Removal Of Pollutants From Domestic Wastewater Using Electro Oxidation Process: Optimization Through Response Surface Methodology

Abstract

The electrochemical oxidation of domestic effluent was studied in a batch reactor in the presence of supporting electrolyte NaCl, CaCl2 and Na2CO3 using stainless steel electrodes. The effect of operating parameters such as current ampere, pH, electrolysis time, inter-electrode distance and supporting electrolyte concentration on the percentage of color, COD, turbidity removal and power consumption were studied. The maximum percentage removal of color, COD and turbidity was 94.76%, 77.93% and 92.19% respectively at an initial pH of 8.99, current ampere of 0.18A, electrolysis time of 30 minutes, inter-electrode distance of 2cm and electrolyte concentration (i.e. NaCl) of 3gm/L for NaCl, the maximum percentage removal of color, COD and turbidity was 99.97%, 79.11% and 90.00% respectively at initial pH of 8.68, current ampere of 0.10A, electrolysis time of 30minute, inter-electrode distance of 2cm and electrolyte concentration (i.e. CaCl2) of 1gm/L for CaCl2 and the maximum percentage removal of color, COD and turbidity was 83.78%, 83.16% and 93.66% respectively at initial pH of 8.98, current ampere of 0.10A, electrolysis time of 30minute, inter-electrode distance of 1.99cm and electrolyte concentration (i.e. Na2CO3) of 2.40gm/L for Na2CO3. The operating parameters for the treatment of domestic effluent by electrochemical process were optimized using response surface methodology. The quadratic regression models with estimated coefficients were developed for the percentage removal of color, COD, turbidity and power consumption. It was observed that the model predictions matched with experimental values with an R2 values of 0.5889, 0.8695, 0.6218 and 0.5428 for color, COD, turbidity and power consumption respectively for NaCl, R2 values of color, COD, turbidity and power consumption for CaCl2 were 0.5987, 0.8574, 0.6945 and 0.6215 respectively and R2 values of color, COD, turbidity and power consumption for Na2CO3 were 0.6868, 0.8979, 0.6430 and 0.5771 respectively. The extent of color and turbidity removal were analysed using UV spectrophotometer and turbidity meter respectively. Besides, the operating costs investigated in the study were the energy cost of electro oxidation and the material cost because of consumption of stainless steel electrodes. Operating costs are 1.076$/m3 for NaCl, 1.077$/m3 for CaCL2 and 1.072$/m3 for Na2CO3 wastewater treatment.