Optimum Design Of Activated Sludge PlantsUsing The Simulator Daisy 2.0

This paper presents the theoretical basis and some practical applications of the simulation program DAISY (Activated Sludge DYnamic simulator) version 2.0 with the aim of optimizing the design of complex activated sludge plants for wastewater treatment. The software, developed by CEIT, was designed for the Spanish firm CADAGUA S.A. and is currently used as design tool by the engineering department of the company. The new version of the simulator introduces an optimization module that estimates automatically the optimum dimensions and of an activated sludge plant to reduce the global cost function that could include effluent quality, construction cost and plant restrictions. This global cost function can combine continuous cost and penalty functions. The automatic optimization is based on a direct search algorithm introduced in the simulation software previously developed. This algorithm determines the path towards an optimum by evaluating the objective function at several points without calculating derivatives. The paper includes some examples to illustrate the vast possibilities of these kind of optimization procedures in the design of complex wastewater treatment plants including organic matter and nutrient removal.