Modeling reaction and transport of multiple species in water distribution systems.

A general framework for modeling the reaction and transport of multiple, interacting chemical species in drinking water distribution systems is developed. It accommodates reactions between constituents in both the bulk flow (through pipes and storage tanks) and those attached to pipe walls. The framework has been implemented as an extension to the well-known EPANET programmer's toolkit (a library of functions that simulates hydraulic behavior and water quality transport in pipe networks). The implementation allows modelers to define the particular species of interest and their chemical equilibrium and reaction rate equations in a natural fashion using standard functional notation. It also employs several different numerical methods, including a stiff differential equation solver, to solve the reaction/equilibrium system throughout the pipe network using the standard EPANET transport algorithm. The flexibility and power of the framework is demonstrated with two examples that model water quality dynamics governed by different reaction/equilibrium systems.