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206   Industrial Wastewater Treatment, Recycling, and Reuse


             The results obtained during the trials clearly show that during the process
          both COD and TOC are reduced. It was also seen that the consumption of
          peroxide is lower than that predicted from stoichiometric data.



          4.6 ELECTROCHEMICAL ADVANCED OXIDATION
          TREATMENT WITH BDD

          Unlike Fenton-based AOP, where oxidants are generated using external
          chemicals, the electro-oxidation process generates these oxidants in situ
          using a nonsacrificial electrode set (electrochemical reactor). These nonsa-
          crificial electrodes are selected based on their capacity to generate hydroxyl
          radicals and other secondary oxidants such as chlorine. Principal advantages
          of this technology are:
          1. It is a zero sludge process, i.e., during the process of oxidation no sludge
             is formed.
          2. It can work as a standalone treatment process for wastewaters that are
             very difficult to treat because it requires no chemical input and generates
             no sludge.
          3. Unlike the Fenton process, oxidation of organics in electro-oxidation
             can be selective or unselective depending on the oxidant that is generated
             in the electrochemical cell.
          However,
          1. Electro-oxidation is a capital intensive process when compared to the
             Fenton family of processes.
          2. Because different electrodes have varying capacities for generation
             of oxidants, the selection of electrode is critical for an efficient
             electro-oxidation process.
          In recent years, electrochemical oxidation with conductive-diamond anodes
          has appeared as one of the most promising technologies in the treatment of
          industrial wastes polluted with organics. Compared with other electrode
          materials, conductive-diamond has shown a higher stability and efficiency.
          During recent years, conductive-diamond electrochemical oxidation has
          been widely studied with synthetic industrial wastes in lab- and bench-scale
          plants (Can ˜izares et al., 2006a).
             Recently, it has been demonstrated that hydroxyl radicals are formed
          during the electrolysis of aqueous electrolytes on conductive-diamond
          anodes (Aquino et al., 2012; Can ˜izares et al., 2006b). This has enabled clas-
          sification of this technology as an AOP. Besides this mechanism, the global
          oxidation process in conductive diamond anodes is complemented by direct
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