Tracer experiments with lithium chloride to evaluate the hydrodynamics of constructed wetlands. Comparison of alternative analytical methods

The characterization of water flow dynamics (hydrodynamics) through constructed wetlands is relevant for optimizing wastewater treatment. Although constructed wetlands consist of simple systems, the water flow is complex and irregular, therefore, the study of hydrodynamics requires the use of experimental technics such as tracer experiments. To evaluate the effects of the use of three different analytical methods to compute the concentration of lithium chloride on the main hydrodynamics parameters, tracer experiments were conducted in ten independent lab-scale constructed wetlands. The concentration of lithium chloride in the output flow of the wetlands was calculated by flame photometry, electrical conductivity using a calibration curve and electrical conductivity using the salt molar conductivity. The paired samples T-test or the non-parametric Wilcoxon’s Signed-Ranks test were used to demonstrate that the computed hydraulic retention time and the number of tanks accordingly with the tanks-in-series model were not significantly affected by the selected analytical method.