The study of flocculation in Couette flocculators showing Taylor vortices and subsequent solid-liquid separation characteristics were conducted experimentally. In continuous experiments two flocculators were used to ex-tract the hydrodynamic similarity and proper parameters for the flocculator scale-up. The optimum retention time was found about 150-180 seconds in the present experiments. Also, optimum flocculation conditions in two flocculators were reached at the same rotational speed of the inner cylinder. With these results a correlation of the optimum Taylor number was obtained as a function of the scale-up factor, the suspension concentration and the flocculant concentra-tion. To facilitate the solid-liquid separation an inclined plate settler was attached to the Couette flocculator. Through continuous experiments in this combined apparatus it was found that the separation performance was excellent. All these results show that the Couette flocculator with the mclmed plate settler may be used efficiently in solid-liquid separation.