Integrated Resource Recovery from Sludge for Synergizing Quorum Sensing and Interspecies Electron Transfer in Anaerobic Treatment

Anaerobic granular sludge (AnGS) plays a vital role in treating organic wastewater, yet its performance is limited by methanogens’ poor resistance and inefficient interspecies electron transfer. Emerging quorum sensing (QS) is a promising approach for regulating AnGS but relies on costly exogenous signaling molecules. In this study, an innovative functional material (AHLs/EPS@BC) was synthesized by extracting N-acyl-homoserine lactones (AHLs) and extracellular polymeric substances (EPS) from waste AnGS and loading them onto cycling biochar (BC). The AHLs/EPS@BC significantly improved the acid shock resistance of AnGS, restoring the chemical oxygen demand (COD) removal efficiency to 90.2–93.8%. The specific methanogenic activity (SMA) was maintained at 16.7–21.1 mL/(gVSS·h). Mechanistic studies reveal that the AHLs/EPS@BC composite enhanced AnGS stability and methanogenesis performance by integrating QS and direct interspecies electron transfer (DIET). The sustained release of AHLs mediates QS, restructuring microbial communities and stimulating EPS secretion to alleviate the acid shock. Meanwhile, the conductive BC and the induced quinone group, as well as highly expressed conductive pili, can establish the DIET process. A comprehensive life cycle assessment confirms the substantial environmental and economic benefits of this sludge reuse strategy. Overall, our study highlights the potential of in situ recovery of high-value components from waste sludge, offering a sustainable regulatory approach to AnGS for organic wastewater treatment.