Combined Nitrogen and Phosphorus Removal Model-Based Process Optimization

NOELIA ALASINO; MIGUEL C. MUSSATI; NICOLÁS SCENNA; PÍO AGUIRRE

Lyon, Francia

Congreso; 18th European Symposium on Computer Aided Process Engineering – ESCAPE 18; 2008

An optimization model based on a superstructure embedding several activated sludge process configurations for nutrient removal is formulated and solved. Simultaneous optimization of the process configuration (process synthesis) and operation conditions for given wastewater specifications and influent flow rate in steady state operation are investigated. The performance criteria selected is the total annual operation cost minimization while predicting compliance with the effluent permitted limits. As the piece of equipment is supposed given, investment costs are not considered. The Activated Sludge Model No. 3 extended with the Bio-P module for computing biological phosphorus removal are used to model the reaction compartments, and the Tákacs model for representing the secondary settler. The resulting mathematical model is a highly non-linear system, formulated as a Non-Linear-Programming Problem, specifically as a DNLP. The model is implemented and solved using GAMS and CONOPT, respectively. The optimal solution computed from the superstructure model provides cost improvements of around 10% with respect to conventional processes.