This study aimed to eliminate algae from waste stabilization ponds effluent, using chitosan through coagulation-flocculation-sedimentation process. The primary criterion to evaluate the efficiency of chitosan usage was turbidity removal. Therefore, the samples of waste stabilization pond effluent were tested using chitosan, poly aluminum chloride and ferric chloride, and the results were compared together. Also, COD and coliform removal were measured in some samples coagulated using chitosan. All the tests were held in three pH levels of 5, 7.5 and natural pH. The tests were done in coagulant dose levels of 20, 40, 60, 80 mg/L for chitosan, 50, 100, 150 mg/L for poly aluminum chloride and 100, 150 and 200 mg/L for ferric chloride. Chitosan has a suitable function of turbidity removal, making denser and more settleable flocs. The highest turbidity removal efficiency of chitosan is 91% in basic pH (natural pH of effluent) using 80 mg/L chitosan and 89% in mutual pH (pH level of 7.5) using 20 mg/L chitosan, while the COD removal efficiency is observed to be 65 and 73%and coliform removal efficiency is 97 and 94% respectively. Based on the statistical analyses, it is suggested to use Quartic model to model chitosan performance in turbidity removal and Quadratic model to model it in COD removal. The optimization results indicate that using 20 mg/L chitosan in pH range of 6.6 to 7, turbidity removal could be achieved near 100% and COD removal about 77%. Poly aluminum chloride functions well just in acidic pH making light flocs. The highest turbidity removal was observed about 88% in pH 5 using poly aluminum chloride doses of 100 and 150 mg/L. Statistical analyses suggest Quadratic model for turbidity removal predicting the highest efficiency about 90% in pH 5 using 140 to 150 mg/L poly aluminum chloride. Ferric chloride has the best function in mutual pH, achieving 88% turbidity removal efficiency using 200 mg/L coagulant. However the folcs are light and unsettlable, changing the effluent color in high doses. Based on the optimization results, 94% turbidity removal efficiency is predicted using 200 mg/L ferric chloride in pH range of 8.2 to 8.4. Comparing the results, less coagulant consumption, lack of necessary changes in the pH of effluent, producing denser flocs and not changing the effluent color could be pointed out as the advantages of chitosan over poly aluminum chloride and ferric chloride. Based on this study, chitosan has an adequate performance qualifying the waste stabilization ponds effluent for reuse or discharge receiving waters. Key words : algae removal, waste stabilization ponds, coagulation and flocculation, chitosan