Treatment of CNC industry wastewater by electrocoagulation technology: an application through response surface methodology

Removal of COD, and several toxic heavy metals (Cu2+ and Ni2+) from CNC (metalworking fluid) wastewater was investigated using electrocoagulation method (EC) with Fe and Al electrodes. The interaction effects of the current density, reaction time and initial pH were analyzed and were correlated to assess the removal efficiencies for COD, copper, and nickel. Coefficient of determination (R2) and adjusted R2 was found to be higher than 96.81% and 92.77; 99.01% and 89.94 for all responses at Fe and Al electrodes, respectively. Removal efficiencies were determined to be 95.72%, 96.03%, 95.22% and 97.11%, 98.51%, 92.49% for COD, copper and nickel at iron and aluminum electrodes, respectively under optimum operating conditions. The operational cost of the EC process for COD, copper, and nickel removal, were found to be 2.54, 3.36, 2.50 €/m3 for iron electrode and 7.16, 8.95, 8.50 €/m3 for aluminum electrode at optimum conditions, respectively. The results provide that The EC process seems to be an effective treatment method for removing COD and several trace heavy metals from the CNC machine (metalworking fluid) wastewater.