Hello,

Ultrasound intensity is an important parameter of sonication. The higher ultrasound intensity is the strong cavitation effect and biofilm remove. To achieve decontamination of bacteria high intensity and low frequency ultrasound is usually used. I am justify to removal of surface bacteria with the help of sonication.

1. Ultrasound of 20 kHz was applied in different sonication time (5 & 60 min) in 15degree C with 40% power amplitude.

Because I have done the sonication on wastewater. That time, I have keep the sonication horn 22 KHz at 40% power amplitude for 1 hour.

Hi,

As mentioned above by Mr. Yogesh Jawaharlal Yadav, the action of ultrasound is based on the phenomenon of cavitation, cavities containing gases under negative pressure. When these waves encounter a solid surface, they implode, releasing a high pressure of up to 100 bar and forming micro-jets. The implosion effect is used to remove dirt from solid surfaces.

There are different types of cavitation. Acoustic cavitation is caused by high intensity sound. Power ultrasound used for cleaning is characterised by high intensity and low frequency. Cavitation occurs when the energy produced is able to overcome the cohesive forces of the liquid.

The effect of ultrasound increases with power up to a certain threshold due to the creation of a shield of bubbles developing on the emitting surface. If the equipment does not have a power controller, it is possible to artificially increase the power by reducing the volume of the bath. Furthermore, low frequencies are known to favour physical effects. A frequency lower than 50 KHz is recommended for cleaning. Increasing the temperature decreases the effectiveness of ultrasound. Due to an increase in temperature caused by the ultrasound itself, a temperature of 20°C seems optimal when preparing the solution and filling the tank.

With my best regards

The properties of the liquid will also influence the effect of ultrasound: vapor pressure, interfacial tension and viscosity. As with temperature, an increase in the vapor pressure of the liquid facilitates cavitation but reduces the pressures and temperatures reached in the bubble when it implodes.

Removing bacteria from any surface is surely possible with ultrasound with sufficient intensity, but it could be eventually difficult with ultrasonic bath, since it is very difficult to control the intensity in such device and intensities in such devices could be even too small to have sufficient effect in your case. Bacteria are normally creating a film on the surface, that is not easy to remove. Especially if it is a rough and biologic surface. Critical for the effect is the local intensity (W/mm²), frequency dependence could also exist, but is not very probably and difficult to check. In your case it could be useful or even necessary to use instead of simple ultrasonic bath an ultrasonic transducer with suitable sonotrode, that can generate locally much higher sound intensity in a controlled way.

Values declared by bath manufacturers (Watts per gallon or similar) are misleading, since sound fields in ultrasonic baths are complicated and local differences large.