The coagulation, flocculation and sedimentation processes involve many complex physical and chemical phenomena and thus are difficult to model using traditional methods. This paper proposes the use of a neural network model for these treatment processes. A brief review of artificial neural network (ANN) models is presented, followed by a description of the development of an ANN model for a large water treatment plant. To show the capacity of the ANN model, a scenario analysis was performed to highlight important operational parameters. A neural network process model was built based on nearly 2,000 sets of process data. The model was shown to be capable of adequately predicting system performance.