Tracer Dispersion Studies for Hydraulic Characterization of Pipes

A series of experiments were conducted at the U.S. Environmental Protection Agency (EPA) Test & Evaluation (T&E) Facility in Cincinnati, Ohio, to quantify longitudinal dispersion of a sodium fluoride tracer in polyvinyl chloride (PVC) pipe and ductile iron pipe under laminar, transitional, and turbulent flow conditions. The tracer injection durations were varied at different flow conditions to study their impacts on the tracer transport characteristics. Pitot-tube type sampling ports were built into the pipe systems to study the in-pipe behavior of the tracer and identify the optimal sampling position. Preliminary tests confirmed the linear relationship between conductivity and fluoride, as published in previous EPA studies. Thereafter, conductivity (measured using online sensors) was used to characterize the dispersion and diffusion of the tracer material. The experiments indicate that the amount of tracer measured decreased with increase in flow rate regardless of pipe material. This observation supports the theory that there may be an increase in adsorption/reaction phenomena observed with increases in velocity. This result, if confirmed with the upcoming chlorine/chloramine disinfectant kinetic studies, may have an impact on how distribution systems are operated and modeled.