Toxicity reduction on pretreatment of traditional Chinese medicine wastewater by enhanced coagulation

A coagulation process was applied to the pretreatment of traditional Chinese medicine wastewater with high toxicity, SS, COD, and color. At first, the coagulation performances of PFS, PAC, AS, and FeSO₄ were compared, and PFS was chosen as the optimal coagulant for the reduction of acute toxicity and the removal of COD and SS. Then, the effect of initial pH and coagulant aids (PAM and Chitosan) on the coagulation performance of PFS was investigated to determine the optimal coagulation parameters. The optimal conditions for PFS dosage, PAM dosage, and initial pH were 500 mg·L^-1, 8 mg·L^-1, and 7.0 respectively; the removal efficiency of COD and SS were 38.6% and 98.9% respectively; and the acute toxicity was reduced from EC₅₀=8.12% to EC₅₀=41.35%.