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Article

Structural Changes in French VF Treatment Wetland Porous Media during the Rest Period: An Ex Situ Study Using X-ray Tomography

1
Institut Blaise Pascal, 4 Avenue Blaise Pascal TSA 60026/CS 60026, CEDEX, 63178 Aubière, France
2
CNRS, IRD, Grenoble INP, IGE, Université Grenoble Alpes, 38000 Grenoble, France
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INSA-Lyon, MATEIS Laboratory, University of Lyon, UMR CNRS 5510, 20 Avenue Albert Einstein, CEDEX, 69621 Villeurbanne, France
4
UR REVERSAAL, INRAE 5 rue de la Doua-CS70077, 69626 Villeurbanne, France
*
Author to whom correspondence should be addressed.
Academic Editor: Paola Verlicchi
Water 2021, 13(3), 389; https://doi.org/10.3390/w13030389
Received: 4 December 2020 / Revised: 27 January 2021 / Accepted: 27 January 2021 / Published: 2 February 2021
(This article belongs to the Section Wastewater Treatment and Reuse)
Clogging constitutes a major operational issue for treatment wetlands. The rest period is a key feature of French Vertical Flow (VF) treatment wetlands and serves to mitigate clogging. An ex-situ drying experiment was performed to mimic the rest period and record structural changes in the porous media using X-ray Computed Tomography (CT). Samples containing the deposit and gravel layers of a first stage French VF treatment wetland were extracted and left to dry in a control environment. Based on CT scans, three phases were identified (voids, biosolids, and gravels). The impact of the rest period was assessed by means of different pore-scale variables. Ultimately, the volume of biosolids had reduced to 58% of its initial value, the deposit layer thickness dropped to 68% of its initial value, and the void/biosolid specific surface area ratio increased from a minimum value of 1.1 to a maximum of 4.2. Cracks greater than 3 mm developed at the uppermost part of the deposit layer, while, in the gravel layer, the rise in void volume corresponds to pores smaller than 2 mm in diameter. Lastly, the air-filled microporosity is estimated to have increased by 0.11 v/v. View Full-Text
Keywords: constructed wetlands; drying; 3D-phase distribution; clogging constructed wetlands; drying; 3D-phase distribution; clogging
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MDPI and ACS Style

Martinez-Carvajal, G.D.; Oxarango, L.; Adrien, J.; Molle, P.; Forquet, N. Structural Changes in French VF Treatment Wetland Porous Media during the Rest Period: An Ex Situ Study Using X-ray Tomography. Water 2021, 13, 389. https://doi.org/10.3390/w13030389

AMA Style

Martinez-Carvajal GD, Oxarango L, Adrien J, Molle P, Forquet N. Structural Changes in French VF Treatment Wetland Porous Media during the Rest Period: An Ex Situ Study Using X-ray Tomography. Water. 2021; 13(3):389. https://doi.org/10.3390/w13030389

Chicago/Turabian Style

Martinez-Carvajal, German D., Laurent Oxarango, Jérôme Adrien, Pascal Molle, and Nicolas Forquet. 2021. "Structural Changes in French VF Treatment Wetland Porous Media during the Rest Period: An Ex Situ Study Using X-ray Tomography" Water 13, no. 3: 389. https://doi.org/10.3390/w13030389

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