This paper discusses the development of a three-dimensional Euler-Lagrange CFD model for a gas-liquid bubble column. The model resolves the time-dependent, three-dimensional motion of small, spherical gas bubbles in a liquid. Our model incorporates all relevant forces acting on a bubble rising in a liquid, and accounts for two-way momentum coupling between the phases. The liquid-phase hydrodynamics are described using the volume-averaged Navier-Stokes equations for laminar flow. This three-dimensional CFD model is used to study the effect of the aspect ratio of the bubble column on the flow pattern.