We have carried out Brownian dynamics simulations of sedimentation phenomena of a dispersion composed of two-kinds of spherical particles under the gravity field. This study may be the first step to develop a new technology which enables us to improve the visibility of rivers and lakes. In the present study, we have modeled sub-micrometer-dimension particles, or dirty particles, as small spherical particles, and capturing particles as large spherical particles; these two-kinds of particles conduct Brownian motion in water, and large particles adsorb small particles to sediment gradually toward the bottom in the gravity field. From the results of simulations, the influences of Brownian motion, the size of each particle, and the gravity force on the performance of the adsorption of large particles have been discussed. In addition, we have discussed what the most appropriate situation of large particles is to accomplish the most effective adsorption rate or improve the visibility of water most effectively in terms of capturing particles. The most important conclusion derived from the present results is that, in order to improve the capturing performance, the Brownian motion of large particles has to be activated in an appropriate number density without losing the influence of the gravity. (C) 2009 Elsevier Inc. All rights reserved.