Effect of two-step thermo-disintegration on the enhancing solubilization and anaerobic biodegradability of excess waste sludge

The effectiveness of the pretreatment with a novel two-step thermo-solubilization system (TSTS-sys) on the disintegration of excess waste sludge (EWS), as well as the biogas (CH4) production efficiency of the following anaerobic mesophilic digestion, was experimentally evaluated. Carbohydrate was solubilized higher than proteins, and the concentration of VFAs increased also after pretreatment with TSTS-sys. CH4 was produced in the rate of 322 mL CH4 g−1 VS feed from the pre-treated EWS at 180 °C for 60 min operation. The CH4 composition ratios in the produced biogas were averaging 55.3 ± 076, 62.8 ± 097 and 71.2 ± 1.03% for control 1, 2 and the second step of TSTS-sys, respectively. The CH4 production rate of pre-treated EWS with the two step thermal solubilization of TSTS-sys was enhanced by 63.9% and 19.5% higher compared to the control 1 and 2, respectively. The additionally enhanced biogas production rate was still insufficient to cover the energy balance deficit caused by the pre-treatment. In this study, two-step thermal solubilization of TSTS-sys showed to be an efficient feasible pretreatment for enhancing the disintegration of EWS.