Preventive inhibition mechanism of algae by ultrasound based on analysis of physiological characteristics

Blooms of cyanobacteria cause ecological imbalance, killing a large number of water plants, fish and other aquatic organisms. In addition to easily cause algae toxin emission, the traditional processing method has drawbacks of short period of time and high energy consumption. Ultrasonic technology, as the environmental and effective method, is put forward to control the algae biomass. However, most studies based on inhibitory effect of ultrasound irradiation on algae were conducted at the algae photosynthesis system, the physiological activity of other indicators was not in-depth studied, and most of which were the short-term effects with unknown timeliness. The objective of this paper was to explore the suitable ultrasonic parameters to remove algae and the influence of ultrasonic frequency and power on physiological activity both from physiological activity and biomass control of algae cells. The results showed that the physiological and metabolic activities of algae were lower and the number of intact cells decreased after ultrasonic radiation. The proportion of damaged cells was proportional to the ultrasonic power density. DNA fragments were not detected after ultrasonic irradiation and DNA chain structure remained complete. The effects of ultrasonic parameters on algae density were also studied. When the power density was 0.02 W/mL, the effect of treatment under ultrasonic frequency of 40 kHz was better than that of 20 kHz and 100 kHz. It is suggested to use ultrasonic treatment with the frequency of 40 kHz and power density of 0.0245 W/mL to treat the blue-green algae.