Microwave vs. Conventional Thermal Sludge Pretreatment Technique: A Comprehensive Comparison Under Identical Thermal Profile

This research provides a comprehensive comparison between microwave (MW) and conventional heating (CH) sludge pretreatments under identical thermal (heating/cooling) profiles at below and above boiling point temperatures. The MW pretreatment was done using a high pressure lab-scale MW station. The CH pretreatment was performed using a custom-built pressure-sealed vessel which could simulate MW heating under identical heating/cooling profiles over a wide range of temperature (80, 120 and 160°C) and heating rate (3, 6 and 11°C/min). The effects of pretreatment method, final temperature and heating rate on solubilization of dewatered sludge cake (DWSC) as well as performance of mesophilic batch anaerobic digester were examined. No statistically significant difference was observed between the performance of MW and CH pretreatments in terms of sludge solubilization, biogas production and biodegradation kinetic rate (p-value>0.05), while statistically significant effects of pretreatment temperature and heating rate were proved (p-value<0.05).