Intensification of thermophilic anaerobic digestion of sewage sludge by thermal hydrolysis

Thermal hydrolysis (THP) combined with thermophilic anaerobic digestion (TAD) offers promising pathways for enhancing sewage sludge treatment. This study is among the first to directly compare THP as both pre- and post-treatment options for TAD. Pre-treatment of waste activated sludge (THP-WAS) and post-treatment of digested sludge (THP-DS) were evaluated on their impacts on process stability, biogas production, and sludge dewaterability. Pilot-scale trials at a wastewater treatment plant (WWTP) in Prague revealed that THP-WAS increased sludge solubilization but faced challenges such as volatile fatty acid accumulation, adversely affecting reactor stability and specific biogas yield. In contrast, THP-DS enhanced biogas production by 10%, improved sludge dewaterability, and achieved superior methane content (73.2%). Further research is needed to optimize THP parameters for reactor stability and to better understand interactions between hydrolyzed WAS and primary sludge.