Notice of RetractionEffect of ultrasonic pretreatment on disintegration of dewatered sewage sludge

The excess activated sludge is usually directly dewatered without digestion in most municipal wastewater treatment plants, which will pose potential threat to ecological environment due to its high content of organic matter. Therefore, there are the needs of centralized digestion of these dewatered sludges. The process of anaerobic digestion of sludge is restricted by its hydrolysis process, so the pretreatment is necessary to disintegrate the bacterial cells so as to improve anaerobic digestion. In this study, dewatered sewage sludge was pretreated by ultrasound to study the effect of organic matter dissolution. The results showed that with the increase of ultrasonic power, the effect of dissolution was improved, and more organic matters were transferred from the phase of solid to that of liquid. However, the rates of SCOD dissolution at different ultrasound power densities were different. When ultrasound power density was 0.8 W/ml and 1.67 W/ml, the rate was 0.279 mg/l·ml-1·J-1 and 0.280 mg/l·ml-1·J-1, respectively. When the ultrasound power density was 3.34 W/ml, the dissolution was better than the former two as the rate reached 0.698 mg/l·ml-1·J-1.