Improving the performance of ultrasonic horn reactor for deactivating microorganisms in water

摘要

The research on enhancing the performance of ultrasonic reactor for the purpose of microorganisms' inactivation is still ongoing. In this work, covering the cavitation chamber bottom with a corrugated surface as a source for heterogeneous cavities has been proposed as a simple modification to improve ultrasonic deactivation for ultrasonic horn reactor. Escherichia coli ATCC 25922 was used as a model microorganism in this study. Before using the corrugated surface, the configuration of the cavitation chamber was optimized experimentally in regards to cavitation chamber diameter and the depth of ultrasonic probe tip in the suspension. The optimization of the aforementioned factors was conducted on a basis of using constant suspension volume of 50ml. The depth of the ultrasonic probe tip in the suspension was changed from 2-10mm with a step of 2mm in overall depth of the suspension of 2cm, while the diameter of the chamber was changed using five Pyrex beakers with different diameters. The study was carried out using three level of ultrasonic intensity; low (17.56), intermediate (21.49) and high (24.17) W/cm2. The results of the optimization showed that increasing the diameter of cavitation chamber can decrease the log reduction of E.coli significantly. However, changing the depth of ultrasound probe in the suspension within the studied range was found to have only slight effect on the log reduction of E.coli in the order of approximately 0.5-log10. When using the corrugated surface with optimum chamber design, the results revealed that the corrugated surface can increase the log reduction of E.coli for the applied ultrasonic intensities. This effect was more discernable with low ultrasonic intensity than intermediate and high intensities.