Treatment of Train Industry Oily Wastewater by Electrocoagulation with Hybrid Electrode Pairs and Different Electrode Connection Modes

In this study, treatability of oily wastewater from train industry part washing machine was investigated by electrocoagulation process with aluminum, iron and hybrid electrodes (eight different combinations) and different electrode connection modes (series and parallel) in a batch reactor. The removal efficiencies for chemical oxygen demand (COD), total organic carbon (TOC) and turbidity were evaluated and the effects of different operating parameters such as electrode type (eight combinations), initial pH (4-10), current density (25-150 A/m2 ), air injection flow (0-6 L/min), electrode surface area (210-630 cm2) and connection mode (monopolar parallel, monopolar series and bipolar series) were investigated. The optimum operating conditions were identified as Fe-Al-Fe-Al (anode-cathode-anode-cathode) hybrid electrodes, initial pH of 6, current density of 75 A/m2, air injection flow of 2 L/min, electrode surface area of 210 cm2 and monopolar series (MP-S) mode. Under optimum operation conditions, removal efficiencies for COD, TOC and turbidity at 5 min operating time were respectively obtained to be 94.5%, 79.5% and 98.5%. The optimum operation cost at MP-S connection mode and hybrid electrode type was calculated as 0.60 $/m3. Current results revealed that the best results in EC process for pollutant removal from oily wastewater of train part washing machine could be achieved with Fe-Al-Fe-Al electrode pairs in MP-S electrode connection mode.