Removal of ecotoxicological matters from tannery wastewater using electrocoagulation reactor: modelling and optimization

This study investigated the possibilities of electrocoagulation reactor to reduce the colour, oil and grease and chemical oxygen demand (COD) from tannery industry wastewater using stainless steel electrodes. Effects of pH, electrolysis time, current density and NaCl dose were investigated using four factors three-level Box–Behnken response surface design coupled with response surface methodology. From the experimental results, second-order polynomial mathematical models were developed to describe the treatment process statistically. Analysis of variance was used to evaluate the adequacy of developed mathematical models. Three-dimensional (3D) response surface plots were constructed to study the interactive effects of process variables on the treatment efficiency. Optimum operating conditions such as pH of 9, electrolysis time of 40 min, current density 20 mAcm−2 and sodium chloride (NaCl) dose of 1,016 mg l−1 show 92, 95 and 80% of colour, oil and grease, and COD removal, respectively. The electrical energy consumption of the present treatment process in optimum condition was found to be 6 KWhm−3. The obtained results indicate that EC reactor is the best option to treat tannery industry wastewater in terms of removal efficiency and operating cost.