Preliminary Optimal Design Model for Wastewater Treatment Plant

Abstract

A mathematical programming model for the least-cost design of a wastewater treatment plant is presented for the preliminary screening of projects. This model represents the treatment plant as a network of unit processes and uses a cost function that depends not only on waste removal efficiency, but also on influent flow rate and concentrations of various effluent quality criteria, such as biochemical oxygen demand, phosphorus, and nitrogen. The model also incorporates the concept of generalized bypass piping, allowing a bypass after each unit process, which makes it possible to enhance the flexibility and economy of designs. The proposed approach facilitates a number of important decisions for the optimal design of wastewater treatment plants, especially selection of the combination of unit treatment processes, their sizes and removal efficiency levels, and the flow distribution. Since the cost functions are simplified in this model, more elaborate mathematical programming models should be used to reach a final decision.