Experimental Study Of Escherichia Coli Killed By Hydrodynamic Cavitation Due To Venturi Tube With Varying Throat Lengths

Water is one of the most important substances in life,our country has a serious water shortage,in the case of water shortage,in order to protect the normal production and living of residents,drinking water treatment is particularly important.At present,China's water treatment plant is generally taken by the way of chlorine disinfection,this method is economic effective,simple to operate.However,chlorine disinfection can not avoid yielding some by-products,in recent years,with domestic and foreign scholars' studies on chlorine disinfection by-products demonstrate that these by-products will cause three kinds of damage(Carcinogenic,teratogenic,mutagenic)to the human body,in order to eliminate this security risks,people began to focus on hydrodynamic cavitation disinfection technology.Hydrodynamic cavitation disinfection as a new type of drinking water disinfection technology is characterized by safe,efficient,green,and no disinfection by-products,which has potential prospects in the field of drinking water disinfection.In this paper,a self-developed Venturi-type hydrodynamic cavitation reaction device was used,the flow characteristics of the hydrodynamic cavitation working section were analyzed by the Three-dimensional Particle Image Velocimetry,and the distribution of the flow velocity,turbulence intensity and Reynolds stress in the hydrodynamic cavitation flow field were obtained.The YE6263 pressure data acquisition system was used to collect the pulsating pressure of working section during the operation of the cavitation device.Mathematical Statistics method was used to process the data,we got the relationship between the time-average pressure and the cavitation number in the cavitating flow field.The flow field state of the working section during the operation of the cavitation device was observed by PHOTRON APX-RS high-speed camera,The characteristics of cavitation in cavitating flow field were analyzed from the aspects of varying throat lengths and throat velocity.Based on above the flow characteristics research,Escherichia coli was selected as the indicative bacterium of pathogenic microorganism,and water samples containing E.coli were sterilized.Killing rates of E.coli were detected by agar plate counting method.Morphological changes in E.coli before and after cavitation were observed with a biological microscope.The effects of varying throat lengths,initial concentration,throat velocity,treatment time and cavitation number on the killing rates of E.coli were analyzed.The experimental results showed that the killing effect of E.coli was best at relative throat length L/R=60;Also,lowering cavitation number,increasing throat velocity,prolonging treatment time,and choosing a suitable initial concentration of E.coli can be helpful to improving the killing rates of Escherichia coli.