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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