The isolation, identification of sludge-lysing thermophilic bacteria and its utilization in solubilization for excess sludge

Abstract

A novel strain of thermophilic bacteria with a highly efficient sludge dissolution performance was isolated from garden soil at 65°C in this study. The colony morphology, physiological and biochemical characteristics of the strain were investigated. The results showed that the strain was Gram-positive, small rod-shaped, sporulating and secreted extracellular enzymes (protease and amylase). The 16S rDNA analysis demonstrated that this strain had not been previously reported. Therefore, it was labelled Bacillus thermophilic bacteria AT07-1 (registration number: FJ231108). To evaluate its capability for excess sludge solubilization, a pure culture of the strain was used in sludge solubilization tests; an enhanced solubilization process was subsequently obtained. After 36 h digestion, the protease activity in the inoculated system reached 0.37 U/ml, an increase of 0.16 U/ml compared with the non-inoculated system (0.21 U/ml). The solubilization rate for volatile suspended solids reached 46.45% in 48 h after inoculation with Bacillus thermophilic bacteria AT07-1, which was 10.24% higher than the non-inoculated system, and which could meet the standard of sludge stability suggested by the US Environmental Protection Agency.