Decolourization and removal of phenolic compounds from olive mill wastewater by electrocoagulation

The effective performance of electrocoagulation (EC) technique in the treatment of olive mill wastewater (OMW) has been investigated using sacrificial aluminium electrodes. The optimum working pH was found to be in the range 4-6, allowing OMW to be treated directly without pH adjustment. In addition, it is found that an increase in the current enhanced the speed of the treatment significantly. However, simultaneous increase of electrode and energy consumption was observed. The optimum current density allowing the quickest treatment with a low cost was found to be 75 mA cm-2. Therefore, a current density of 75 mA cm-2 was selected as an optimum that allows fast and low cost treatment. Application of electrocoagulation procedure permitted high removal efficiencies of pollutants with both fresh and stored olive mill wastewater. The process produces a removal capacity of 76% of COD, 91% of polyphenols and 95% of dark colour, just after 25 min. The electrode consumption was found to be 2.11 kg m-3 of treated OMW. The results show that electrocoagulation could be considered as an effective alternative solution for the treatment of OMW or may be combined with a classical biological process to achieve a high quality effluent water. © 2004 Elsevier B.V. All rights reserved.