A set of chemical treatment procedures designed to remove organic (and sometimes inorganic) materials in water and waste water by oxidation through reactions with hydroxyl radicals (·OH). Advanced oxidation processes (AOP) combine ozone (O3), ultraviolet (UV), hydrogen peroxide (H2O2), and/or catalyst to offer a powerful water treatment solution for the reduction (removal) of residual organic compounds as measured by COD, BOD or TOC. All AOPs are designed to produce hydroxyl radicals.