Biological Process Optimal Design in a Wastewater Treatment Plant

1. Abstract The aim of this paper is to determine the optimal design and operation of an activated sludge system that is being installed in a small town in the north of Portugal. This process design takes into consideration real data in order to define the objective cost function which includes both investment and operation costs. The collected data were also used to characterize the wastewater in that region. To define the constraints of the optimization problem, we consider very well established models for the aeration tank and the secondary settler, together with the system balances and some system definitions. The highly nonlinear optimization problem was solved through the internet by the SNOPT solver provided by the NEOS Server. We found, for the minimum cost, the optimal design/operation for the above mentioned system in terms of the volume of the aeration tank, air flow needed for the biological sludge, the sedimentation area and the secondary settler depth, to name a few of the involved variables. 2.