Today there are increasing levels of environmental pollution, both chemical and biological. Sonochemistry has been found to greatly assist a range of advanced oxidation processes either alone, or combined with ozonation, Fenton’s processes, ultraviolet light with and without catalysts and with electrochemistry. Ultrasound offers the possibility of a green cost effective technology for the future in that, under the right conditions, it is capable of inactivating waterborne bacteria either alone or in combination with other technologies. Ultrasound induces acoustic cavitation in a medium and in turn this produces high shear forces and radical species both of which are harmful to bacteria.
The mechanical effects of cavitational collapse together with the production of radical species such as hydroxyl radicals (HOo) combine to provide the essential elements for both the biological and chemical decontamination of water. There is an increasing incidence in health problems related to environmental issues, which originate from inadequate treatment of potable waters. This has compelled scientists and engineers to engage in innovative technologies to achieve a maximum disinfection at affordable costs. Some species of bacteria produce colonies and spores, which agglomerate in spherical clusters and this protects organisms on the inside against biocidal attack. Flocs of fine particles e.g. clay can entrap bacteria which can also protect them against the biocides. Some bacteria have the ability to mutate thus building up resistance to conventional biocides (e.g. chlorine) but ultrasound can be used to improve the efficiency of such biocides.
Power ultrasound can be used for the rehabilitation of industrial sites or the reclamation of polluted land by the removal of chemical and biological contamination from soil. Two basic mechanisms for acoustically enhanced soil cleaning have been suggested (a) an increase in the abrasion of suspended soil in slurries leading to the removal of contaminated material from the surface of particles and (b) an improvement in the leaching of pollutant materials that are more deeply embedded.
Sonochemistry has also been applied successfully to enhance the treatment of sewage/sludge and more recently in the field of degrading biomass for the production of biofuels.