Olive mill wastewaters (OMW) characterized by their dark brown colour and their very high content of phenolic compounds constitute an environmental concern, particularly in Mediterranean countries where the production of olive oil is important. In this investigation, OMW were electrolyzed at platinized expanded titanium electrodes in a modified Grignard reactor divided into two cylindrical compartments separated by a cation-exchange membrane. Results show better than 90% decolourization and nearly 85% removal of phenols, as established by gas chromatography/mass spectrometry, at high current intensity. This process can easily be monitored by cyclic voltammetry at a boron-doped diamond electrode. A significant reduction of chemical oxygen demand and total organic carbon was observed. The electrodes are not passivated and the ohmic potential drop is very low. Electrochemical oxidation in a modified Grignard reactor is a promising process for the destruction of phenolic compounds present in OMW.

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ab s t r ac tA recently developed anionic membrane has been found to be highly efficient for electrodialysis, a process commonly used to remove ions from aqueous solution. Nitrate ions are often present in too a high concentration in wastewater, therefore we investigated this electrodialysis system for their removal from aqueous solution. The good selectivity of the membrane for nitrate anions is shown by acid-base and spectrophotometric measurements, and also by comparison with the removal of acetate anions. This membrane itself is easy to prepare, shows good characteristics and could fi nd applications in large electrodialysis units.

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