טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentRonit Simhony
SubjectSonication as a Method for Inactivation of Enteric Bacteria
in Water and Effluent
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Emeritus Narkis Nava
Professor Emeritus Kott Yehuda (Deceased)


Abstract

 



In the present study the possibility of using sonication as a method for inactivation of pathogenic microorganisms in water and effluent was investigated. In water the bacteria studied were: E. coli B, Shigella Sonnie , Salmonella, Typhimurium and E. coli O 157:H7. The acoustic intensity during water sonication was 7.8 W/cm2 . In effluents the bacteria studied were: coliform, Fecal coliform, Fecal Streptococcus, E. coli B Phages and total count were preformed. Effluents were taken from the activated sludge facility in the Haifa Municipal Sewage Treatment Plant. Acoustic intensity applied during effluent sonication was 11.7 W/cm2 .


The obtained results can be summarized as follows:

-          Sonication causes inactivation of the enteric bacteria in water. The effect of ultrasound on bacterial inactivation is very significant. The number of surviving bacteria in water after sonication, at a constant acoustic intensity, within defined time periods, depends on the initial bacteria count.

-          The acoustic intensity was studied during soniction of E. coli B, Shigella sonnie and Salmonella  Typhimurium in water . It was found that acoustic intensity has a significant influence on the bacterial inactivation rate.

-          Sonication causes inactivation of the enteric bacteria in effluents.

-          It was found that sonication of raw effluents, or raw effluents after centrifugation, or raw effluents after flocculation, at acoustic intensity of 11.7 W/cm2, during 30 minutes, causes a decrease of two orders of magnitude of the initial total count, decrease of two orders of magnitude of the initial coliforms and decrease of two orders of magnitude of the initial Fecal coliform.

-          Sonication of raw effluents, or raw effluents after centrifugation, or raw effluents after flocculation, with acoustic intensity of 11.7 W/cm2, during 30 minutes, causes a decrease of less than one order of magnitude of the initial Fecal Streptococcus and decrease of one order of magnitude of the initial E. coli B Phages.


The ultrasonic technology used has a significant potential to become an effective method for inactivation of enteric bacteria in water and effluents. The use of ultrasonic technology treatment for rehabilitation of infected groundwater or small water lakes seems to be very promising. The advantages of ultrasonic water treatment are primarily due to its simple apparatus requirements and mild operation conditions. The sonication inactivation can be achieved at ambient conditions, without the addition of chemicals to the treated water. Furthermore, soniction can simultaneously facilitate THMs compounds removal from the aqueous solution.