The processes of advanced chemical oxidation are applied to produce the oxidation of the organic complex constituents (which are difficultly biodegradable by biological way), transforming them into simpler final products. Often it is not necessary to oxidize completely a specific compound or a group of compounds, but, in many cases, it is sufficient only a partial oxidation of them, in order to make them less toxic or more easily degradable by biological treatment.
Generally, these processes involve the generation and use of free hydroxyl radicals (OH°) as strong oxidants for the destruction of compounds which cannot be oxidized by conventional oxidizing agents, such as oxygen, ozone and chlorine. The OX system is based just on this process and, by means of electrochemical oxidation, it allows to reduce the concentration of COD and color from a water that has a certain salinity.
The cells of the system are made of surfaces covered by a thin layer of diamonds (anode) and stainless steel surfaces which act as the cathode. Applying a current at low voltage and intensity, in the presence of soluble salts, such as chlorides and sulphates, you obtain the production of hydroxyl radical OH°. In this way, it is possible not only to break the double chemical links of molecules (even very complex, such as those of the dye, like benzene rings linked together), but also to destroy the benzene rings through their decomposition. Thus, you obtain smaller and more soluble compounds. These new simplified molecules can be sent to the biological treatment to be easily metabolized by enzymes and bacteria.
The life of the radical lasts some fractions of a second, so it is essential that its production takes place simultaneously with the passage of the liquid to be treated. The concentration of produced radicals can be regulated through a plating rectifier, which acts on energy supplied to the cell, according to the characteristics of the effluent to be oxidized.
A second very important parameter for the process is the contact time of the solution in the reactor. Increasing the duration of treatment (15, 30, 45 min.) you can reach different degrees of oxidation. Depending on the requirements, it is therefore possible to stop at an intermediate stage, reducing only in part the color or creating a biodegradable residue (which must be eliminated by a biological process), or obtaining a total reaction of transformation of the organic molecule, with production of water, CO2 and NO3-, and the disappearance of color and organic carbon (TOC).
The oxidation with an electrode covered with diamond increases the efficiency of the reaction and reduces the cost of the applied power. This solution finds its best applications as:
his technology is used as an integral part of the treatment process in a Partial Recovery Plant, or Zero Liquid Discharge Plant.