About Ultrasonic Algae & Biofilm Control
Various ultrasound devices for control of algae and bacteria have been produced starting in the early 1900s. However, the recent practical use of such tools is driven by the technological improvements made in the last ten years. The commercial stimulus caused by the lack of herbicides, for control of algae, and the growing public perception that nothing should be added to water, has lead to the development of a new generation of ultrasound devices for water treatment.
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing (approximately 20 kHz). Low frequencies are in the range of 9-60 kHz and high frequences are over 130 kHz. The use of ultrasound has many industrial and medical applications. Since the late 1990s, ultrasonic waves have been used in water treatment for enviromental remediation of algae blooms. More recently, the technology has been effective in the reduction of biofilm in cooling tower circulation systems. A transducer converts electrical energy into vibratory energy of a specific amplitude and frequency. Water is the medium in which the waves traverse.
Most algae including blue-green react to ultrasound frequencies between 20 and 60 kHz, but exposure time and pulse length are also important variables. The energy which passes through the wall of these very simple single cells stimulates conditions that propagate the formation of oxygen radicals. This reaction causes loss of structural integrity of the cell and cellular collapse resulting in cell death. Denaturing of toxins usually occurs during this process.
- By JoAnn Sanborn, February 2, 2011 -