Electrochemical treatment of oily wastewater using three dimensional steel wire electrodes

Electrochemical technologies have been successfully applied for the removal of heavy metals, dyes, organics and oils from wastewater. In this study, the treatment of synthetic oily wastewaters prepared from 2% by volume of bor oil (Petrol Ofisi) was carried out by using steel wires (SS410) as electrodes. In the experiments, the beds made of strip steel wires with a width of 0.65 mm were used as anode and cathode electrodes. The potential difference of 5, 10 and 15 V was applied to the electrodes and the highest oil removal (90%) was obtained with the highest potential difference applied. It has also been observed that the oil removal efficiencies obtained with steel wire bed electrodes were higher than those obtained with the use of steel plate electrodes. Experiments were also carried out with constant potential difference (15 V) for three different electrode bed lengths (9, 18 and 27 cm) since it is known that the current density is a significant influence on the removal efficiency of the electrochemical treatment. When the electrode bed length was 9 cm, the removal efficiency was low (87%) and 90% oil removal efficiencies were obtained at 18 cm and 27 cm lengths. However, the corresponding specific energy consumption ABSTRACT (continued) for these two bed lengths were calculated as 5.62 kWsa/m3 and 9.10 kWsa/m3 were obtained. When the removal efficiency and energy consumption were analyzed together, it was determined that the optimal electrode bed length was 18 cm. In addition, three materials which were made of polyurethane having different porosities and conductivities were placed in between the electrode beds and were tested for the use of insulating materials. Depending on the conductivities of the materials, it has been observed that the oil removal efficiencies can vary between 10% and 90%. Electrochemical treatment experiments were performed at three different volumetric flowrates (51, 108, 146 mL/min) in batch and continuous flow, with the potential difference applied the electrodes keeping constant at 15 V. In the batch flow, the treated water was continuously recycled to the entrance. Therefore, approximately the same oil removal efficiency was obtained for the three studied flowrates and was around 90%. The corresponding steady state removal efficiencies at the studied volumetric flowrates were 89%, 78% and 55%, respectively, in the continuous flow operation. In the final stage of the study, the electrochemical treatment experiments at batch flow were carried out using bilge water diluted to 5% by volume and 90% oil removal efficiency was obtained.