Reducing Sludge Viscosity and Improving Dewaterability through a Thermochemical Hydrolysis Process

Thermal hydrolysis pre-treatment of sludge for anaerobic digestion increases biogas production, enhances volatile solids reduction, and improves dewaterability of digested sludge. This study reports the performance of a thermochemical hydrolysis process (TCHP) that utilizes heat (60°C- 70 °C) and sodium hydroxide for cell lysis. The objective of this study is to evaluate the impacts of implementing the TCHP on viscosity and floc morphology of thickened waste activated sludge (TWAS), dewaterability of anaerobically digested sludge, and biogas production. Cell lysis of TWAS was confirmed by microscope examination. Dewaterability of digested sludge was improved on full-scale dewatering centrifuges. The current data suggest at least 5-fold reduction of dynamic viscosity of WAS by thermal chemical hydrolysis treatment. Overall, the TCHP effectively hydrolyses TWAS and increases dewatered cake solids.