Study On Algae Inhibiting And Removing Technology Based On Ultrasonic Principle

The algae bloom caused by the eutrophication of the slow flowing water body is one of the important environmental problems.The outbreak of water bloom not only damages the ecological balance,but also seriously affects the residents' drinking water safety.It has social signification to study the technology of algae inhibiting and removing.Due to the limited working distance and hardship in using of the domestic technology of ultrasonic algae inhibiting and removal,in this paper,the numerical simulation of ultrasonic field is carried out by COMSOL Multiphysics.The effects of ultrasonic frequency,loading voltage and other factors on the sound field are analyzed.The effects of ultrasonic algae and algae suppression technology on the application of ultrasonic algae removal are discussed.The effect of ultrasonic frequency,power density,action time,action mode and pH,these five parameters were studied with microcystis aeruginosa used as the experimental object and optimization of ultrasonic parameters were analyzed.On this basis,ultrasonic algae-suppressing device was designed for continuous operation in large area of water.The results shows that the sound pressure decreases rapidly with increasing distance,and the sound pressure is linear with the loading voltage.The higher the loading voltage is,the higher the sound pressure is.The higher the ultrasonic frequency,the more energy is absorbed by the water,and also leads to the fast attenuation in water,small distance of propagation,narrower main sound beam and the bigger the boundary line of the near field and the far field which means the better the directivity.When the ultrasonic frequency is low,the action area is large,and it is suitable for algae inhibiting and removing in large area of water.The experimental results shows that the higher the ultrasonic frequency,the better the algae removing effect,and the effect was stable after ultrasonic treatment for 36 hours.The higher the power density of ultrasound radiation,the better the effect of algae removing;When the power density is low,the algae cells are damaged by mechanical action and keep multiplication capacity after radiation 48h;when the power density of ultrasonic radiation is more than or equal to 0.05 W/mL,the effect of algae inhibiting will be saturated;if ultrasonic treatment time is too long,neither economic nor environmental protection;ultrasonic algae control effect is not affected by the pH;second ultrasound effect of algae control is significantly better.Under the low ultrasonic radiation power density,the microcystis density recovered after the cells were inhibited by ultrasound for 36h-48h.Ultrasonic algae inhibiting and removing device were optimized with parameters of ultrasonic frequency 20 kHz,ultrasound power density 0.0001W/mL,and ultrasonic interaction twice.The time interval was 36 h,each time was 1 min.It is expected the wild use of the device in China will promote the development of China's algae control technology,boarden water environmental management's mind,and generate social and economic benefits.