Experimental Study On Microbial Inactivation Using Power Ultrasound In The Process Of Drinking Water Treatment

The raw water must be treated before being drunk by people for the sake of people s security. One indispensable step is microbial disinfection. All countries in the world have been adopting chlorination to kill microbe in water by now, and chlorination have played an important role in controlling the infection of diseases. But unfortunately lots of poisonous by-products were found in the treated water by further investigation. The poisonous by-products of course threat our health. Furthermore, with the fast development of modern agriculture and industry, more and more organic substance enter the water body, which cause the quality of water body increasingly worse. In addition, some species have the ability to mutate and can form spores which have greater resistance to chlorination. All these force people to seek for better disinfection techniques to kill bacteria in water.Recently, some researcher have been trying to use ultrasonic technique to deal with drinking water and find it has better effect to use ultrasonic technique in conjunction with other techniques such as heat, high pressure, ultraviolet irradiation etc. But it is also on the threshold about ultrasonic disinfection and lots of investigations need.In this thesis we studied primarily the sterilization effect of ultrasound by experiment and the following work has been done:(1) Designed processing bath, and measured the vibration system's efficiency from electricity into ultrasound power. It appears that the lower frequency vibration systems have bigger efficiency and their efficiencies change small with the variation of electric power; however, the efficiencies of the higher frequency vibration systems change greater with variation of electric power.(2) Studied the relation between the kill rate of bacteria and the electric power under the frequency of the 20.100 kHz and 31.560 kHz, respectively. Results showed that the low intensity ultrasound gives a rise in cell numbers as a result of declumping, then with the increase of ultrasound intensity the cell numbers decrease, but after power attains the certain number, the cell numbers rise again. This indicates that there is a optimal value about electric power.(3) Studied the relation between frequency and the kill rate of bacteria under the...