Abstract: In order to improve the efficiency of disintegrating excess sludge and then to improve the performance of sludge biodegradability by using ultrasonic cavitation， a program of disintegrating excess sludge by ultrasonic cavitation after a short anaerobic treatment was proposed. In the experiment， excess sludge was treated 0~6days by anaerobic digestion and then disintegrated by ultrasonic cavitation. The results show as follows: with increasing of anaerobic digestion time， the properties of sludge change greatly， for example， the concentration of chemical oxygen demand(COD)and peptidogly can increase significantly， while the pH value drop observably. The efficiency of using ultrasonic cavitation method to disintegrate excess sludge after a process of anaerobic digestion is better than disintegrating excess sludge directly. For example， the result of disintegrating the excess sludge treated 6 days by anaerobic digestion shows that the concentration of COD is 99.3 times of the sludge without disintegrating， and 9.5 times of excess sludge without anaerobic digestion. This study considers that anaerobic digestion can reduce the difficulty of sludge disintegrating and the process of anaerobic digestion can significantly improve the intensity of ultrasonic cavitation to a large extent. Therefore， the process can achieve the aim of disintegrating the excess sludge efficiently.

Key words: anaerobic treatment, ultrasonic cavitation, excess sludge, sludge disintegrating, pretreatment