Please use this identifier to cite or link to this item:
AuthorsGiraldi, D.* 
De' Michieli Vitturi, M.* 
Zaramella, M.* 
Marion, A.* 
Iannelli, R.* 
TitleHydrodynamics of vertical subsurface flow constructed wetlands: Tracer tests with rhodamine WT and numerical modelling
Issue Date2008
KeywordsConstructed wetlands
Vertical flow
Tracer tests
Rhodamine WT
Unsaturated flow
Subject Classification05. General::05.08. Risk::05.08.01. Environmental risk 
AbstractTypical unsteady unsaturated conditions can profoundly affect the hydrodynamics of vertical subsurface flow constructed wetlands. In this study we analyzed the hydrodynamics of a 33m2 vertical flow pilot plant, treating municipal secondary effluents. Three different saturation conditions were analyzed under several constant flux regimes: complete saturation, partial saturation with the free water table 20cm over the bottom of the bed, and complete drainage. Tracer tests were performed in steady state conditions by dosing rhodamine WT as square input signals. Breakthrough curves were analyzed both by means of a classical residence time distribution analysis and an originally developed numerical plugflow model with longitudinal dispersion adapted to the unsaturated conditions. We found that the degree of global mixing in the vertical flow constructed wetland increased as the water content increased; this effect was controlled by the hydraulic residence time of the system. Conversely, the degree of local mixing was inversely affected by water content; the dispersivity was 4.5, 10, and 14cm for fully saturated, partially saturated and draining conditions, respectively. We explain the dependency of dispersivity on water content in physical terms, however, further studies are needed to mathematically include this relationship in numerical models that describe the behaviour of vertical flow constructed wetlands.
Appears in Collections:Papers Published / Papers in press

Files in This Item:
File Description SizeFormat 
EE_PP_Giraldi et al_2008.pdf611.51 kBAdobe PDFView/Open    Request a copy
Show full item record

Page view(s)

checked on Apr 29, 2017


checked on Apr 29, 2017

Google ScholarTM