Significance of hybrid central composite design for remediation of paper mill wastewater through electrocoagulation

Department of Chemical Engineering, National Institute of Technology Raipur, Raipur-492 010, Chhattisgarh, India E-mail: cthakur.che@nitrr.ac.in Manuscript received online 20 April 2020, accepted 12 June 2020 In the present study, hybrid central composite design (HCCD) was chosen to optimize four variables based remediation of paper mill wastewater by using electrocoagulation (EC). Response surface methodology incorporates with HCCD designs are rarely used by researchers for optimization of paper mill wastewater remediation. pH, electrode distance, conductivity and current density are operating variables which were selected for optimization over response parameters like COD, color and TDS. EC experiments were performed in 1.5 L capacity reactor with four aluminum electrodes connected to DC power supply. 35 min of electrolysis time for remediation of paper mill wastewater was determined by performing EC experiments with respect to time. Quadratic model was suggested by HCCD design for 20 sets of experimental runs. The signification of this design was measured in terms of regression analysis and t-test. For all response variables regression coefficient and p-value are > 0.80 and < 0.05 respectively. Desirable solution for optimization is obtained at pH = 7.11, electrode distance = 1.98 cm, conductivity = 7.07 mS/cm and current density = 13.76 mA/cm2. Reduction in COD, color and TDS were 80.89%, 93.37%, and 87.54% respectively.