Nonlinear Programming Model of Wastewater Treatment Plant

The optimal design of a wastewater treatment plant involves two complementary aspects—the mathematical model and the optimization technique—both of which have to be equally developed. This was seldom the case in previous literature. A complete mathematical model is described reflecting the operation of a treatment plant including six units (primary settler, aerator, final settler, thickener, anaerobic digester, and vacuum filter). Although many of the basic relationships come from the literature, some new equations and concepts are proposed. Basically, these are based on the disaggregation of the waste load into four components (biodegradable and nonbiodegradable suspended solids, biodegradable dissolved solids, and biomass). The model equations described the evolution of each of these components during biological and physicochemical phenomena occuring in the treatment plant. The development of an efficient optimization method and the results from various runs are reported in a companion paper.