Synthesis and Design of Combined Biological Nitrogen and Phosphorus Removal WWT Plants

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

San Salvador de Bahia, Brasil

Congreso; PSE2009, 10th International Symposium on Process Systems Engineering -; 2009

Elsevier

optimization of the process configuration and equipment dimensions- i.e., process synthesis and design- and the operation conditions of activated sludge wastewater treatment plants (Alasino et al., 2007) will be extended to account for phosphorus as well as nitrogen removal. Continuous operation is supposed, and the influent wastewater flowrate and composition are assumed known. The performance criterion selected is to minimize the net present value including investment and operating costs while verifying compliance with the effluent permitted limits. The Activated Sludge Model No. 3 extended with the Bio-P module for computing biological phosphorus removal is used to model the reaction compartments, and the Takàcs model for representing the secondary settler. In the present work, new variables and equations for components accounting for phosphorus removal processes are incorporated and the superstructure is also enlarged to embed the most widely used combined N and P removal process configurations. Therefore, the complexity of the problem has been increased. The problem is posed as a NLP problem, specifically a nonlinear programming problem with discontinuous derivatives -DNLP-, as it results in a highly nonlinear system with non-smooth functions. The model is implemented and solved using General Algebraic Modelling System (GAMS), and proved to be robust and flexible. Results for case studies are presented and discussed. The Activated Sludge Model No. 3 extended with the Bio-P module for computing biological phosphorus removal is used to model the reaction compartments, and the Takàcs model for representing the secondary settler. In the present work, new variables and equations for components accounting for phosphorus removal processes are incorporated and the superstructure is also enlarged to embed the most widely used combined N and P removal process configurations. Therefore, the complexity of the problem has been increased. The problem is posed as a NLP problem, specifically a nonlinear programming problem with discontinuous derivatives -DNLP-, as it results in a highly nonlinear system with non-smooth functions. The model is implemented and solved using General Algebraic Modelling System (GAMS), and proved to be robust and flexible. Results for case studies are presented and discussed. Keywords: activated sludge process, combined N and P removal : activated sludge process, combined N and P removal