JOURNAL OF THE ENVIRONMENTAL ENGINEERING DIVISION COST INTERACTIONS IN ACTIVATED SLUDGE SYSTEMS

Wastewater treatment plants are complicated systems consisting of several interacting processes. The design, operation, and control of these plants is not a simple task, since most of the processes that make up the plant, and the interactions among these processes, are not precisely understood. Moreover, the environment in which the plant functions is continually changing, and is often uncertain. However, the analysis of complex systems, such as a wastewater treatment plant, has been facilitated by new analytical techniques, and computers. Several investigators have focused their attention on the problems of optimal plant design and operation. Smith (16) was one of the earliest to study the effects of interactions in processes. He developed a steady-state design program that was capable of sizing the unit processes normally found in wastewater treatment plants. His program also estimated the cost of the facilities, given baseline cost parameters. Parker and Dague (12) developed an optimal, steady-state design procedure for wastewater treatment plants composed of a primary clarifier, an activated sludge process, and an aerobic digester. These author