Combined Application of Ultrasound with Ozone

Advanced oxidation processes (AOPs) are a range of water treatments which involve the in situ formation of radicals, particularly hydroxyl radicals, in sufficient quantity to affect chemical or biological contaminants. These include ultrasonic and ultraviolet irradiation but they are sometimes ineffective for the remediation of water which contains a mixture of organic and inorganic compounds. Chemical oxidants can be used to add additional oxidising power to such processes and ozone in conjunction with ultrasound is one such option [31]. 

Ozone (O3) is a very strong oxidant which can oxidise organic compounds to carbon dioxide and water but the reaction rates for many pollutants are slow. Nevertheless ozone has been used at water and wastewater treatment plants in a variety of applications [32]. 

The combination of sonication and ozonation provides three sources of OH [33]  

from the thermolytic decomposition of ozone in the acoustic cavitation bubble. 

Studies of the combined process involving ultrasound and ozone have shown faster degradation rates for a range of chemical contaminants than either method applied alone. Sonolytic ozonation has also been found effective for the disinfection of water but in these cases sonication also has a number of direct effects on the bacteria and viruses (see above). 

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