Video Upload Options

Advanced oxidation processes are water-treatment methods that destroy organic contaminants through the action of strongly oxidising radical species, hydroxyl and sulfate radicals above all, generated in situ rather than dosed. Because the radicals react rapidly and with little selectivity, these processes come into their own where biological treatment fails, on compounds that are toxic, refractory or present at low concentration; the target is mineralisation, or at least conversion into intermediates that a biological step can then remove ^[1]. The classical route is the Fenton reaction, in which iron activates hydrogen peroxide; variants invoke ozone, ultraviolet light, semiconductor photocatalysis or electrochemical generation, and the choice depends on the water matrix, since carbonate and natural organic matter scavenge the radicals and raise the dose required ^[2]. Coupling one process with another, or with a biological or membrane stage, is generally more efficient than any single treatment, which is why integration is now the main direction of development ^[3]. Heterogeneous catalysts avoid the sludge produced by dissolved iron, and perovskite oxides activate peroxides at near-neutral pH ^[4]; iron oxide minerals catalyse the same chemistry without added iron ^[5]. Energy demand and the formation of oxidation by-products remain the main objections.