Nowadays, constructed wetlands (CW) systems are an important wastewater treatment option. Subsurface flow (SSF) constructed wetlands are one of the main types which are being used, and in researches, these systems dyes tracer experiments are an appropriate tool to determine residence time distribution (RDT) curves and parameters of hydrodynamic models, as a wetland dispersion numbers and hydraulic efficiency. The objectives of this paper are to evaluate and compare the performance of two fluorescent tracers (rhodamine WT and sodium fluorescein) on subsurface-flow CWs hydrodynamic characteristics determination. The cells were operated at actual hydraulic residence time (τR) of a 4.5 d ~ 5.0 d range and the parameters of theoretical models were obtained for each system, indicating very low dispersion. The CWs with length/widths ratio equals to 24 presented as plug flow near systems. Although the recovery of total amount was small (high absorption is one of the loss mechanisms during these types of studies), rhodamine WT is a suitable tracer in mesocosms SSF constructed wetland systems of study.
hydrodynamic behavior; residence time distribution; sodium fluorescein; wetland dispersion number; rhodamine WT; constructed wetlands
