FUZZY-LOGIC PROCESS-CONTROL OF HPO-AS PROCESS

The high purity oxygen activated sludge process requires more advanced controls as compared to the conventional activated sludge process. Fe edback controllers have difficulty controlling process disturbances du e to process delays and noisy signals, and cannot adjust to extreme up sets, such as stormwater hows. Four fuzzy logic control systems were d eveloped for average conditions, and are superior to conventional feed back control systems in conserving energy, reducing dissolved oxygen ( DO) variations, and stabilizing feed and exit gas how rates. A direct control strategy, using feedforward aerator speed control and feedback stage 4 DO control, is the best among the four systems. For plants wi thout variable speed aerators, feedforward control based on influent f low rate to adjust the stage 1 pressure setpoint, with feedback stage 4 DO control, is best. To address stormwater flows an adaptive fuzzy l ogic central system was developed. The control system can immediately shift to a new state to adapt to large changes in influent flow rate. The system prevents DO depletion under wet weather conditions, and con serves oxygen and energy during dry weather conditions.