Fundamental understanding of the complex behavior of small droplets or particles in wall bounded turbulence and their interaction with the surrounding fluid is critical in a number of industrial processes. One approach for gaining valuable insight is the direct numerical simulation (DNS) of turbulence in conjunction with numerical computation of particle trajectories. Most previous work was limited to dilute suspensions of non-colliding particles. Part I of this paper extends previous methods by allowing for interparticle collisions. Part II presents results for the rate of collision between aerosol droplets.