Abstarct: Heavy mextals are one of the sources of contaminants in water. Hexavalent chromium is one of the very toxic and hazardous heavy mextal that exceeding its concentration in drinking water from 50 ppb causes water pollution and carcinogenicity. Naturally dissolution of chromium minerals in water is the common sources of chromium in groundwater and surface water. In this study, the removal of chromium from drinking water by precipitation using reducing and coagulant agents such as ferrous iron and lime have been investigated. In this research, the effect of different parameters such as optimum ferrous iron concentration, effective alkalinity, velocity gradient and retention time for chromium removal from aqueous solution were investigated by tow optimization methods such as step by step and Taguchi approaches. All experiments were performed at laboratory temperature in the range of 20 to 25 ° C. The results of pilot study showed that the most critical factor in the chromium precipitation process is the concentration of the reducing agent but this factor alone is not sufficient and due to the consumption of alkalinity, sufficient alkalinity is the second important factor for better and more economical removal of chromium. To optimize ferrous iron concentration, four different stoichiometric ratios were investigated. The results showed that from 0.5, 1, 1.5 and 2 stoichiometric ratios, the ratio of 1 is the most economical ferrous reducing agent concentration. Also, to evaluate the mixing intensity, the velocity gradient parameter (G) with 5 different values was evaluated. The results showed that the optimum gradient was 22.65 s-1 for both economically and chromium removal efficiency aspects. In addition, the optimum amount of alkalinity addition to water to remove chromium is 98-170 mg / L as CaCO3. The optimum sedimentation time was also determined from one to three hours.