Planning Time-Phased Regional Treatment Systems

An economic optimization model for selecting least-cost regional wastewater treatment facility locations, interceptor routes, and capacity expansion schedules is developed. The model explicitly considers the interaction between facility location and capacity expansion decisions on total system cost. Cost functions for treatment facilities and interceptors and growth patterns for future wastewater flows may be of any form. The model is solved with a three-phase heuristic procedure that makes strong use of dynamic programming. In comparison with a mixed integer programming model on a large-scale problem the procedure demonstrates significant advantages in computational time, accuracy, and user requirements. The model is applied to facilities planning in a 208 study area of Massachusetts to demonstrate how the economic impacts of alternative management objectives and demographic projections can be assessed.