Degradation and biodegradability improvement of the olive mill wastewater by peroxi-electrocoagulation/electrooxidation-electroflotation process with bipolar aluminum electrodes

Esfandyari, Yahya; Mahdavi, Yousef; Seyedsalehi, Mahdi; Hoseini, Mohammad; Safari, Gholam Hossein; Ghozikali, Mohammad Ghanbari; Kamani, Hossein; Jaafari, Jalil

Degradation and biodegradability improvement of the olive mill wastewater by peroxi-electrocoagulation/electrooxidation-electroflotation process with bipolar aluminum electrodes

2015

Olive mill wastewater is considered as one of the most polluting effluents of the food industry and constitutes a source of important environmental problems. In this study, the removal of pollutants (chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), polyphenols, turbidity, color, total suspended solids (TSS), and oil and grease) from olive oil mill processing wastewater by peroxi-electrocoagulation/electrooxidation-electroflotation process with bipolar aluminum electrodes was evaluated using a pilot continuous reactor. In the electrochemical unit, aluminum (Al), stainless steel, and RuO₂/Ti plates were used. The effects of pH, hydrogen peroxide doses, current density, NaCl concentrations, and reaction times were studied. Under optimal conditions of pH 4, current density of 40 mA/m², 1000 mg/L H₂O₂, 1 g/L NaCl, and 30-min reaction time, the peroxi-electrochemical method yielded very effective removal of organic pollution from the olive mill wastewater diluted four times. The treatment process reduced COD by 96 %, BOD₅by 93.6 %, total, polyphenols by 94.4 %, color by 91.4 %, turbidity by 88.7, suspended solids by 97 % and oil and grease by 97.1 %. The biodegradability index (BOD₅/COD) increased from 0.29 to 0.46. Therefore, the peroxi-electrocoagulation/electrooxidation-electroflotation process is considered as an effective and feasible process for pre-treating olive mill wastewater, making possible a post-treatment of the effluent in a biological system.

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