Keywords: anaerobic digestion, hydrothermal pretreatment, biogas, volatile fatty acids, thickened waste activated sludge
Summary:The principal goal of this study was to evaluate the impact of different configurations of hydrothermal pretreatment (HTP) with anaerobic digestion (AD) as well as fermentation. Also, impact of solid content on AD of the TWAS was assessed. Two systems with different configurations were designed for this study. In first design HTP was applied before AD and fermentation and in second design HTP was applied after first stage of AD. Results revealed that hydrothermal pretreatment effect on two stage AD was more significant compared to the single stage. The cumulative methane yield for one stage AD was 701 mL CH4 / g VSSadded while it was 901 mL CH4 / g VSSadded for two stage AD. Also, the HTP before AD was proved to have higher methane yields compared to the application of HTP after first stage of AD. In terms of fermentation only, detected VFAs during fermentation of hydrothermally pretreated TWAS was 40% higher than that of raw.