Storage Tank Mixing Models: Comparison of Tracer Data with Model Simulation

Analyses of water distribution systems serving base housing have been conducted as part of an epidemiological study of exposure to contaminated drinking water at U.S. Marine Corps Base Camp Lejeune, North Carolina. These analyses have included conducting tracer studies and constructing water distribution system models. During the conduct of the tracer studies, it appeared that water in storage tanks was not mixing completely or uniformly. As a result, controlling storage tanks were equipped with continuous recording water-quality monitoring equipment to record fluoride concentrations during fill and drain cycles. Additionally, different storage tank mixing model concepts were tested during the water distribution system model simulation process. The storage tank mixing models tested included complete mixing, two-compartment mixing, first-in first-out plug-flow mixing, and last-in first-out plug-flow mixing. In this paper the authors present comparisons between the tracer study field data and the four simplified storage tank mixing models.