[Various effects on the activity of activated sludge by low intensity ultrasonic treatments with different parameter...

Aerobic activated sludge was used as experimental material. Specific oxygen uptake rate (SOUR), mixed liquor suspended solids (MLSS), COD ratio and lambda (deltaMLSS/deltaCOD) were taken as experimental indexes to indicate the changes of sludge activity and metabolism. The influences on activated sludge induced by ultrasonic treatments with different parameter combinations were studied by equal-distribution experiments about frequency, ultrasound intensity and irradiation time. The results indicated that the best parameter combination (28 kHz, 20 W/L, 2 min) leaded to an evident enhancement of sludge activity and reduced the sludge production at the same time. MLSS, as a vital factor which influences the ultrasonic treatment, was concerned in this study. To the sludge used in these experiments, the results of multilevel experiments showed that the MLSS of 3 000 mg/L induced to a relative highest performance after ultrasonic treatment with the best parameter combination. This article also hypothetically presented the mechanism of sludge activity enhancement stimulated by low intensity ultrasound.