Experimental Study Of Killing Pathogenic Microorganism By Hydrodynamic Cavitation Due To Multi-orifice Plates With Different Orifice Shapes

With the improvement of the standard of living,the water quality requirements are increasing.Industrial development brings about a variety of water pollution problems.Traditional water treatment methods have their respective drawbacks so that they may not be there to meet the development of environment needs.So a new efficient,no secondary pollution and green water treatment technology is badly needed.As a new method of water treatment,hydrodynamic cavitation disinfection technology cannot only effectively kill the pathogenic microorganisms of water body,but also has the characteristics of safety,efficiency,green and economy.The application of hydrodynamic cavitation technology had become a research focus in the field of water disinfection.Cavitation is a complex and random phenomenon in fluid,the disinfection mechanism of hydrodynamic cavitation has been a difficult problem of the study.How to adjust the hydraulic parameter to maximize efficiency is the new direction of water treatment technology research.A self-developed hydrodynamic cavitation generator with multi-orifice plates in the Hydraulics Laboratory at Zhejiang University of Technology was used toproduce stable cavitation and sterilize raw water.The experimental research can be divided into three parts: the first part is the analysis of flow field characteristics of hydrodynamic cavitation generator;the second part is the experimental study on the disinfection of raw water by hydrodynamic cavitation;the third part is hydroxyl radical capture experiment.The details are as follows.(1)PIV can capture flow field characteristics and analyze characteristics of turbulence intensity and Reynolds stress in the hydrodynamic cavitation generator with multi-orifice plates of different shapes.Pressures in hydrodynamic cavitation generator were measured by the pressure data acquisition system of SINOCERA-YE6263.The influence of operation parameters and geometrical parameters on the flow field characteristics of the hydrodynamic cavitation is analyzed.(2)The hydrodynamic cavitation generator with multi-orifice plates was used to sterilize raw water in Shengli River of Hangzhou.The result of disinfection was characterized by the total colony,total coliform,Escherichia coli,TOC,TN,ORP,etc.The effects of initial water concentration,treatment time and geometrical parameters on the disinfection results were studied and the optimum hydraulic conditions were explored.The experimental results showed that increasing the orifice number,decreasing the orifice size,improving orifice arrangement and choosing the appropriate initial concentration could further increase the killing rates of pathogenic microorganism in raw water.The best disinfection effect was reached with hydrodynamic cavitation generator with triangleinterlacing 25-multi-orifice plates(3)With spectrophotometry,methylene blue was used to detect hydroxyl radical production during operation of hydrodynamic cavitation.The effects of processing time and parameters of different orifice parameters on the production of hydroxyl radical were studied.It is verified that the concentration of hydroxyl radical increases with time.Hydrodynamic cavitation generator with small hydraulic radius,large number of orifice,small orifice and interlacing arrangement can provide optimal hydraulic conditions for producing more hydroxyl radical.Overall,hydrodynamic cavitation is a high efficient,no secondary pollution,green disinfection new method.