Effective process conditions and reactor design parameters for oil separation by electrocoagulation

Abstract

Thermal power generating plants, service stations and oil refineries generate oily wastewaters which are recognized to be a severe threat to aquatic environments. Electrocoagulation has received considerable attention lately as a clean technology option yet absence of reactor design criteria and scientific understanding of the complex phenomena involved remain as a drawback to its widespread application. Laboratory experiments were conducted to determine the optimum operating parameters such as electrode type, influent pH, initial oil concentration, electrode polarity change, electrode surface area: reactor volume, current density and electrode spacing on COD removal efficiency. The effective pH for oil removal is dependent on the anode material used. A pH of 4 is suitable when A1 is used where as the effect of pH is negligible for iron electrodes. High removal efficiencies are obtained for moderate oil concentrations of 400-500mg/l as COD. The optimum current density and electrode surface area to volume ratio were 46.9 A/m2 and 8.5 m2/m3 respectively. The electrode polarity switch leads to rapid dissolution of the electrodes and improved COD removal efficiency. The developed design parameters enable the design of low cost compact treatment units that could be powered by DC sources for effective oil separation from wastewaters.