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In order to solve the problems of long sludge retention time and low efficiency in traditional sludge fermentation process, a new sludge pretreatment technology based on the mechanical stirring was proposed in this study. The effect of mechanical pretreatment on excess sludge fermentation was investigated. The results showed that mechanical pretreatment promoted the sludge flocs disinegration and cell lysis. When the mechanical stirring intensity was 21 000 r/min (pretreatment-1) and 35 000 r/min (pretreatment-2),the sludge particle size decreased from 66. 7 μm to 21. 9 μm and 16. 4 μm, and sludge disintegration degree was 10. 9% and 16. 9%, respectively. The sludge fermentation was improved by mechanical pretreatment, the yield of soluble chemical oxygen demand ( SCOD) and volatile fatty acids (VFAs) was significantly increased with the increasing of mechanical stirring intensity. The yield of SCOD and VFAs reached the maximum,when sludge retention time was 6 d. The maximum concentration of SCOD and VFAs were 5 102 and 3 469 mg/ Lin pretreatment-2 group, which were 96. 2% and 93% higher than those of the control group. The high-throughput sequencing analysis showed that microbial community composition was influenced by mechanical pretreatment. Firmicutes is the dominant bacteria in the fermentation system. The relative abundance of Firmicutes in the pretreatment-1 and pretreatment-2 was 88. 33 % and 96. 54 %, respectively, which was significantly higher than that of the control group (84. 38%),thus increased the yield of SCOD and VFAs. [ABSTRACT FROM AUTHOR]

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