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Optimization of the Coagulation-flocculation Process for Wastewater Treatment Using Polymeric Ferric Sulfate (PFS) - Poly-diallyldimethyl Ammonium Chloride (PDADMAC) Composite Coagulant

Abstract

Huaili Zheng, Tiroyaone Tshukudu and Jun Yang

In this study, coagulation-flocculation process was optimized using PFS, PFPD₁, PFPD₂ and PFPD₃. The response surface methodology was used to investigate the effect changes in the level of coagulant dose and coagulation pH have on turbidity and COD removal. In addition, the optimum combination of coagulant dosage and coagulation pH that yields the maximum removal of turbidity, and COD were determined. The results revealed that the optimum conditions for the four coagulants were dosage of 388 mg/L and pH of 7.6 for PFS; dosage of 388 mg/L and pH of 7.45 for PFPD₁; dosage of 351 mg/L and pH of 8.0 for PFPD₂; dosage of 419 mg/L and pH of 7.64 for PFPD₃. The model showed that for turbidity removal, the effectiveness of the coagulants in decreasing order was PFS>PFPD₁>PFPD₂>PFPD₃ while for COD removal, the order was PFPD₂>PFPD₃>PFS>PFPD₁. The verification experiments demonstrated a good agreement between experimental data and model values. Therefore, the RSM approach was appropriate for optimizing the coagulation-flocculation process.