Abstract
A disinfecting method has been considered by ultrasonic irradiation of water in the presence of TiO2. Titanium dioxide in the rutile-granule form was used as a catalyst in order to generate hydroxyl radicals for cell killing. Escherichia coli and Legionella pneumophila were used for kinetically investigation of cell destruction process. Significant decrease in the concentration of viable cells was observed during irradiation in the presence of TiO2. About 98% reduction in the concentration of viable cells could be obtained in the presence of 1.0 g/ml TiO2 during 30 min of irradiation, while only 13% reduction was observed in the ordinary ultrasonic irradiation system. The rate of cell killing was higher in the presence of TiO2 comparing to Al2O3. The rate of disinfection was proportional to the amount of TiO2 used in the irradiated samples. There was no significant effect of cell concentration on the cell-killing rate in the range of 103 to 107 CFU/ml. Mechanism of cell killing was further investigated by examining the effect of hydroxyl radical (*OH) scavengers. Ascorbic acid, histidine and glutathione were used in the irradiating samples as radical scavengers. The rate of disinfection was decreased in the samples containing these radical scavengers. Also, a continuous irradiating system was devised and applied for high throughput water disinfection process. Contaminated water containing E. coli was disinfected successfully within two hours of irradiation in the continuous system.
