The aim of the study was to investigate the efficiency of iron chloride in term of color, chemical oxygen demand (COD), TSS and turbidity removal of dye waste. Response surface methodology (RSM) using central composite design (CCD) was employed to analyze and investigate the effects of the independent factors on color, COD, turbidity, and TSS removal as well as the effect on phytotoxicity concentration. The efficiency of the optimal sample removal for dye color, COD, turbidity, and TSS were 91.89%, 85.40%, 98.36%, and 98.66%, respectively was achieved at a fixed pH value (X1) of 4, iron chloride dosage (X2) of 2.72 g/L, mixing time (X3) of 3 min and mixing speed (X4) of 30 rpm. While the phytotoxicity concentration was 53.05% at the optimal run which considered as not harmful and could be used for irrigation. The finding indicated that the use of iron chloride in coagulation-flocculation has high potential for treatment of dye waste.
