AWWA CSC95037

The water utility industry is striving to produce higher quality water at reduced costs. Improved process control through the introduction of new technologies has increased operational efficiency, however, there are still substantial benefits to be made by the proper choice of proportional gain and reset time constant of the ubiquitous PI controller. Unfortunately, even after careful instruction plant operators still have difficulty in installing and operating PI(D) systems. A feedback control system is of little value if it is improperly tuned. This paper describes the theory behind and the operation of some CAD software routines which help the process operator to: decide if PI(D) control is appropriate and if it is to select automatically values for the controller parameters, or; if PI(D) is not appropriate (for example, if the process is heavily dead-time dominant) it guides the user through the steps required to design and implement a simple predictive PI solution. The software has the potential to noticeably increase the efficient operation of water treatment plants.