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Modeling of Dispersion Effect for Intermittent Flow in Premise Plumbing Systems
Citation:
Woo, H., J. Burkhardt, L. Rossman, J. Mason, AND R. Murray. Modeling of Dispersion Effect for Intermittent Flow in Premise Plumbing Systems. In Proceedings, 1st International WDSA/CCWI 2018 Joint Conference, Kingston, Ontario, CANADA, July 23 - 25, 2018. Queen's University, Kingston, Canada, 99-99, (2018).
Impact/Purpose:
The purpose of this work was to describe the importance of including dispersion in water quality modeling for premise plumbing systems. This work is associated with a larger effort to model exposure risks associated with premise plumbing systems. This paper provides an introduction to the subject, and is associated with an upcoming presentation that will be given to the WDSA/CCWI joint conference. Understanding the impact of dispersion will help to improve predictions of water quality within premise plumbing systems.
Description:
Modeling tools for water distribution systems have been developed and used for many years, however, only limited attention has been given to home or premise plumbing modeling. Recent issues in Flint, MI highlighted the need for understanding premise plumbing systems (PPSs) and their unique characteristics and contaminants (e.g., lead from lead service lines). As a result of their intermittent operation and wide range of flow rates, modeling PPSs requires the inclusion of axial dispersion to accurately predict water quality variations. Flow in PPSs is typically stagnant with intermittent uses ranging from laminar to turbulent flow rates depending on the water uses in the fixtures. Specifically, low-velocity flows happen sporadically at times in a PPS (e.g., the uses from the ice machine and water line in the refrigerator, brushing the teeth, a cup of water, and various low flow devices). Flow under laminar conditions with low velocity and high dispersion can move contaminants at twice the speed of the average velocity. EPANET which has been widely used for the analysis of water distribution systems with reasonable accuracy does not calculate axial dispersion of low-velocity flow for the analysis of PPSs. The impact of dispersion on contaminant transport in PPSs has not been thoroughly investigated. The objective of this study is to investigate how dispersion will impact the predicted water quality when modeling PPSs. This study tested various approaches of including dispersion for PPS modeling and were compared to data collected in a pilot scale home plumbing system along with analytical solutions. In this study, the solute transport mechanism in PPSs was investigated by solving the advection-dispersion-reaction equations numerically.
