The present study focuses on understanding the internal hydraulic efficiency of baffled disinfection contact tanks using Computational Fluid Dynamics (CFD). In particular, we seek to address the key question: for a given footprint of a contact tank, how does the hydraulic efficiency of the tank depend on the number and geometry of internal baffles? In an effort to address this question, we perform high resolution two-dimensional (planar) simulations to quantify the efficiency of a laboratory scale tank as a function of the number of baffles. Simulation results of the velocity field highlight dead (stagnant) zones in the tank that occur due to flow separation around the baffles. Simulated longitudinal velocity profiles show good agreement with previous experimental results. Our analysis of Residence Time Distribution (RTD) curves obtained for different number of baffles for a given footprint of a tank indicate that there may be an optimum number of baffles for which near plug flow conditions is maximized. This study highlights the increasing role and value of CFD in improving hydraulic design characteristics of water engineering structures.