Today’s large wastewater treatment plants are becoming difficult to control. The sheer size and the complexity of the process has increased the amount of information necessary for the operator to make decisions. Computers are information processors and, as such, they can greatly enhance the operator’s ability to access information and execute control commands. Computer system design and implementation is a complex kind of work requiring careful planning. The role of the Consultant, Contractor, and Owner must be clearly defined to allow an orderly procession of the work. Careful planning and coordination throughout the design and construction can ensure that the system fulfills its purpose, thereby enhancing the operator’s ability to control the plant.