Design configurations affecting flow pattern and solids accumulation in horizontal free water and subsurface flow constructed wetlands

Pedescoll, Anna; Sidrach‐Cardona, Ricardo; Sánchez, Joaquín Fernández; Carretero, J. Hernández; Garfí, Marianna; Bécares, Eloy

doi:10.1016/j.watres.2012.12.010

Cited by 56 publications

(23 citation statements)

References 25 publications

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“…The increased λ values when compared with the tests in winter indicate the positive effect of growing roots and rhizomes on the hydraulic performances of the three CWs. This has also been observed in previous research, where only the presence of plants seemed to help water to flow at least partially within the porous media; otherwise, water was shown to preferentially flow above the porous media, thus losing half the effective volume of the system [3,7,21]. The tracer recoveries of CW1, CW3, and CW6 were 72%, 82%, and 81%, respectively.…”

Section: Hydraulic Performancesupporting

confidence: 85%

“…In recent years, CW design has evolved to mitigate the adverse effects of clogging [4,7]. Previous studies aimed at increasing hydraulic retention time and maximizing contact opportunity between the substrate and wastewater to improve treatment performance [8].…”

Section: Introductionmentioning

confidence: 99%

“…It would also make the water flow pattern more uniform. Here, we must note that previous studies have predominantly been based on random selection of parameters [7]. No studies have accurately quantified water flow distribution by integrating different design parameters in CWs to improve hydraulic and treatment performance.…”

Section: Introductionmentioning

confidence: 99%

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Multilayer Substrate Configuration Enhances Removal Efficiency of Pollutants in Constructed Wetlands

Bai

Ding

et al. 2016

Water

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Abstract:This study aimed at optimizing horizontal subsurface flow constructed wetlands (CWs) to improve hydraulic performance and pollutant removal efficiency. A groundwater modeling package (MODFLOW) was used to optimize three design parameters (length-to-width ratio, inlet/outlet-to-length ratio, and substrate size configuration). Using the optimized parameters, three pilot-scale CWs were built to treat actual wastewater. For model validation, we used a tracer test to evaluate hydraulic performance, and investigated the pollutant spatial distributions and removal efficiencies. We conclude that MODFLOW is suitable for designing CWs, accurately predicting that increasing hydraulic conductivity from surface to bottom layers could improve performance. However, the effect of vegetation, which decreased the hydraulic conductivity of the surface layer, should be considered to improve simulation results. Multilayer substrate configuration, with increasing hydraulic conductivity from the surface to bottom layers, significantly increased pollutant removal compared with monolayer configuration. The spatial variation in pollutant transport and degradation through the filling substrate showed that the multilayer configuration was able to increase use of the available space and moderately reduced short-circuiting and dead zones. Thus, multilayer CWs had higher experimental retention times, effective volume fractions and hydraulic efficiencies, and lower short-circuiting compared with monolayer CWs operating under similar conditions.

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Section: Hydraulic Performancesupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Multilayer Substrate Configuration Enhances Removal Efficiency of Pollutants in Constructed Wetlands

Bai

Ding

et al. 2016

Water

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“…The exact reasons are yet known but it might be because, at this stage and depth, the fine but thick plant roots as observed in Fig. 2, attached much more biofilm and SS, which adhered together with the extracellular polymeric substances secreted the biofilm and formed an impermeable layer (Samsó and García 2013) and involved a loss of effective volume (Pedescoll et al 2013). Figure 4b illustrated that the hydraulic conductivity in the planted column was larger than that of the unplanted system across all depths.…”

Section: Before Experimentsmentioning

confidence: 92%

Effects of plant roots on the hydraulic performance during the clogging process in mesocosm vertical flow constructed wetlands

Zhao

Kong

et al. 2014

Environ Sci Pollut Res

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The aim of this study was to evaluate the effects of plant roots (Typha angustifolia roots) on the hydraulic performance during the clogging process from the perspective of time and space distributions in mesocosm vertical flow-constructed wetlands with coarse sand matrix. For this purpose, a pair of lab-scale experiments was conducted to compare planted and unplanted systems by measuring the effective porosity and hydraulic conductivity of the substrate within different operation periods. Furthermore, the flow pattern of the clogging process in the planted and unplanted wetland systems were evaluated by their hydraulic performance (e.g., mean residence time, short circuiting, volumetric efficiency, number of continuously stirred tank reactors, and hydraulic efficiency factor) in salt tracer experiments. The results showed that the flow conditions would change in different clogging stages, which indicated that plants played different roles related to time and space. In the early clogging stages, plant roots restricted the flow of water, while in the middle and later clogging stages, especially the later stage, growing roots opened new pore spaces in the substrate. The roots played an important role in affecting the hydraulic performance in the upper layer (0-30 cm) where the sand matrix had a larger root volume fraction. Finally, the causes of the controversy over plant roots' effects on clogging were discussed. The results helped further understand the effects of plant roots on hydraulic performance during the clogging process.

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“…As the occlusion of interstitial spaces advances, an increase in load loss is observed, especially in the system's initial region, leading to a decrease in Ks and, consequently, surface flow occurrence, with possible decrease in treatment system efficiency (KNOWLES et al, 2011;PEDESCOLL et al, 2013). This possibly makes the hydraulic conductivity a variable with a strong association with porous medium clogging.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Conductivity Variability in Horizontal Subsurface Flow Constructed Wetlands

et al. 2017

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Many modifications in hydrodynamic conditions occur inside the bed of a horizontal subsurface flow constructed wetland (HSSF-CW) in operation. Studies on hydraulic conductivity measurement techniques in HSSF-CW are imperative since the monitoring of flow conditions is essential for understanding and controlling its clogging. This study aimed to assess the hydrodynamic behavior in HSSF-CW by means of saturated hydraulic conductivity (Ks) analysis. For this, six HSSF-CW were used: two non-cultivated (control), two cultivated with Tifton 85 (Cynodon spp.), and two cultivated with alligator weed (Alternanthera philoxeroides). Application of swine wastewater (SW) in HSSF-CW started on June 15, 2011, with Ks measurement period between September 9 and November 11, 2011, in which five measurements were performed in different positions along the system length and over experimental period in order to assess the effects of vegetation, position, and time factors on this variable. Ks values ranged from 1,392 to 2,834 m d −1 . Plant presence led to Ks decreasing in the systems, but cultivated species had no influence on this variable. Monitoring time of HSSF-CW was no longer enough to provide a reduction in Ks, at 10% probability level.

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Design configurations affecting flow pattern and solids accumulation in horizontal free water and subsurface flow constructed wetlands

Cited by 56 publications

References 25 publications

Multilayer Substrate Configuration Enhances Removal Efficiency of Pollutants in Constructed Wetlands

Multilayer Substrate Configuration Enhances Removal Efficiency of Pollutants in Constructed Wetlands

Effects of plant roots on the hydraulic performance during the clogging process in mesocosm vertical flow constructed wetlands

Hydraulic Conductivity Variability in Horizontal Subsurface Flow Constructed Wetlands

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