6.2.6 Advanced oxidation processes
Advanced oxidation processes (AOP) facilitate the conversion of contaminants into into less toxic and more easily degradable substances by generating free radicals, specifically hydroxyl radicals (Ikehata et al., 2008).UV radiation is typically the first step in the production of hydroxyl radicals, which can be produced using a variety of techniques, including ozone (O3), hydrogen peroxide (H2O2), photolysis with ultraviolet light, homogeneous Fenton reagent, heterogeneous semiconductors, electrolysis with ultrasound (sonolysis), and microwave radiation (Gogoi et al., 2018; Pavithara and Jaikumar, 2019). Sichel et al. (2011), , using UV/chlorine advanced oxidation, degraded ECs such as 17α- ethinylestradiol, sulfamethoxazole, diclofenac, benzotriazole, carbamazepine, tolyltriazole, iopamidol, desethylatrazine and carbamazepine. AOPs based on ozone treatment have been shown to be effective in treating wastewater containing a variety of pharmaceuticals, including angiotensin II receptor antagonists, cocaine, its metabolite benzoylecgonine, anti- inflammatory medicines, cholesterol-lowering statins, and antibiotics (Ibannz et al. 2013). Research has demonstrated the efficacy of AOPs in degrading pharmaceutical compounds in water, either individually or in combination with other degradation methods—over 80% and up to 90%—when used with various processes namely coagulation, flocculation, nanofiltration, and electrocatalytic oxidation (Pavithra & Jaikumar, 2019; Rayaroth et al., 2016).