This paper aims to investigate the performance of the rice starch in potable water treatment and optimize the operating conditions to evaluate the feasibility of rice starch to be applied in the potable water treatment industry. Rice starch was found to be an anionic polymer and gelatinized at 83 °C in this study. Response Surface Methodology (RSM), a statistical experimental design was adopted to optimize the turbidity reduction with the dosage of rice starch, pH and settling time as control factors. The interaction between the factors was discussed. Maximum turbidity reduction (>89) can be achieved through optimum conditions of 9.64 mg/L dosage of conventional rice starch and 20 min of settling time at pH 3. Bridging and absorption was proposed as the flocculation mechanism of rice starch in drinking water treatment and have been preliminarily proven through the observation of floc under the microscope. Based on the results obtained, rice starch can be considered as a potential natural coagulant for potable water treatment. © 2019 Taylor & Francis Group, LLC.