Advanced oxidation processes (abbreviation: AOPs), in a broad sense, are a set of chemical treatment procedures designed to remove organic (and sometimes inorganic) materials in water and wastewater by oxidation through reactions with hydroxyl radicals (·OH). In real-world applications of wastewater treatment, however, this term usually refers more specifically to a subset of such chemical processes that employ ozone (O3), hydrogen peroxide (H2O2) and/or UV light.One such type of process is called in situ chemical oxidation. APPLICATIONs OF AOPs:- COD removal of complex / recalcitrant organic compounds presents in wastewaters Color and odor removal Post-treatment option for residual COD, toxicity and color reduction Sludge treatment such as enhancement of sludge dewatering capacity Pre-treatment option for BOD enhancement