The effect of acoustic cavitation on Chlorophyceae from effluent of wastewater treatment plant.

The Chlorophyceae are a large and important group of green algae. They include some of the most common species, as well as many members that are important both ecologically and scientifically. When abundant in the water, they can rapidly cover the surface of sand filters and drastically reduce the length of filter runs. Also, tastes and odors are caused by the release of certain compounds by both living algae and dead and decomposing algae. This study will provide basic information on the fundamentals of acoustic cavitation as a new technology for control of Chlorophyceae growth. This technology is an attractive means to improve water quality because of the simplicity of the system and no production of toxic by-products. The inactivation of Chlorophyceae is mainly due to cavitation. Cavitation is a primary mechanism of ultrasound waves that occurs when the gas vesicles are acted upon by sufficiently intense ultrasound waves of different frequencies. Waves collapse gas vacuoles and precipitate Chlorophyceae. Also damage is inflicted on the chlorophyll of Chlorophyceae. Experiments have been carried out using ultrasound reactor in a laboratory pilot plant, to investigate the effect of acoustic cavitation. The results show that increasing the short exposure to waves has a considerable effect on destruction of Chlorophyceae growth and results in the loss of buoyancy. At 42 kHz it is shown that 100% of the Chlorophyceae can be destroyed in 130 seconds.