Sludge Hydrolysis by Mechanical, Thermal, and Chemical Disintegration

Sludge hydrolysis is the most applied supporting process for anaerobic stabilization of sewage sludge. The aim of sludge hydrolysis is to prepare the sludge for the process of biodegradation; while decreasing the viscosity of sludge, the soluble COD of the sludge is increased with this process (Bishnoi, Effects of thermal hydrolysis pre-treatment on anaerobic digestion of sludge. Master thesis, Virginia Polytechnic Institute and State University, 2012). Specific biogas production ratio over the removed volatile suspended solids is related with the composition of the solids structure. In this way, the utilization of hydrolyzed sludge in anaerobic digesters provides a higher biodegradation rate in comparison to conventional anaerobic sludge digestion (Bishnoi, Effects of thermal hydrolysis pre-treatment on anaerobic digestion of sludge. Master thesis, Virginia Polytechnic Institute and State University, 2012). Resulting of higher loading rates in digesters, reducing the volume needed for anaerobic sludge digestion process via reducing the stabilization time and sludge volume fed to digesters, increased biogas production, and pathogen free and stabilized biosolid products are benefits of the system. The biodegradability of sludge solids can be improved by sludge hydrolysis resulting in solids solubilization. Finally, dewatering after digestion is substantially improved. To improve digestion performance including high specific biogas production, the feasible sludge hydrolysis methods are mechanical, thermal, and chemical sludge hydrolysis methods.