Response Surface Methodology Approach to Optimize Parameters for Coagulation Process Using Polyaluminum Chloride (PAC)

Coagulation is a process affected by multiple variables, nonlinear mapping and multiple perturbations. In order to realize the precise dosage of flocculants, polyaluminum chloride (PAC) was taken as the research object to explore the effects of temperature, water turbidity, pH and CODMn on the dosage of PAC and coagulation effect. A response surface methodology (RSM) experiment was carried out based on a single-factor experiment. The turbidity, pH and dosage of a single parameter, as well as the interaction term and secondary term, all have significant influence on coagulation effect. The optimal reaction conditions were calculated using Design-Expert software: pH, 7.48; turbidity, 14.59 NTU; dosage, 24.01 mg/L; and the error between the experimental value and the predicted value, 4.08%. Establishing a model with residual turbidity as a consideration index can help to calculate the optimal dosage of PAC, which is conducive to a reasonable and accurate control of the dosage of PAC in the coagulation process, so as to achieve the goal of low turbidity of effluent and low production cost.