Removal of coliform pollution from municipal wastewaters using ultrasound and chlorine dioxide

Synthetic and real municipal wastewater and biologically treated secondary effluent were disinfected with ultrasound (US), chlorine dioxide (ClO2), and their sequential combination using different ultrasonic powers. Results showed that ultrasound or chlorine dioxide alone did not provide sufficient bactericidal inactivations during 10-min disinfection period. Results also showed that the effect of combined US and ClO2 on E. coli and TC inactivation in synthetic wastewater and secondary effluent was additive indicating that the sequential combination did not act in a synergistic fashion. The enhanced bactericidal effects by the combined system were observed only during the disinfection of real untreated wastewater at 30 and 60 W of ultrasonic powers. E. coli and TC log inactivations by ClO2 in sonicated samples increased by up to a factor of 3-3.5, when compared with the bacteria log inactivations using ClO2 alone. The improved ClO2 disinfection following ultrasonic treatment was attributed to the presence of high particulate matter in wastewater and their break up under shock ultrasonic waves.Keywords: Chlorine dioxide, Ultrasound, Coliform, E. coli, Disinfection