Optimization of Tobacco Leaf Thinnings Wastewater Flocculation Pretreatment Process Based on Response Surface Methodology

Using cationic polyacrylamide (CPAM) as a coagulant aid and polymeric ferric sulfate (PFS) as a flocculant, a PFS-CPAM composite coagulant was prepared to investigate the influence of single factors such as wastewater temperature, pH value, types and dosages of flocculants and coagulant aids on the flocculation process of wastewater. Based on the Box-Behnken experimental design principle, the Design-Expert 10.0 software was employed to establish a quadratic response surface numerical model for COD removal rate. Analysis of the model revealed that the highest CODcr removal rate, at 64.13%, was achieved when the pH was 6.8, with a PFS dosage of 485.5 mg/L and a CPAM dosage of 4.8 mg/L. Verification test results showed that the deviation was 0.23%, indicating a good agreement between the predicted values obtained by the response surface methodology and the actual values. This method is an effective approach for optimizing the flocculation pretreatment of wafer wastewater.