Optimization of Coagulation Parameters for Turbidity Removal Using Box-Behnken model

Abstract

This study aims to determine the efficacy of using calcium hydroxide Ca(OH)2 in coagulation process to treat urban liquid effluent from wastewater purification plant. The response surface methodology was used. The effects and interactions between three key process parameters was enhanced applying Box-Behnken design. Factors studied were: coagulant dosage (g/L), coagulation speed (rpm), and coagulation time (min). The treatment efficiency was determined by the turbidity removal rate and the final pH of the treated wastewater. The statistical soundness of the generated model was determined using analysis of variance. The optimal model for determining the relationship between the variables is a second-order quadratic model (R2>98 %). The best turbidity reduction (91.3 %) was obtained using a 0.50 g/L Ca(OH)2 coagulant and 130.1 rpm for 5 minutes. Under these conditions, the ultimate pH of the effluent reached 8.