Capacity Expansion for Regional Wastewater Systems

Abstract

A simple yet effective approach is presented for solving regional wastewater treatment system capacity expansion problems. The approach decomposes a model into two levels, upper and lower. The lower level treats the subproblems related to separate facilities of a regional treatment system. These subproblems are solved independently by dynamic programming. The upper level is used to coordinate the subproblems in the lower level and is updated using a random polyhedron search algorithm that identifies progressively superior solutions. Constraints imposed on treatment plant or transfer capacities are considered first, and then constraints relating to the in‐stream quality of the receiving water are incorporated. The procedures developed are tested in a hypothetical problem with seven communities along a river and its tributary. The results obtained indicate that it is economically attractive to consider time‐staging of capacity whenever possible. It is also observed that the model with in‐stream quality constraints required more computational resources, the amount of which is somewhat dependent on the level of in‐stream quality requirement imposed. However, the incremental computational efforts required might not be excessive.