| Our research has confirmed ultrasonic promotion for sludge anaerobic/aerobic is feasible. This paper studied the mechanism of ultrasonic-anaerobic/aerobic sludge, analyzed the trend of index of EPS (polysaccharide, protein, DNA and total content), dissolved substances, proportion of EPS and dissolved substances (polysaccharides, protein and DNA), enzyme activities (protease activity, dehydorgenase activity) and bacteria density, provided the popularization and application of theoretical basis.Firstly, By using uniform design testing the effect of ultrasonic pretreatment conditions on oxygen/aerobic digested sludge. In the conditions of 28kHz, The optimal ultrasonic conditions was:15min ultrasonic time,0.1 W/mL density and 12h ultrasonic interval time, the performances of anaerobic/aerobic digestion were greatly improved, the removal rate of SS and VSS reached 37.97% and 42.45% after 10d digestion, which is higher than 10.5% and 20.2% of control sludge.Ultrasonic pretreatment of sludge digestion efficiency is obvious stimulative effect.Secondly, the variational trend of EPS index in sludge was studied through the biochemical analysis. The results of sludge anaerobic/aerobic digestion promoted by ultrasonic treatment showed that the variational trend of EPS index in sludge increased firstly and then fell off during 10d digestion, the maximum of protein, DNA and total content were appeared in the 2d, while the maximum of polysaccharides was came out in the 4d. The total content of EPS in ultrasonic sludge was more than the control sludge during 0-6d digestion, and then less than control in 6-10d because of a large amount of EPS and cellular substances had been released out. The dissolved substances concentrations were highly increased after ultrasonic treatment. The maximum of total concentrations in ultrasonic sludge was 34.61 mg·L-1 higher than the beginning, it was about 3.5 multiple of the increased concentrations of control's maximum, indicated that ultrasonic treatment could release EPS and cellular substances into the supernatant. The index proportions of EPS and dissolved substances in the ultrasonic sludge and the control were almost the same, indicating that ultrasonic could promote oxygen/aerobic sludge digestion but wouldn't change the index proportion of EPS and their dissolved substances.And then, the variational trend of enzyme activities in sludge was studied.The variational trend of enzyme activities increased at the beginning and then fell off after 10 days'digestion, the maximum value appeared in the fourth day. The protease activity of ultrasonic sludge was more than that of the controlled during 0-5d digestion. While the variational of dehydrogenase activity in ultrasonic sludge was almost the same compared with the controlled, suggesting that it couldn't represent ultrasonic promotion by sludge anaerobic/aerobic digestibility.At last, the group of EPS in sludge was studied through infrared spectrum. The infrared spectrum analysis of EPS showed that polysaccharide, protein and DNA were the major components of EPS in anaerobic/aerobic sludge, ultrasonic treatment wouldn't change the organic structure of them.The greatly release of soluble organics enhanced the consumed proportion of organics, markedly improved protease activity and the high-speed biological reaction, organic matter degradation ratio was improved greatly, as a result, the VSS removal rate in ultrasonic sludge was markedly improved.
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