Experimental Study On Pathogenic Microorganisms In Raw Water Inactivated By Hydrodynamic Cavitation Due To Venturi Tube With Variable Throat Length

The traditional drinking water chlorination disinfection technology,not only generates disinfection by-products(DBPs),but also results in increasing resistance of microorganisms in water.Therefore,there it has gradual developed a new generation of drinking water treatment technologies based on physical disinfection and supplemented by chemical disinfection.Among them,the hydraulic cavitation technology uses micro-jet,shocking wave and shearing action of cavitation flow to kill pathogenic microorganisms in raw water,which has paid the community attention because of its advantages of fast,high efficiency,no disinfection by-products.Inactivation of pathogenic microorganism in raw water was experimentally investigated by using the Venturi tube with variable throat length(L/R)as the reactor of hydrodynamic cavitation,which was designed in the Hydraulics Laboratory.The main contents of this experiment are divided into two stages:In the first stage,in order to explore the cavitation strength?cavitation mechanism and cavitation characteristics of Venturi tube with variable throat length,in this paper,we used the three-dimensional high-speed particle speedometer PIV?SINOCERA-YE6263 pressure dynamic data acquisition and testing system and high speed camera to observe the flow velocity?turbulence intensity?turbulence shear stress and pressure data of the Venturi tube.In the second stage,in order to explore the actual sterilization effect on raw water pathogenic microorganisms of Venturi tube hydraulic cavitation reactor with variable throat length,in the experiment,the raw water was diluted and arranged to experimental samples at different initial concentrations according to certain concentration gradient.The total number of colonies in the water sample was counted by the plankton count frame and the biological microscope.The number of colonies of Escherichia coli in the water sample was cultured and counted by EMB selective medium.All of this datas were recorded as the basis of theoretical analysis.The effects of the initial concentration of raw water,the flow velocity of the orifice,the time of hydraulic cavitation,the flow field pressure and the aspect ratio of the throat on the inactivation rate of pathogenic microorganisms were studied experimentally.The experimental results show that the hydraulic cavitation technique can quickly kill the pathogenic microorganisms in raw water;under the condition of double pumps,the removal rate can reach 100%,and the removal rate of total plankton in raw water can reach more than 70% after 20min;don't produce disinfection by-products compared with the traditional drinking water treatment process currently in use,is a very good application prospects of drinking water disinfection of new technologies.