Mohammad Yousefi - ۱Department of Civil Engineering, Faculty of Engineering, University of Qom, Qom, Iran.
Ehsan Jabbari - ۱Department of Civil Engineering, Faculty of Engineering, University of Qom, Qom, Iran.
Mehdi Sedighi - Department of Chemical Engineering, Faculty of Engineering, University of Qom, Qom, Iran.

Water shortages and pollution are so severe that the last decade has been called the international decade for water. In water treatment plants, coagulation and flocculation are used to remove turbidity. This study examined the use of naturalcoagulants and its efficiency compared with existing coagulants. Response surface methodology was used to design the experiments. Type of coagulant and coagulant aid, as well as pH, were considered important factors during experiments. Results of the tests indicate that pH has a significant impact on turbidity removal. The combination of chitosan and polyaluminum chlirode reduces water turbidity effectively. A combination of polyaluminum chlirode (۷.۶ mg/L) and chitosan (۹.۲۸ mg/L) at pH= ۸.۵۲ removed ۹۹.۸۵ % of the turbidity. Accordingly, the combined use of polyaluminum chlirode and chitosan reduced the amount of material and enhanced turbidity removal.

Turbidity Removal, coagulation, Chitosan, Polyaluminum Chloride, Optimization