Optimal Operation of Water Distribution Pumps Considering Water Quality

Abstract

A new methodology has been developed for determining the optimal operation of water distribution system pumps with water quality considerations. The methodology is based upon describing the operation as a discrete time optimal scheduling problem that can be used to determine the optimal operation schedules of the pumps in distribution systems. The solution methodology is based upon a mathematical programming approach resulting in a large-scale nonlinear programming problem that cannot be solved using existing nonlinear codes. The solution of the optimization problem is obtained by interfacing a hydraulic and water quality simulation code, EPANET, with a nonlinear optimization code, GRG2. Bound constraints on the state variables are incorporated into the objective function using the augmented Lagrangian penalty method. Three objective functions were used in the model to minimize (1) the deviations of actual substance concentrations from desired concentration values; (2) the total pump duration times; or (3) the total energy cost. The effectiveness of the methodology was tested using a hypothetical water distribution system. All three objective functions were capable of finding an optimal pumping schedule with water quality considerations.