The effect of sonication at different frequencies on microbial disinfection using hypochlorite
Helen Duckhouse, Timothy J. Mason, S. S. Phull, Larysa Paniwnyk and J. P. Lorimer
Sonochemistry Centre, School of the Science and the Environment, Coventry University, Coventry, CV1 5FB, UK.
The effectiveness of bacteria kill by chlorination can be improved by increasing hypochlorite ... [Show full abstract] concentration but this may exacerbate other problems associated with the use of excess chlorine . One way to avoid this difficulty is by using ultrasound, which increases the efficiency of the biocide . Possible reasons for this improvement in the effectiveness of chlorination are:
(a) Dispersal of bacterial clumps making individual bacteria more available to biocide attack.
(b) Temporary weakening of cell walls making them more permeable to the biocide.
(c) Irreversible break down of the cell wall.
A remarkable frequency effect has been observed on the biocidal efficiency of sodium hypochlorite solution towards Escherchia coli suspensions. At 20kHz the improvement is best with simultaneous ultrasound whereas at 850kHz the improvement is best using ultrasound as a pre-treatment. The kill rate achieved for pre-treatment using 850kHz and simultaneous treatment using 20kHz are very similar . However the former involves less acoustic energy, as measured by calorimetry, and this suggests that the process improvement is more efficient.
We have continued our investigations in an attempt to elucidate the mechanism of the frequency effect. These include (a) changes in the volume treated in order to investigate the influence of acoustic power and (b) the effect of added solid particles as a method of determining the possible influence of the mechanical disruption of cell structure.
Helen Duckhouse thanks EPRCS for a Case Award in conjunction with Sonic Process Technologies Ltd.
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