The main driving mechanism in the degradation of pollutants using ultrasound is the generation and subsequent attack of the free radicals.
In the case of reactions where the controlling mechanism is the free radical attack, use of H2O2 or O3 in combination with the ultrasound should enhance the rates of degradation due to the generation of additional free radicals.
It can be said that the use of H2O2 in conjunction with ultrasound is beneficial only till an optimum loading of the oxidant and where the free radical attack is important.
The synergistic effect of combining ozonation with ultrasonic irradiation is observed only when the free radical attack is the controlling mechanism.
The rate of sonolytic ozonation will be higher at lower concentration of the pollutant and hence the dilution of effluent stream may be considered as a pre-treatment step.