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Electrocoagulation vs Electro-oxidation

An Introduction


In the electrocoagulation process, electrodes (anode and cathode) are suspended in a reaction chamber containing wastewater and direct current is passed through them. During the process, the anode (iron or aluminium) is oxidized to ferrous or aluminium ions.

At cathode, water molecules are lysed to protons (H+) and hydroxyl ions (OH). The generated protons are reduced to hydrogen gas and hydroxyl ions which combine with the aforementioned metal ions to produce metal hydroxide flocs. These flocs are primarily responsible for contaminant removal and are settled along with the contaminants, leaving clean supernatant to be then discharged as treated effluent.

Figure 1: Mechanism of Electrocoagulation

Figure 2: Electrocoagulation Reactor



Electrochemical advanced oxidation process (EAOP) is a new type of electrochemical oxidation. The electrochemical oxidation process involves the application of an external source of energy into an electrochemical cell that contains one or more pairs of electrodes. At the cathode, a reduction reaction occurs, and the oxidation reaction takes place at the anode.

EAOP can eliminate contaminants at the interface of the anode/aqueous solution (direct oxidation), and via anodically generated intermediates e.g. reactive oxygen species like hydroxyl radicals (HO•) and active chlorine species (indirect oxidation). Hydroxyl radicals are highly reactive oxidants that can react with nearly all organic contaminants and eventually mineralize them to CO2 and H2O non-selectively in ambient pressure and atmospheric temperature.

Figure 3: Mechanism of Electro-oxidation

Figure 4: Electro-oxidation Reactor



Broadly, electrochemistry offers

– highly efficient removal of dissolved metals, dyes, silica, and recalcitrant organics

– highly automated O&M, reducing operational complexity

– robust process, meaning reliability and less monitoring

– reduction/elimination of chemicals usage

– reduction/elimination of sludge

– reduced treatment time 

– cost-effective wastewater treatment solution

Electrocoagulation, on one hand, is a relatively quick process and very effective in removing colloidal and suspended particles, as seen in changes in coliforms, turbidity, and color. On the other hand, Electrooxidation excels in breaking down persistent or refractory organic compounds through direct oxidation (HO•) and indirect oxidation (chlorine and hypochlorite). Additionally, Electrooxidation does not require additives e.g. chemicals or oxygen.


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