subsequently converted into short-chain fatty acids; the resulting shift in carbon utilization was accompanied by lower methanogenesis and sulfate reduction, while phosphate and nitrate reduction were enhanced. Microbial community analysis further showed enrichment of Candidatus Competibacter and denitrifying phosphorus-accumulating organisms, enabling simultaneous nitrogen and phosphorus removal. These findings elucidate the synergistic effects of electrode material, microcurrent, and microbial dynamics on anaerobic phosphorus transformation, and offer a mechanistic basis for enhancing biological phosphorus removal from carbon–limited wastewater.