Predictive On-off Cost Minimizing Control of a Municipal Waste Water Treatment Plant

With intermittently operated municipal waste water plants the aeration switching sequence should be optimized under the constraints that the solved nitrogen concentration in effluent has to be kept within its environmental limits. This is a highly nonlinear control problem because of the nonlinear biological process model ASM1 (Activated Sludge Model 1), the on-off state of the manipulated sequence and the concentration constraints. The constrained optimization was transformed to the unconstrained optimization of the predictive on-off control, as the violations of the constraints were converted to their economical costs. Furthermore, the cost of the aeration was considered in the cost function. Copyright © 2005 IFAC