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Numerical Modeling of Premise Plumbing Systems Considering Dispersion Effect
Citation:
Woo, H., J. Burkhardt, L. Rossman, J. Mason, AND R. Murray. Numerical Modeling of Premise Plumbing Systems Considering Dispersion Effect. ASCE EWRI 2019, Pittsburgh,PA, May 19 - 23, 2019.
Impact/Purpose:
The purpose of this effort is to improve the modeling of water quality in premise plumbing system by considering dispersion effects. This work supports NRMRL, NERL and Office Water by improving the capabilities associated with modeling water quality in premise plumbing systems. No results are presented in this abstract.
Description:
The presence of contaminants in drinking water premise plumbing systems (PPS) remains a significant public health issue. Water quality in plumbing can be affected by various factors such as pipe materials, pipe scales, water chemistry, and water usage patterns. Intermittent water usage, that is common in buildings, translates to prolonged stagnation periods which complicates the assessment of contaminant movement and occurrences within PPS (Burkhardt et al., 2018). Modeling water quality in PPS must incorporate the transition from stagnant to flowing conditions and the impact of different flow regimes. Many uses in a building occur at low flow rates (such as from a refrigerator, ice machine, and a cup of water) which result in changes in water quality concentrations that are impacted by axial dispersion under laminar flow regime. Limited research has been conducted for modeling the fate and transport of contaminants in a PPS using EPANET (Grayman et al., 2006, 2008, Samuels et al., 2010). However, EPANET only includes advectional transport, which fails to consider the impact of dispersive effects on chemical species. In this study, the solute transport mechanism in PPS was investigated by solving the one-dimensional advection-dispersion-reaction equation using the adaptive operator-splitting technique or the Eulerian-Lagrangian method. The advection-reaction equation was calculated by using the method of characteristics in the Lagrangian method, and then the dispersion equation was calculated using the Eulerian method. Both explicit, forward-time-central-space (FTCS), and implicit, backward-time-central-space (BTCS), finite difference methods were implemented for calculating dispersion effects. Dispersion coefficients for laminar, transitional and turbulent flow regimes were previously calculated based on tracer test results (Woo et al., 2018). Water quality samples collected from a home plumbing system simulator (HPSS)—operated to simulate a realistic usage pattern within a four-person residence—were compared to model results that were generated using either FTCS and BTCS dispersion implementations. Samples collected from the HPSS include sequential samples from all faucets and samples collected during normal operations throughout the period of operation. The results of this study will be used to improve future assessments of the risk of exposure to contaminants within premise plumbing systems.