• • Synergistic addition of 6 mmol·L−1 lactate and microbial immobilization increased maximum power density to 22.06 mW·m−2, a 194% improvement over the blank, and raised maximum output voltage to 88.75 mV (2.09× non-immobilized), demonstrating effective enhancement of SMFC electrochemical performance.
• • At the optimal lactate concentration (6 mmol·L−1), TOC and TN removal rates reached 29.02% and 28.4%, respectively, outperforming the control (22.41% and 21.42%), while high lactate concentrations caused TOC accumulation due to metabolic inhibition, indicating a critical threshold for carbon source dosing.
• • 16S rRNA analysis identified Bacillota and Pseudomonadota as the dominant phyla on the anode, both possessing electroactive and pollutant-degrading functions, confirming that lactate enriches functional bacteria and immobilization prevents their loss, thereby stabilizing the microbial community.
• • The combined strategy of lactate regulation and immobilization addresses the bottlenecks of low electron transfer efficiency and unstable microbial communities in traditional SMFCs, offering a scalable approach for in-situ remediation of eutrophic and industrially polluted sediments with simultaneous energy recovery.