Bounded Implicit Enumeration for Wastewater‐Treatment Systems

Abstract

A wastewater‐treatment system can be represented by a multistage configuration consisting of a variety of unit processes from various stages. The number of treatment combinations may be very large when the number of unit processes in a stage and the number of stages in a system increase. Enumeration techniques, e.g., total enumeration and implicit enumeration, have been used to eliminate infeasible treatment combinations and to identify the least‐cost treatment system. A bounded implicit enumeration approach is proposed to make the implicit enumeration more efficient. A lower bound is calculated at each stage and added to the up‐to‐date objective function value to eliminate more combinations before reaching the final stage. The results for two wastewater‐treatment‐system‐synthesis models indicate that the bounded implicit enumeration is consistently more efficient than the total and implicit enumeration approaches in identifying least‐cost and feasible treatment alternatives.