The paper presents a methodology which will arrive at an optimal capital investment schedule while considering the various parameters relevant to wastewater treatment. The primary emphasis is on the development of a methodology which is flexible enough to accomodate any factor which one might reasonably wish to include. The program has been designed to optimize a combination of processes or to optimize the individual processes separately. The model generates the optimal capacity schedule within its limited discrete universe. These solutions agree with the analytical expectations for simple demand curves of linear or geometric shape. In addition, the model provides a cheap and convenient means of exploring alternate futures in actual decision making situations. At the least it provides some method of calculating the cost of forecasting errors.