Studies on ozonation of bulking activated sludge with SVI 286 ml/g in MLSS 3, 500 mg/l have been conducted to control the bulking characteristics by batch tests and continuous experiments of bench scale.
The results of batch tests showed that the optimum dosage to control sludge bulking was about 16.5-27.6 mg O
3/gSS and the optimum contact time was 3-5 minutes. But the settlement characteristics of activated sludge were deteriorated by the application of higher ozone dosage than optimum dosage. Adsorption isotherm could be obtained with cations such as ruthenium red dye and with a higher affinity for ECP alone than for the whole sludge. Freundlich isotherm model by ruthenium red dye adsorption method was clearly effective to measure and evaluate the characteristics of the ozonized sludge surface. Also, the result of continuous experiments showed that SVI values decreased from 286 ml/g to 100 ml/g during the course of continuous ozonation treatment for bulking sludge in the settling tank, and even after the stop of ozonation, low SVI levels i.e. less than 150 ml/g, could be maintained for a while, which means ozonation can create the sufficient condition of bulking control.
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