Abstract:
The individual and combined effects of alkaline and ultrasonic pretreatment on both physical and
chemical properties and anaerobic biodegradability of waste activated sludge (WAS) were investigated
comprehensively in this study. The experimental results showed that both disintegration and anaerobic
biodegradability of WAS were significantly improved by the combination of alkaline and ultrasonic
(sono-alkaline) pretreatment. Besides, it was determined that the hydraulic retention time in anaerobic
digester can be shortened by half using this combined pretreatment. However, it was also determined
that sono-alkaline pretreatment was not feasible economically due to its high energy requirement.