Application of Response Surface Methodology (RSM) for optimizing removal of Cr(VI) wastewater using Cr(VI)-reducing biofilm systems

Abstract

Response surface methodology (RSM) involving central composite design (CCD) was employed to obtain optimal conditions for Cr(VI) wastewater treatment by Cr(VI) reducing biofilm systems. On the basis of a CCD, RSM was used to determine the effect of initial metal concentrations (40-100mg/L), nutrient supplementations (10-20%) and flowrate (3-6mL/min) on the levels of response, i.e. Cr(VI) reduction efficiency. A set of 20 experimental runs were needed for optimizing of the operating conditions. Quadratic regression models with estimated coefficients were developed to describe the Cr(VI) reduction. Analysis of variance (ANOVA) showed a high coefficient of determination (R2) value of 0.9941, thus ensuring a satisfactory adjustment of the second-order regression model with the experimental data. Cr(VI) reduction had significant effect on all the three dependent variables. The experimental results show that Cr(VI)-reducing biofilm systems could effectively reduce Cr(VI), 100% at the optimum conditions of initial metal concentration of 100 mg/L, nutrient supplementation of 20% and flowrate of 3mL/min. The experimental observations were in reasonable agreement with the modelled values.