Characteristics of advanced anaerobic digestion sludge-based biochar and its application for sewage sludge conditioning

Abstract

The utilization of sludge-based biochar, characterized by abundant pore structures, proves advantageous in enhancing sludge dewatering performance. In this study, advanced anaerobic digestion sludge underwent pyrolysis to produce biochar, subsequently employed for sludge conditioning. Results revealed that biochar, obtained at 800 °C, exhibited the highest specific surface area (105.3 m2/g) and pore volume (0.17 cm3/g). As the pyrolysis temperature increased, the sludge's functional groups tended to aromatize. When used to condition sludge, particularly at a 20 % (dry solid) dosage, biochar significantly reduced sludge capillary suction time and floc size. The addition of biochar enhanced the conditioning effect of cationic polyacrylamide by absorbing extracellular polymeric substances, creating water molecule channels, and forming skeletons for sludge flocs. These findings introduce a novel approach to sludge reuse and provide valuable data supporting the use of biochar as a sludge conditioner.