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

Clogging constitutes a major operational issue for treatment wetlands. The rest period is key feature of French Vertical Flow (VF) wetlands and serves to mitigate clogging. An ex-situ drying experiment was performed mimic the record structural changes in porous media using X-ray Computed Tomography (CT). Samples containing deposit gravel layers first stage VF wetland were extracted left dry control environment. Based on CT scans, three phases identified (voids, biosolids, gravels). impact assessed by means different pore-scale variables. Ultimately, volume biosolids had reduced 58% its initial value, layer thickness dropped 68% void/biosolid specific surface area ratio increased from minimum value 1.1 maximum 4.2. Cracks greater than 3 mm developed at uppermost part layer, while, rise void corresponds pores smaller 2 diameter. Lastly, air-filled microporosity estimated have 0.11 v/v.