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Optimization of electrocoagulation process for treatment of rice grain-based biodigester distillery effluent using surface response methodology approach

Abstract Distillery industries are the most water-consuming industries discharging a large amount of wastewater that contain a high organic load. Hence it is first treated in biodigester where significant organics reduces (50–60%) and the outcome of biodigester is commonly known as biodigester effluent (BDE). The present study is an attempt to treat BDE in terms of COD and color removal using a batch electrocoagulation reactor (ECR) where stainless steel (SS) is used as an electrode. To optimize the four independent parameters namely initial pH (pHi: 3.5–9.5), current density (j: 49.5–247 A/m2), electrode gap (g: 1.2–3.2 cm), and reaction time (t: 20–100 min) on the color and COD reduction efficiency, a central composite design (CCD) experiment is applied to evaluate the individual and interactive effects of these parameters. The high coefficients of determination for color (R2 = 0.9989) and COD (R2 = 0.9981) were obtained by analysis of variance (ANOVA) between the experimental data and the predicted data using a second-order regression model. At the optimum condition color and COD removal of 81.4 and 91.9%, respectively, were observed. A material balance of SS has also been incorporated.