Techno-economic evaluation of simultaneous arsenic and fluoride removal from synthetic groundwater by electrocoagulation process: optimization through response surface methodology

Abstract

In the present work, electrocoagulation process has been used to treat arsenic and fluoride containing synthetic water using aluminium electrode. Box–Behnken design, a subnet of response surface methodology, was employed to fix the experimental conditions and Design Expert software was used to evaluate the interaction and effects of different process parameters such as initial pH, current density and run time on removal of arsenic and fluoride as well as the operating cost. Initial concentration of arsenic and fluoride was fixed at 550 μg/l and 12 mg/l, respectively, for all the experiments. High R2 values of three responses (arsenic removal: 0.998, fluoride removal: 0.984 and operating cost: 0.996) ensures a satisfactory adjustment of developed quadratic model with the experimental data. Under the optimum conditions, initial pH: 7, current density: 10 A/m2 and run time: 95 min, the predicted arsenic and fluoride removal is found to be 98.64 and 84.80%, respectively, whereas the operating cost is found to be 0.354 USD/m3. Further, the experimental values of arsenic removal (98.51%), fluoride removal (88.33%) and operating cost (0.343 USD/m3) are found to be in good agreement with the predicted values. The present electrocoagulation process is able to reduce the arsenic and fluoride concentration below 10 μg/l and 1.5 mg/l, respectively, which are maximum contaminant level of these elements in drinking water according to WHO. EDX analysis of sludge confirms the occurrence of arsenic and fluoride in produced sludge and FTIR spectra suggest that arsenic is also removed in the form of As(III). Real groundwater sample collected from Kaudikasa Village, Rajnandgaon District, Chhattisgarh, India and having As: 512 μg/l, F: 6.3 mg/l was also treated under optimum conditions of the present study and the concentration of arsenic and fluoride became below WHO drinking water norms.