Author(s): MH Dehghani, AH Mahvi
The current available strategies to inhibit growth of algae population include chemical addition, flushing with clean water, selective discharge of nutrient-rich water and decomposition of thermal stratification and biological treatment. However, some of these treatments have shortcomings, foremost of which is the generation of secondary pollutants. For example, chemical treatment (algaecides) may show immediate effect but this process may also indirectly kill or destroy other organisms due to the sudden release of toxic chemical components from the algae. Therefore, alternative methods for the control of algae population in water supplies are required. A novel method that is proposed is the use of ultrasonic irradiation. Ultrasonic irradiation in a liquid medium has been used for many years to lyse biological cells. Ultrasonication may have the potential to reduce their capacity to float and control their buoyancy thereby reducing their concentration near the surface of water bodies and lesson their growth and survival. Ultrasonication may also inhibit or reduce growth of algae population through its affect on metabolic processes. Application of ultrasonic irradiation for removal of algae population was investigated. Experiments demonstrated that frequency and input power are the major factors that affect the ultrasonic irradiation intensity. Short exposure (150 sec) to ultrasonic irradiation (155 W input powers, 42 kHz) effectively settled naturally growing algae suspension. Sedimentation was caused by the disruption and collapse of gas vacuoles after ultrasonic exposure. Moreover, was found to be more effective in decreasing the photosynthetic activity of algae population. This research will provide basic information on the fundamental of ultrasonic irradiation as a novel means for algae population control.