Experimental Study On The Inactivation Of Escherichia Coli By Hydrodynamic Cavitation Due To Triangular Multi-orifice Plates

Recently,China’s economy has a fairly rapid development,while environmental pollution has become increasingly serious.Now,people have more attention on those problems which is posing a threat to their health,especially drinking water issues,however the standard of drinking water which is treated by the technique of conventional disinfection cannot meet the new standard of drinking water.Hydrodynamic cavitation technology,as a new processing method in recent years,be characterized by environment-friendly,high efficiency,energy saving,no disinfection by-products and so on,it shows high research value and a broad application prospect.The experiment of hydrodynamic cavitation on disinfection was investigated based on a self-developed reactor in the Hydraulics Laboratory at Zhejiang University of Technology,Escherichia coli that is the pathogenic microorganism was chosen as the indicator bacteria,and the bacteria were killed by hydrodynamic cavitation due to three types of triangular multi-orifice plates in different conditions.Time-averagepressures of the flow behind multi-orifice plates were measured with a pressure data acquisition system,the water samples were collected in the process of cavitation and the number of E.coli(Escherichia coli)was cultured in agar plate,the changes in the morphology were observed by using biological microscope,and the concentrations of water samples were analyzed by the ultraviolet spectrophotometer.The effects of cavitation number,orifice velocity,initial concentrations,number of orifice,arrangement of orifice and size of orifice on the disinfection of E.coli were analyzed,and the bactericidal mechanism of E.coli by hydrodynamic cavitation was described,the conclusions are as follows:(1)Time is not the restriction in the growing of the bactericidal rate of E.coli,and the rate increased with the time of hydrodynamic cavitation until it reached 100%.(2)The lower cavitation number in the flow behind multi-orifice plates,the better effect of hydrodynamic cavitation could be made,and the higher bactericidal rate of E.coli could be reached.(3)With the same operating condition,the higher orifice velocity,more numbers of orifice or using staggered arrangement of orifice instead of board arrangement of orifice can make an better effect on the inactivation of E.coli by hydrodynamic cavitation due to triangular multi-orifice plates,the first multi-orifice plate is the best one in the effect of disinfection by hydrodynamic cavitation due to triangular multi-orificeplates.(4)The bactericidal mechanism of E.coli by hydrodynamic cavitation contains physical and chemical interaction that was caused by mechanical effects,and the physical interaction include impact and resonance damage,the chemical interaction include thermal effect and oxidation.