Combined nitrogen and phosphorus removal. Model-based process optimization.

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

Lyon, France.

Congreso; ESCAPE18 - 18th European Symposium on Computer Aided Process Engineering.; 2008

IFP Institute Francais de Petrole

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 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. Cost improvements of more than 10% with respect to conventional operating conditions are achieved.