Pretreatment for anaerobic blackwater treatment: ultrasonication and thermal hydrolysis

Abstract

Anaerobic digestion of blackwater converts waste to energy. However, due to a low hydrolysis rate, the hydraulic retention time of a digester can be several days. Here, ultrasonication (30 min) and thermal hydrolysis (at 160°C for 30 min and 2 h) were tested as a pretreatment for accelerating the hydrolysis step. Pretreatment of blackwater with ultrasonication (30 min) and thermal hydrolysis (at 160°C for 30 min) increased the ammonia nitrogen (NH4-N) concentration in the blackwater from 1·16 to 1·46 and 1·51 g/l, respectively. Ultrasonication (30 min) enhanced the biological methane potential of blackwater from 0·48 to 0·62. Although thermal hydrolysis at 160°C for 2 h increased the soluble chemical oxygen demand concentration from 3·0 to 3·6 g/l, this process did not improve biological methane potential.