Knowledge-based supervision and control of wastewater treatment plant: a real-time implementation

The hardware architecture and the software development of a real-time knowl edge-based distributed control system for the supervision of a wastewater t reatment pilot plant are presented. The operation scheme is based on an A(2 )/O system (anaerobic, anoxic, oxic) and includes organic matter removal, n itrification/denitrification, and Enhanced Biological Phosphorous Removal ( EBPR). The hardware architecture involves different supervision levels, inc luding two autonomous process computers (plant control and analysers contro l) and a PLC. The software architecture includes a Knowledge-Based Expert S ystem (KBES) as the top control system. The KBES has been developed in G2, an expert system development environment based on object-oriented structura l design. This system is fed with data obtained from the plant monitoring ( in-line, on-line and off-line data) and with actuation data of the lower co ntrol levels. Using this information, the KBES supervises the pilot plant i n order to help with fault detection and plant maintenance, but also modifi es setpoints and other variables of the local control level to adapt the sy stem to the different influent conditions. The overall system has been impl emented and validated at pilot scale.