The chemical coagulation experiments were conducted with the jar test method. PFS was used as the coagulant. The operating variables were dosage of PFS and the pH. Every beaker was first filled with 1000 mL of wastewater sample, and the pH was adjusted to the designed value with 3 M NaOH or H2SO4. Then PFS were added and the coagulation experiments proceeded with rapid mixing of water samples at 300 rpm for 1 min, slow mixing at 50 rpm for 15 min and then standstill for 30 min. The supernatant was withdrawn for COD and color analyses.