Effect of Hydrothermal Pretreatment on Volatile Fatty Acids and Methane Production from Thickened Waste Activated Sludge

The main goal of this study was to evaluate the impact of hydrothermal pretreatment (HTP) on fermentation and anaerobic digestion (AD) of the Thickened Waste Activated Sludge. For this purpose, all samples were subject to the HTP under 5 Severity indexes extending from 3.00 to 5.00. The HTP temperature, pressure and holding time ranged from 150 to 240oC, 69 to 488 psi, and 5 to 30 min, respectively. The batch mesophilic acidification and biomethane potential tests were conducted in triplicates for all hydrothermally pretreated and none pretreated samples considering the food to micro-organism ratio of 1 g-TCOD/g-VSS. Results revealed that HTP improves the fermentation and AD of TWAS significantly. The maximum solubilization, volatile fatty acids (VFAs) production, and methane yields were 49%, 5.4 g COD/L, 227 mL CH4/g TCODadded, respectively. Also, it was found that the optimum pretreatment condition varied from one parameter to another, for solubilization, it was“200°C-10min”, however, for VFAs production, it was “190°C-10min”, and for methane production, it was “170°C-10min”.