Ultrasound has been known to kill algae for at least 60 years, but it has not been used in practice until the last decade, mainly because of the high energy consumption of early ultrasonic equipment and the destruction of the ecological environment.
Ultrasound equipments used in early experiments have high power, low efficiency, and relatively large side effects. Some aquatic organisms are killed or seriously disturbed at the same time. The main reason is that early scientists did not realize the frequency of ultrasound on algae removal efficiency, blindly increase the power of the ultrasonic generator. Since the late 1990s, scientists have been working to optimize the ultrasonic algae control equipment to only harm algae and reduce the side effects on the environment and ecology.
It is found that different frequencies of ultrasound damage different algae and other aquatic organisms. Ultrasound at one frequency has a specific major group of injuries, with little impact on other aquatic organisms. Based on this fact, the scientists'new design only emits a combination of frequencies that do the most damage to algae, allowing the energy emitted to act on the algae to the maximum extent possible. This specific design makes the ultrasonic algae control equipment have a strong killing effect on algae under the condition of low power. Because the overall output power is small, and mainly for algae killing, this kind of ultrasonic impact on other aquatic organisms is very small. Many experiments have proved that this kind of special design of ultrasonic algae control equipment can neglect the impact of other aquatic organisms in the ecological environment, only for some fungi, fungi, Fusarium and so on.
The frequency of the device is controlled, but not a single frequency, because different algae are more sensitive to different frequencies. In order to ensure that algae killing equipment can control all kinds of algae, ultrasonic frequency is also a variety of advanced equipment generally has dozens of frequencies, and the frequency combination can be modified in the use of the scene.
In addition, ultrasound killing algae mainly causes damage to the inner cells of algae, does not destroy the cell membrane of algae, and does not stimulate algae to secrete toxins. Its main function is to destroy reproductive capacity and achieve the purpose of controlling algae. In the past ten years, there has been no increase in algal toxins caused by ultrasonic algal killing.
The opening and closing of ultrasonic equipment can be controlled by computer, and the opening and closing conditions can be set according to the application. In the application of environmental control, the concentration of chlorophyll-a can be used as the control condition to avoid the impact of excessive ultrasound on the environment. When the concentration of chlorophyll-a exceeds a set value, the system can start ultrasonic algae killing, when the concentration of chlorophyll-a is lower than a set value, then stop killing algae. In this way, there is a certain density of algae in water, but not at the level of damage. Algae control before the outbreak, rather than wait for algae outbreak after killing.
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