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  • 1
    Publication Date: 2017-04-04
    Description: Typical unsteady unsaturated conditions can profoundly affect the hydrodynamics of vertical subsurface flow constructed wetlands. In this study we analyzed the hydrodynamics of a 33 m2 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 20 cm 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 by means of both a classical residence time distribution analysis and an originally developed numerical plug-flow 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 14 cm 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.
    Description: Published
    Description: 265-273
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: Constructed wetlands ; Vertical flow ; Hydrodynamics ; Tracer tests ; Rhodamine WT ; Modelling ; Unsaturated flow ; Dispersivity ; 03. Hydrosphere::03.02. Hydrology::03.02.06. Water resources ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.01. Environmental risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
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  • 2
    Publication Date: 2017-04-03
    Description: This paper introduces a mathematical model (FITOVERT) specifically developed to simulate the behaviour of vertical subsurface flow constructed wetlands (VSSF-CWs). One of the main goals of the development of FITOVERT was to keep the complexity of the model to an acceptable level, so as to provide a practical tool for design and operation optimization. The dynamic formulation of the model allows to simulate the typical non stationary feeding-emptying operation of VSSF-CWs. FITOVERT is able to describe the water flow through porous media in unsaturated conditions, combined with evapotranspiration; its biochemical module describes the degradation of both organic matter and nitrogen; the transport in the liquid phase is implemented for both dissolved and particulate components; the oxygen transport in the gaseous phase of the soil and its exchange with the liquid phase are also considered. As a main advantage, compared to the few currently available dedicated numerical models, FITOVERT is able to handle the porosity reduction due to bacteria growth and accumulation of particulate components, so that the clogging process is also simulated as an effect of the pore size reduction on the hydraulic conductivity of the simulated system. The performance of the model was firstly analyzed by comparison with hydrodynamic tests recorded in an experimental VSSF-CW pilot plant: tracer test were carried out in three different saturation conditions (fully saturated, partially saturated, and completely drained). FITOVERT proved to accurately simulate the hydraulic behaviour of VSSF-CWs in both saturated and unsaturated conditions. The needs for model improvements and further calibration are finally discussed.
    Description: In press
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: Constructed wetlands ; Hydrodynamics ; Modelling ; Reactive transport ; Vertical subsurface flow ; Unsaturated flow ; 03. Hydrosphere::03.02. Hydrology::03.02.06. Water resources ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.01. Environmental risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
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  • 3
    Publication Date: 2017-04-04
    Description: This paper introduces a mathematical model (FITOVERT) specifically developed to simulate the behaviour of vertical subsurface flow constructed wetlands (VSSF-CWs). One of the main goals of the development of FITOVERT was to keep the complexity of the model to an acceptable level, so as to provide a practical tool for design and operation optimization. The dynamic formulation of the model allows to simulate the typical non stationary feeding-emptying operation of VSSF-CWs. FITOVERT is able to describe the water flow through porous media in unsaturated conditions, combined with evapotranspiration; its biochemical module describes the degradation of both organic matter and nitrogen; the transport in the liquid phase is implemented for both dissolved and particulate components; the oxygen transport in the gaseous phase of the soil and its exchange with the liquid phase are also considered. As a main advantage, compared to the few currently available dedicated numerical models, FITOVERT is able to handle the porosity reduction due to bacteria growth and accumulation of particulate components, so that the clogging process is also simulated as an effect of the pore size reduction on the hydraulic conductivity of the simulated system. The performance of the model was firstly analyzed by comparison with hydrodynamic tests recorded in an experimental VSSF-CW pilot plant: tracer test were carried out in three different saturation conditions (fully saturated, partially saturated, and completely drained). FITOVERT proved to accurately simulate the hydraulic behaviour of VSSF-CWs in both saturated and unsaturated conditions. The needs for model improvements and further calibration are finally discussed.
    Description: Published
    Description: 633-640
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: Constructed wetlands ; Hydrodynamics ; Modelling ; Reactive transport ; Vertical subsurface flow ; Unsaturated flow ; 03. Hydrosphere::03.02. Hydrology::03.02.06. Water resources ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.01. Environmental risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
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