TREATMENT OF COMPLEX SYSTEMS ADVANCED OXIDATION PROCESSES

Many water streams, both wastewater effluents and drinking8 water sources, contain pollutants that cannot be removed or destroyed by conventional physical or biological treatment processes. In such cases it is necessary to seek alternatives. One approach is to destroy the pollutant by application of a strong oxidizing agent. Chlorine is one candidate reagent, but it can produce undesirable reaction products, and residual chlorine can be toxic to aquatic life. Ozone is also used, but it is expensive, and its low solubility in water limits process efficiency. Another category of oxidation processes has been developed in recent years based on the oxidizing strength of hydroxyl radicals. Other processes that involve electrochemical treatment or ultraviolet radiation have received attention. This chapter describes some of these processes, particularly those using peroxide and catalyzed by iron ions in the so-called Fenton reaction (Fenton 1894). Modifications and enhancements of the Fenton process include combinations with UV radiation, semiconductor catalysts, and electrolysis. It has been found that such combinations are necessary and appropriate in order to achieve satisfactory water purification.