AWWA WQTC52862

Residence time (RT) is the time it takes water parcels in a distributionsystem (DS) to reach a specific location. The velocity of water in the pipes affects the RT, which may change both spatially and temporally because of daily demand variations, pipe diameter, and storage capacity. Hydraulic and water quality models, such as EPANET, are capable of predicting temporal variations of RT, referred to as water age (WA), at any location of the DS. Practical and reliable applications, however, require a significant investment in time and money for calibration and verification of such models, especially in large and complex distribution systems. The method proposed in this paper to estimate the mean constituent residence time (MCRT) is based on the analysis of the fate of fluoride, a conservative tracer introduced to the water treatment plant and followed throughout the DS. This research examines the calculation of MCRT independent of network modeling. The DS of Raleigh, North Carolina was selected as a case study because both a network model and extensive fluoride tracer studies were available. Includes 5 references, tables, figures.



Keywords: Modeling;Fluoride;Distribution Systems;Tracers;Pipes;Water Quality;North Carolina;Velocity;Sampling