reported that the charge density and molecular weight of polyelectrolyte play important role in the coagulation. Effluent COD and COD removal efficiencies versus different polyelectrolyte dosages are given in Figure 3. At the lowest concentration of polyelectrolyte, COD removal efficiency was 74% and effluent COD concentration was 6.4 g/L . With increase in polyelectrolyte concentration, removal efficiency increased up to 87%. At a higher concentration than 50 mg/L, effluent COD decreased thus 50 mg/L polyelectrolyte dosage was accepted as optimum dosage. Optimum concentration of polyelectrolyte forms a bridge between particles and cause good flocculation. However high concentration of polyelectrolyte forms an envelope on the suspending particles and causes them to remain in suspension thus removal efficiency decreases [18]. Similar result was obtained from this study and when the polyelectrolyte concentration was increased, process performance was decreased.