Abstract
Ultrasound is widely used to disinfect drinking water and wastewater due to its strong physical and chemical effects on microorganisms. The aim of this study was to investigate the effect of ultrasound on the destruction of
Mycobacterium strain 6PY1. Ultrasound waves (20
kHz or 612
kHz) were used to treat aqueous suspensions of
Mycobacterium at different volumes, initial bacterial concentrations, and power densities. At the same power density and the same exposure time, sonication at high frequency resulted in a lower destruction of
Mycobacterium sp. 6PY1 (35.5%) than sonication at low frequency (93%). The percentage of removal was not significantly affected by the volume of the irradiated suspension (150–300
ml) or the initial cell concentration (2.15
×
10
−3–1.4
×
10
−2
mg
protein
L
−1). At low frequency, the removal percentage of
Mycobacterium sp. 6PY1 increased with increasing the power density, with a constant level reached after a certain power density. At high frequency, the removal percentage of
Mycobacterium sp. 6PY1 increased with increasing the power density. The mechanism of cell killing was investigated by examining the effects of OH
radical scavengers such as sodium carbonate. At high frequency the presence of sodium carbonate suppressed the removal process. However, at low frequency the removal process was not affected, thus indicating that OH
radicals have a negligible role in this case. The latter result was supported by ten time’s H
2O
2 production at high frequency greater than that at low frequency.