The objective of this research was to apply a mathematical model to predict the performance of carbon beds in removing humic substances. Data obtained from the model predictions can be useful in designing a pilot-scale carbon bed for each different water treatment plant location. The model used in this study was originally developed and verified by Crittenden and Weber (1) for four organic compounds. The mathematical model considered film transfer and pore surface diffusion to limit the rate of adsorption. Lee (2) has found that orthogonal collocation is a more efficient and accurate solution technique than the finite difference method. Therefore, orthogonal collocation was used to solve the model’s differential equations for the work presented here instead of finite difference method used by Crittenden and Weber.