Study On Low Intensity And Low Frequency Ultrasound Influencing Activity Of Activated Sludge

The effects on activity of activated sludge caused by ultrasonic iradiation with low intensity and low frequency were studied through multi-parameters and multilevel experiments. The results of these experiments induced to the following conclusions: In the process of ultrasonic treatment, the main factors which influence SOUR (Specific Oxygen Uptake Rate) and dehydrogenases of sludge are ultrasound frequency and power. The ultrasonic promotion on sludge activity is finite. If take both performance and economy into consideration, power range of 5W~20W and processing time within 5min～25min are relative ideal.Ultrasonic treatment unit was incorporated into the experiments which simulated processing organic waste water with high concentration using activated sludge. SOUR, MLSS (Mixed Liquor Suspended Solids), COD removal ratio andλ(?MLSS/?COD) 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 or modes were studied by appropriate experiments about frequency, power input and irradiation time. Through these experiments, the best parameter combination was ascertained. The results indicated that the best parameter combination (28 kHz, 40W, 2 min) leaded to an evident enhancement of sludge activity and reduced the sludge production at the same time. MLSS influences the result of ultrasonic treatment, because variation of MLSS can influence the intensity and scope of ultrasonic cavitation. Repeated and interim ultrasonic treatments can restrain sludge growth and promote the removal of COD. If take both performance and economy into consideration, the best interval of treatments is 6h.The mechanism of promoting sludge activity by low intensity ultrasound was studied by some proper experiments. The results induced to the following conclusions: Low intensity ultrasound is able to enhance the adsorption capability of sludge. Appropriate processing with low intensity ultrasound can improve the efficiency of catalyze of dehydrogenase and activate the synthesis of dehydrogenase.