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The disposal of waste activated sludge (WAS) accounts for approximately 60 ％ of wastewater treatment plant operating costs. In this study, according to the reaction time and water quality parameters, ultrasonic hydrolysis of WAS is divided into three stages, including floc-disintegration (0–25.2 kJ/g TS), cell-disruption (25.2–36 kJ/g TS), and cell-degradation (over 36 kJ/g TS). The results show that more than 70 ％ carbon distributes inside the cell, which also contains 63.8 ％ protein enhancing denitrification capacity. Moreover, cell-degradation hydrolysate has a higher proportion of readily biodegradable COD, indicating that intracellular organic matter is more capable of denitrification than extracellular. Therefore, the optimal ultrasonic operating range is Es = 36–72 kJ/g TS as carbon source, and obtain the hydrolysate with high ratio of soluble chemical oxygen demand to total nitrogen for denitrification. Furthermore, this study supports the comprehensive interpretation of ultrasonic 
hydrolyzed WAS and the characteristics of hydrolysate as carbon source for enhancing denitrification.

Author：游博丞,黃政中,莊順興
★Article source：Bioresource Technology