Observer-based time-optimal control of an aerobic SBR for chemical and petrochemical wastewater treatment

The present study implements a time-optimal control strategy for a disconti nuous aerobic bioreactor, used to treat highly concentrated toxic wastewate r present in some effluents of the chemical and petrochemical industries, u sing respirometric techniques. The control strategy regulates the feed rate to maintain a constant optimal substrate concentration in the reactor, whi ch in turn minimizes the reaction time. Since this control requires on-line knowledge of unmeasurable variables, an Extended Kalman Filter is used as a nonlinear observer. The experimental setup was a 7 litre laboratory biore actor used to treat synthetic wastewater with high concentrations of 4-chlo rophenol. The controller consisted of a personal computer with data acquisi tion hardware and real-time software tools, peristaltic pumps and an electr onic oxygen meter. Three experiments were performed: one to obtain paramete rs and calibrate the observer, another one to validate the time-optimal str ategy and a final one to evaluate the performance of a fully automated time -optimal operation. When well calibrated, the observer provided good enough estimates and the controller worked as expected, reducing reaction time an d increasing the overall efficiency of the bioreactor, when compared with t he usual SBR-type operation.