Multicriteria control strategy for cost/quality compromise in Wastewater Treatment Plants

Because of their complex behavior, activated sludge processes are very difficult to control. A comparative study of control performances, based on modifications of the Benchmark reference control scheme, shows that these have limited effect on the treatment efficiency. For this reason, a new strategy has been studied: the choice of the manipulated and measured variables is based on a sensitivity analysis on an accurately reduced model. The effluent quality is strongly improved, though the global cost is increased. Finally, a multicriteria control strategy is proposed to decrease the global cost although keeping good performances with a Takagi-Sugeno fuzzy supervisor being developed in order to smooth the switching. As expected this strategy provides good performances, and in addition this control would be very simple to implement on a real process. (C) 2003 Elsevier Ltd. All rights reserved.