Enhancement of Anaerobic Digestion Operational Efficiency for Guar Gum Production Wastewater Using a Microaerobic-Biochar Coupled System

• • COD removal efficiency reached 90% under microaerobic-biochar coupling (0.2 mL/(g VS·d) micro-aeration, 15 g/L biochar, 37 °C), a 10.6 percentage point improvement over anaerobic control, demonstrating enhanced organic mineralization for high-strength industrial wastewater. • • Effluent propionate concentration was reduced to 0.15 g/L, a 98.4% decrease versus control, mitigating the key inhibitor in anaerobic digestion of 1,2-propanediol-rich wastewater, thus preventing acidification failure. • • Biogas production increased to 1.64 times that of the anaerobic control, with maximum methane content of 77.2%, indicating improved energy recovery and process stability. • • FT-IR and SEM analyses confirmed increased –OH, –CH2–, and C–O functional groups and formation of dense microbial aggregates dominated by long bacilli, evidencing biochar's role in enhancing microbial adhesion and syntrophic interactions.