EPANET-BAM: Water Quality Modeling with Incomplete Mixing in Pipe Junctions

This paper describes a new water-quality model that allows incomplete mixing at pipe junctions in water distribution networks. The bulk advective mixing (BAM) model honors momentum transfer and separation of impinging fluid streams within a cross junction. The solution is predicated on observed flow patterns in computational fluid dynamics simulations, which were confirmed by experiments, and a mass balance that ensures solute mass is conserved. This paper focuses on the implementation of this new model in EPANET, software that models hydraulics and water quality in water distribution networks. In the new version, EPANET-BAM, a mixing parameter, s, is implemented that allows the user to select the bulk advective mixing model (s = 0), the existing complete mixing model (s = 1), or a result that is linearly scaled between the results of the two models. Aside from the mixing parameter, which has been added to the junction property field within EPANET, all other functions of the BAM model are transparent to users of EPANET-BAM. This paper presents an example of the use of EPANET-BAM and the potential impact of the new model on water quality predictions and risk assessments.