The Treatment of Actual Industrial Wastewaters Using Electrochemical Techniques

The electrochemical oxidation of an actual waste which comes from a chemical plant was studied. This effluent is generated in a polymerization unit and is mainly composed of a great variety of organics (including a complex mixture of water-soluble polymers of very different molecular weights) and solvents. The high variability of the organic load in industrial waste stream (4,000-20,000 mg dm(-3) of chemical oxygen demand (COD)) makes the study of the system difficult. The results show that the key for an efficient electrolytic treatment is the selection of the anode material. The replacement of dimensional stable anodes by non-active electrodes is technically feasible as it leads to a very efficient process in terms of COD and total organic carbon removal. However, the use of PbO2 favours the release of toxic lead ions to the reaction medium. The efficiencies seem to depend on the pH and supporting electrolyte. This does not seem to be related to the electrochemical process, but to the oxidizability of the pollutant (mainly polymers) that should strongly depend on the pH. It is suspected that some functional groups of the polymer were more easily attacked by reagents electro generated under extreme pH values and that hypochlorite is less effective than persulphate. Regarding economic viability, electrochemical oxidation with a boron-doped diamond electrode can be used in an economically adequate way for the pretreatment of waste, but the energy cost necessary to deal with mass transfer limitations made this technique unsuitable for its use in a refining process of the quality of an effluent.