Ultrasound And Circulation In Water Sterilization And Its Biological Effects

As the UN environment and development institution pointed out, the disease of eighty percent of human beings was involved with bacterium infection, over 60 percent of which was spread by drinking water. Chlorinating sterilization of water has becomed to be the most widely used and full grown technique among drinking water sterilization methods due to its strong antisepsis and sterilization ability and persistence sterilization function, as well as its low antisepsis system investment and run price. Further in-depth study shows that use of chlorine disinfection has a certain extent threat on human health. Therefore, people began to search for new, safer and more reliable methods and techniques in drinking water disinfection.With the developed of ultrasonics, people begin to concatenate ultrasound and drinking water sterilization. Although compared with other sterilization, ultrasound has better effection, but the sterilization of ultrasound also is not clear. However, ultrasonic is a kind of high cost enrage, so the expense of adopting ultrasonic for sterilization is high. And it is generally difficult to achieve project amplification. It is necessary to explore the mechanism of ultrasonic sterilization and find a kind of ultrasonic sterilization technique with low emerge consume and easy to achieve project amplification.In this experiment we initially discussed ultrasound-circulation sterilization system and the chief work we do was as follows:(1) The ultrasound-circulation sterilization system disposal bath we designed and manufactured, which not only carry through ultrasound experiment separately, but also ultrasound circulation take action at the same time.(2) By useing ultrasonic treatment system, we searched the regulation of kill rate of Escherichia coli with frequency, power, or processing time, confirmed the results accord with previous studies. It is found that the sterilization effectiveness is best when deal with 45min at the same time when the frequency of ultrasonic treatment system is 20kHz and the power is 25 W in the orthogonal experiment we designd. Owing to the frequency is the most significant influencing factor that we observe the sterilization rate changing with air input through controlling air input while the system is 20kHz, 33kHz. The results of the experiment indicate that the ultrasound-circulation system with different frequency has corresponding optimum air input. In addition, the sterilization effectiveness of the ultrasound air circulation is much better than the ultrasound alone. The factor of air input in designing orthogonal experiment was taken into account and the results of the experiment show that when the nominal frequency of the handing system is 33kHz, the power is 25W, the air input is 0.41/min and the dealing time is more than 30min, the sterilization rate is the best. The entering of air has influence on the significant factor. At last, when dealing Escherichia coli with ultrasound ozone circumfluence system, the sterilization rate of the ultrasound ozone circumfluence is much better than the ozone when the dealing time is short. However, when the time is long, the sterilization effectiveness is a little better.(3) We used ultrasound-circulation system, respectively study the regulation of killing rate of Staphylococcus aureus and killing rate of Bacillus subtilis with frequency, power, or processing time. We used ultrasound; ultrasound with air circulation, ultrasound with ozone circulation processing systems studied these two bacterias' difference respectively. The result found E.coli is not too easy to be killed than those two kinds of bacteria above.(4) We observed the surface morphology of the original E.coli and that was treated by ultrasound by atomic force microscopy and discussed primarily mechanism of ultrasound sterilization. The death of the E.coli was due to their broken even exfoliated cell wall and leakage of intracellular material. The E.coli lossed self-protection capacity due to the ultrasonic cavitation. Besides, because of the shedding of cell wall the ultrasonic cavitation directly acting on the bacterial cell membrane can also make them died.