Hydrogen peroxide (H2O2) is rarely used in drinking water treatment as a stand-alone treatment process. H2O2 is a weak mirobiocide compared to chlorine, ozone, and other commonly used disinfectants. Consequently, it is not approved by regulatory agencies as a stand-alone disinfection treatment process. However, there are a number of technologies where H2O2 is used as part of the treatment program. The advanced oxidation process (AOP) uses H2O2 in conjunction of O3 and/or UV light to produce hydroxyl radicals (·OH), which are very effective in removing taste and odor (T&O) compounds, and inorganic and organic micropollutants. H2O2 can also be catalyzed with iron, to produce hydroxyl radicals by Fenton's reaction.
Addition of H2O2 in conjunction of UV light and/or ozone produces powerful hydroxyl radicals, which are more effective than ozone or UV alone. AOP involving hydroxyl radicals in drinking water treatment is used to remove various persistent organic and inorganic micro-pollutants. O3/ H2O2 and UV/ H2O2 have been successfully used to oxidize many persistent pesticides, T&O compounds, pharmaceutical and hazardous chemicals that may be present in surface and groundwater.
In the Fenton process, H2O2 and iron generate hydroxyl radicals through a catalytic process. The process is based on electron transfer between H2O2 and iron ions. The hydroxyl radical produced during this activation process is a strong oxidizing agent able to oxidize organic compounds. The advantage of this process is that no energy input is necessary to activate the hydrogen peroxide. However, the main disadvantage of this process is the additional water pollution caused by adding the iron salt. Solid iron blocks have been used to avoid water pollution with iron salt; however, leaching of metal ions makes this process problematic. Fenton's Reagent has proven to be very effective in the treatment of organic molecules. However, the process is expensive because additional residuals, which require disposal, are generated and a continuous supply of feed chemicals is required.