[Study on excess sludge solubilization in S-TE process under microaeration].

The effect of S-TE (solubilization by thermophilic enzyme) pretreatment on excess sludge solubilization and changes of chemical components under microaeration and different temperatures was investigated. The results showed that, two reaction mechanisms of enzyme-catalyzed reaction and thermal-hydrolyzed reaction were involved in the S-TE process, which began with depolymerization of sludge flocs by exoenzymes including proteases and amylases, followed by cell-walls and organic matters disintegration and hydrolyzation. The solubiozation process with thermophilic bacteria Bacillus stearothermophilus sp. AT06-1 addition was enhanced compared with the control (the process without the bacteria). Under the optimum temperature (65 degrees C), the solubilization rate of total suspended solid (TSS) and volatile suspended solid (VSS) reached 34.09% and 24.16% within 2 days respectively, 7.57% and 6.87% higher than the control. The results also revealed that under microaeration operation, the maximal soluble chemical oxygen demand (SCOD) of 4,531 mg/L and volatile fatty acid (VFA) of 2,319 mg/L were obtained, which would be beneficial to the followed anaerobic digestion process. At the same time the activity of protease was dramatically promoted. The protein released from the sludge was hydrolyzed, resulting in an increase of protein concentration at the early stage of the experiment and then a decrease at the later period.