Diurnal variations of flow rate and organic load cause difficulties in the operation of wastewater treatment plants. The man-made hydraulic shocks produced by the installation of fixed speed pumps upstream of the treatment processes further amplify the frequency and magnitude of these variations. The major objective of this study is to develop control strategies to minimize these variations. A dynamic model has been developed for the operation of fixed speed pumping stations. The optimum control strategy based on this model can reduce the on-off pump cycles up to 86% for a typical day as compared with ordinary two point control. Optimum models and corresponding control algorithms have also been developed for the operation of in-line equalization basins. These models have shown potential for the reduction of the required equalization volume and can provide smoother outflow to the downstream processes. A reduction of tank volume by 63.5% has been obtained in the simulation using the optimum control strategy.