[Enhanced hydrolysis of waste activated sludge by biosurfactant]

The effects of biosurfactant on the hydrolysis of waste activated sludge including reaction time, dosage of rhamnolipid and pH were investigated. It was found that the rhamnolipid could greatly reduce the surface tension of sludge hydrolysis liquid, resulting in the solubilization of organic solid and the release of extracellular enzyme. During the hydrolysis process, the concentrations of SCOD, soluble reducing sugar and soluble protein showed an obvious increase in the initial and then decrease later. Sludge hydrolysis process fitted to the first-order reaction dynamics within 6 h. At rhamnolipid dosage of 0.3 g x g(-1), the concentrations of SCOD, reducing sugar and protein after 6 h of hydrolysis increased from 371.9, 93.3 and 9.0 mg x L(-1) to 3 994.5, 800.0 and 401.7 mg x L(-1), respectively. The efficiency of sludge hydrolysis was improved with the increase of pH value, and the maximal concentrations of SCOD, reducing sugar and protein were, respectively, 5 249.9, 1658.3 and 597.1 mg x L(-1) at pH 11.