ABSTRACT
In spite of the relatively small concentrations, the residues of pharmaceuticals and personal care products in wastewater are a concern, mainly because of their resistance to degradation in conventional wastewater treatment plants. The advanced oxidation process (AOP) that relies on free radicals with very high oxidation potential is a promising technology for tackling these recalcitrant pollutants. A major challenge in the application of the technology is the requirement to generate these free radicals within the treatment system because of their highly unstable nature and extremely short life span. Among the various oxidant radicals, the •OH radical is the one most commonly generated in aqueous systems. Consequently, most AOP systems rely on •OH radicals for oxidation. The classification of AOP systems is based on the method adopted for the generation of free radicals. Some AOP systems use chemical reagents for the generation of free radicals, whereas the others use some form of energy (radiation, light, sound, electricity, etc.). But, most systems use a combination: Fenton-based systems, ozone-based systems, electrochemical systems, radiation-based systems, sonolysis-based systems, and photolysis-based systems, all frequently researched, are explained in the chapter along with the governing chemical equations.
