Fig. 1 shows the removal of turbidity using flocculant doses ranging from 0 to 50 mg/L, for three sedimentation times (10, 20 and 30 min). The concentration of the coagulant added was 0.025 mM Al3+. An increase in flocculant dose up to 20 mg/L resulted in gradually increasing turbidity removal. The optimum turbidity removal at 20 and 30 min sedimentation time was achieved with 12 mg/L of flocculant. At 10 min sedimentation time, 20 mg/L of flocculant were required. At the optimum doses, turbidity was reduced by 96.3–97.4%, at all sedimentation times. This is an additional 28, 7 and 9 removal percentage points compared to aluminum sulfate alone, at 10, 20 and 30 min settling time, respectively. Therefore, the sedimentation time of 20 min and the dose of 12 mg/L were selected as the optimum combination of the lowest time and dosage for the highest turbidity removal. Beyond the optimum flocculant dose, a slight decreasing trend was observed, where the turbidity removal was reduced to 81–96%. The reason for this was the restabilization of the solution as the flocculant dose was increased. This behavior (increasing and then decreasing trend) can be explained by the fact that the optimum amount of flocculant in the suspension caused the maximum amount of particles to aggregate and settle. Beyond the optimum dose, steric stabilization of the particles took place, thus increasing turbidity.