Experimental Study Of Pathogenic Microorganisms In Raw Water Killed By Hydrodynamic Cavitation Due To Venturi Tube With Variable Diffusion Angle

In order to solve the problem of safe drinking water and get rid of the potential harm to human health caused by traditional chlorination disinfection method with disinfection by-products,experimental study of pathogenic microorganisms in raw water killed by hydrodynamic cavitation due to Venturi tube with variable diffusion angle was carried out in this paper.Based on the variable diffusion angle Venturi-type hydraulic cavitation device,the mechanism of hydrodynamic cavitation killing pathogenic microorganisms was studied.Pressure device data collection system,high-speed camera and three-dimensional particle image velocimetry experimental equipment was used to studied cavitation flow characteristics,cavitation collapse pattern,velocity distribution,turbulence intensity,turbulent shear stress on cavitation flow segment of Venturi throat and diffuse.The effects of changing the throat velocity,diffusion angle an d throat length on the cavitation flow characteristics and hydraulic cavitation effect in the flow field were discussed.The experimental results showed that choosing the appropriate diffusion angle and throat length,increasing the throat velocity can enhance the cavitation effect of the flow cavitation area.In this study,a self-developed varied diffusion angle Venturi-type hydrodynamic cavitation generator was used to sterilize different raw water percentage in Shangtang River of Hangzhou.The total colony count and Escherichia coli were used as indicative microbes,and the killing effect of hydrodynamic cavitation on pathogenic microorganisms in raw water was characterized by detecting the killing rate of total colony count and Escherichia coli.The effects of diffusion angle,throat length,raw water percentage,cavitation number,throat velocity and hydrodynamic cavitation time on the killing rate of Escherichia coli and total colony count were studied in the experiment.The experimental results showed that choosing the appropriate raw water percentage,throat length and diffusion angle,lowering cavitation number or increasing the throat velocity and improving the hydrodynamic cavitation time can further increase the killing rate of total colony count and Escherichia coli in raw water.With the increase of killing rate,the absorbance value in water samples was rised.Absorbance is in direct proportion to the killing rate of microorganisms.The study uses a total of 20 kinds of Venturi tube combination,one of the best conditions for the combination of the length of the throat aspect ratio L/R=30,the diffusion angle of ?=4.3 °.Hydrodynamic cavitation can kill pathogenic microorganisms in raw water,which is a safe,efficient and novel technology of drinking water disinfection without disinfection by-products.