Detergent waste can be treated by using chitosan as a coagulant to reduce its turbidity, phosphate levels and anionic surfactant levels. In this research, chitosan was dissolved in two different solvents, i.e hydrochloric acid (HCl) dan acetic acid (CH₃COOH) to study which solution works as a better solvent for chitosan to be used as coagulant. This treatment of detergent waste treatment was carried out through a coagulation-flocculation process using a jar test device. The optimum dose chitosan of and pH were investigated for both chitosan-acetate and chitosan-HCl. The results showed that the optimal dose for chitosan-acetate was 10 mg/L and 5 mg/L for chitosan-HCl. The decrease in turbidity, phosphate levels, and anionic surfactant levels for chitosan-acetate were 92.25%, 86.87%, 78.16%, respectively. As for chitosan-HCl, the turbidity, phosphate and anionic surfactant level were decreased by 88.78%, 86.39%, 77.96%, respectively. A pH value of 6 is the optimal pH value for both chitosan-acetate and chitosan-HCl in treating detergent waste. At this optimum pH, the decrease in turbidity, phosphate levels, and anionic surfactant levels for chitosan-acetate were by 89.63%, 89.71%, 78.41%, respectively. Coagulation using chitosan-HCl at this optimum pH decreased turbidity, phosphate levels and anionic surfactant levels by 91.56%, 92.79%, and 85.51%, respectively.

Keywords: Coagulation, chitosan, detergent waste, flocculation