Experimental study on the effect of ultrasonic waves on flocculation and sedimentation of cohesive sand

Abstract Sediment flocculation and sedimentation is a common phenomenon in estuarine coastal areas, and its sedimentation characteristics are one of the key contents of sediment transport research. In order to realize the purpose of high turbidity sediment flocculation without affecting the water quality, the authors propose a method to promote the flocculation and sedimentation of viscous sand to realize the separation of water and sand - ultrasonic-assisted flocculation and sedimentation method. Flocculation and sedimentation of viscous sand was studied by ultrasonic waves, and the results showed that: (1) when the concentration of sand content was 29 ~ 79%, the rate of flocculation and sedimentation of viscous sand was V natural > V ultrasonic waves + natural, but compared with natural sedimentation, the turbidity of the water quality was significantly reduced by the flocculation and sedimentation of ultrasonic waves and then natural sedimentation; at the same time, due to the pulsating vortex generated by the ultrasonic waves, the algae in the water body and other At the same time, due to the pulsating vortex generated during the ultrasonic action, other impurities in the water body such as algae floated on the water surface, which had the effect of removing algae in the water; (2) when the concentration of sand content was 41%~52%, the ultrasonic action prompted the viscous sand to produce the best flocculation and sedimentation effect, which corresponded to the clear and muddy interface with the settling height of 3.05 ~ 3.45 cm, and the rate of settling was 0.161 ~ 0.173 cm/min; (3) under the action of ultrasonic action, the water content of water W top > W middle > W middle, and then natural settlement after flocculation and sedimentation were achieved at different times. (3) Under the effect of ultrasonic waves, different time corresponds to different layers of wet substrate with water content Wupper > Wmiddle > Wlower, and dry substrate with water content Wupper < Wmiddle < Wlower. The research results can provide research and technical references for the study of flocculation kinetics and the treatment of high turbidity sandy water bodies.