Optimization of operating parameters for aggregation under magnetic field by response surface methodology

Abstract

Batch tests were employed to estimate the optimal conditions for improving the settle ability of activated sludge through aggregation under magnetic field. A four - factor central composite design (CCD) was employed to find out the interaction effects of the variables while response surface methodology (RSM) was utilized for process optimization. Four independent variables, viz. magnetic field (15.0 - 88.0 mT), exposure time (0.5 - 48.0 hrs), biomass concentration (2000 - 4000 mg l-1 ) and mixing intensity (200 - 400 rpm) was built to predict the responses. Analysis of variance (ANOVA) was used to evaluate the significance of the independent variables and their interactions. At the optimum conditions of 88.0 mT magnetic field, 16.5 hrs of exposure time, 2800 mg l-1 of biomass concentration and 300 rpm of mixing intensity, the aggregation achieved its maximum value by 99.0%. The element analysis showed that the applied magnetic field is potential to enhance the settling property of the activated sludge by improving its aggregation.