Sulfate-reducing bacteria treating sulfate-containing wastewater based on improving electron transfer efficiency: A...

Sulfate-reducing bacteria (SRB) play a critical role in the treatment of sulfate-laden wastewater, yet their electron transfer efficiency remains a major bottleneck limiting system performance. This review systematically examines five enhancement strategies, including the photoelectric effect, bioelectrochemical systems (BES), conductive materials, electron shuttles (ES), and biostimulants. The bottlenecks are first classified into three key steps, namely direct electron transfer (DET), indirect electron transfer (IET) via soluble mediators, and direct interspecies electron transfer (DIET), and the specific targeting relationships of each strategy are established. On this basis, a five-dimensional comparative framework is constructed, covering core principles, energy demand, carbon source requirement, applicable scenarios, and technology maturity, and is extended with three engineering indicators, namely operating cost, secondary pollution risk, and long-term stability, to support practical decision-making. The synergistic mechanisms and performance gains of three mainstream combined strategies are then summarized, along with representative engineering cases. The results indicate that conductive materials and biostimulants show promise for engineering-scale application, BES is in the pilot-to-engineering transition, while the photoelectric effect and ES remain at the laboratory scale. Combined strategies can overcome the performance ceiling of individual approaches through multi-target synergy, but face common limitations including cost superposition and scale-up uncertainty. This review provides a systematic theoretical foundation and decision-making reference for strategy selection and process optimization in SRB-based wastewater treatment.