Pretreatment of Diosgenin Wastewater Using Polyferric Sulfate and Cationic Polyacrylamide

Coagulation-flocculation process was applied in the pretreatment of diosgenin wastewater.Polyferric sulfate was used as primary coagulant and a cationic polyacrylamide （CPAM） was used as coagulant aid.Using jar test procedure,the influence of the main operating parameters,such as effluent pH and coagulant dosage in the coagulation performance was investigated.The effective pH was found to be in the range of 6.5-8.0 and coagulant dosage was 100 mg/L.Under the optimal conditions,15% chemical oxygen demand （COD） removal efficiency was achieved and the residual turbidity was less than 20 NTU.The presence of CPAM substantially promoted the reduction of residual turbidity with the appropriate CPAM dosage in the range of 2-5 mg/L.