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Environ Technol 2001 Apr;22(4):383-90 Related
Ultrasonic irradiation for blue-green algae bloom
Lee TJ, Nakano K, Matsumara M.
Institute of Applied Biochemistry, University of
Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-0006,
A novel application of ultrasonic irradiation for
rapid control of blue-green algae (BGA) bloom was
investigated. Potassium iodide (KI) experiments
demonstrated that frequency and input power are the
major factors that affect the ultrasonic irradiation
intensity. Short exposure (3 s) to ultrasonic
irradiation (120 W input power, 28 kHz) effectively
settled naturally growing BGA suspension. Electron
microscopy reconfirmed that sedimentation was caused
by the disruption and collapse of gas vacuoles after
ultrasonic exposure. Moreover, even after 5 min of
exposure to ultrasonic irradiation (1200 W input
power, 28 kHz) the microcystin concentration in BGA
suspensions did not increase. For the same input power
(120 W), a lower frequency (28 kHz) was found to be
more effective in decreasing the photosynthetic
activity of BGA than a higher frequency (100 kHz). The
sonicated cells did not proliferate when they were
cultured in conditions that simulated the bottom of
water bodies (i.e. with limited light (400 lx) or no
light and non-aerated or aerated (1 l min-1)).
Furthermore, ultrasonic irradiation did not only
collapse gas vacuoles and precipitate BGA, but may
have also inflicted damage on the photosynthetic
system of the BGA.
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