Effects of Sludge Kind, Size and Structure on Sludge Anaerobic Fermentation

This study compared the anaerobic fermentation performance of aerobic floc sludge (AFS), AGS with different diameters (AGS200-500, AGS500-1600 and AGS>1600) and crushed AGS (CAGS200-500, CAGS500-1600 and CAGS>1600) to explore the mechanism of AGS anaerobic fermentation. AGS has higher extracellular polymeric substances (EPS) contents which can be used as a fermentation substrate, and the results of EPS dosing test also showed that EPS were favor for fermentation acid production. Furthermore, the anaerobic zone inside AGS accumulated many dead cells which can also be used as a substrate for fermentation directly. In addition, breaking the granular structure of AGS can improve the sludge hydrolysis and acidification. Mechanical crushing of the particle structure did not lead to the crushing of bacteria cells, but the degradation of EPS. Most importantly, crushing AGS increased the contact chance of hydrolysis enzymes and substrates by releasing hydrolysis enzymes from the inside of granules.