Abstarct: Very high turbidity is one of the major problems in the treatment of wastewater from stone processing units. This research aimed at removing the turbidity from wastewater of travertine processing industries using aluminum sulfate (Alum) and poly aluminum chloride (PAC) coagulants. In addition, properties of the formed flocs, including mean diameter, fractal dimension and rate of change in floc dimension, were assessed in this research by means of image processing. A series of pictures from sedimentation process of flocs were captured in 30-minute periods with three-second time interval, and were processed by MATLAB software. Moreover, the coagulation process for various concentrations of the applied coagulants was optimized, and the kinetics of the sedimentation process was assessed. Furthermore, changes in pH, EC, and TDS during the coagulation process were evaluated. The maximum percentage of removal of turbidity (99%) occurred at concentration of 50 mg/L for Alum and PAC coagulant. According to the results, the coagulation process decreased pH in the wastewater while it increased the levels of EC and TDS. On the other hand, the kinetic of reaction demonstrated that the turbidity reduction process started at a high rate (90-93% removal turbidity) during the first five minutes of sedimentation. In addition, the kinetic of floc sedimentation in the coagulation process was of the second order for both coagulants. Evaluation of the properties of flocs using image processing demonstrated that mean size of PAC flocs, compared to Alum, was larger at the start of sedimentation and smaller at the end of the process. Also, the fractal dimension and sedimentation rate of PAC flocs were higher than of Alum, which indicates that the shape of flocs of PAC are closer to a circle than of Alum. Furthermore, if the flocs are broken, their size, rate of change in their dimension and the fractal dimension decreased for both coagulants in re-sedimentation. In summary, the PAC coagulant had a more efficient usage in the remove of turbidity from travertine wastewater, compared to Alum.