Treatment of oil tanning effluent by electrocoagulation: Influence of ultrasound and hybrid electrode on COD removal

An electrocoagulation (EC) laboratory scale system was studied for the removal of COD in effluent from an oil tanning industry. The influence of operating parameters such as nature of electrolyte, current density, initial COD concentration and electrolyte concentration were analyzed on the percentage COD removal along with power consumption for the treatment. Amount of sludge produced was quantified after each process. Iron (Fe) and aluminium (Al) electrodes were considered as sacrificial electrodes in different combinations. Under optimal operating conditions such as 20 mA/cm2 current density, 5% effluent concentration, 1 g/l NaCl concentration and Fe/Fe electrodes, % COD removal, energy consumption and operating cost were found to be 89.65%, 1.279 kW h/m3 and 6.28 US $/m3 respectively. EC was better than sono-electrocoagulation for the treatment, however it was found that impingement of ultrasound can be used to overcome passivation. Non-linear mathematical model has been developed for COD removal using the experimental values with r2 value 99.7 and found to project the COD removal for undiluted raw effluent with 94.44% accuracy.