Majallah-i Dānishgāh-i ̒Ulūm-i Pizishkī-i Bābul (Dec 2011)
Performance of Ultrasonic Process on Removal of Fecal Indicator Bacteria of Escherichia Coli and Enterococcus Faecalis from Drinking Water
Abstract
BACKGROUND AND OBJECTIVE: Conventional processes of drinking water disinfection could not completely remove contamination indicator bacteria. So, application of new technologies like ultrasonic process has been considered for drinking water disinfection. In this study, the performance of the ultrasonic process on removal of E. coli and E. faecalis from drinking water was evaluated.METHODS: In this cross-sectional study, synthetic solution contained E. coli and E. faecalis with populations of 103, 105, 107 and 109 cfu/mL (Colony Forming Unit/ milliliter) were used. After microbial seeding, drinking water samples were exposed to ultrasonic waves with the cycle of 2, 6 and 10 Pulse/s in 5 and 10 minutes. A measurement criterion of the disinfection performance was removal efficiency of indicator bacteria. Microbial colonies were counted by McFarland and plate count methods. The ultrasonic power and microbial concentration in the process of inactivation of bacteria were compared by using McFarland method.FINDINGS: In this study, the removal performance of E. coli with colony density of 103 cfu/mL and the sonication cycle of 2 pulse/s was 1.1 log, while in the sonication cycles of 6 and 10 pulse/s was 3 log (p<0.009). Also, the removal performance of E. faecalis with colony density of 103 cfu/mL, the sonication cycle of 2 pulse/s and retention time of 5 min was 0.52 log which had significant difference in compared to the sonication cycles of 6 and 10 pulse/s which was 3 log (p<0.001). The removal efficiency of all bacterial populations was 3 log, in retention time of 10 min. By increasing the initial population of the bacteria, the performance of the disinfection process was significantly decreased (p<0.001).CONCLUSION: The result of this study showed that the ultrasonic process was effective in removal of E. coli and E. faecalis from drinking water and its efficiency was independent from bacterial population.
