Rôle de paramètres opérationnels et des substances organiques dans la structure physique des dépôts de surface des filtres plantés de roseaux à écoulement vertical

Abstract : In the so-called "classical French system" of constructed wetlands, the percolation through the filter medium of untreated raw wastewater results in the accumulation of sludge deposits which gradually forms a sludge layer mainly on the surface of the first filter stage. The structure, composition and organization of the particulate matter of the deposits are determining factors of the macroscopic properties of the sludge layer, such as permeability, oxygen transfer, etc. In this study, representative samples of surface deposits were collected from 12 French vertical flow constructed wetlands (VFCW) in operation. The results of analyzes showed a remarkable similarity of their particle size distribution, and a relatively moderate but significant aggregation. The differences in operational conditions between the 12 selected treatment plants (age, implementation of additional treatments), did not have any observable effect on the particle size distribution in the sludge deposits. It was also observed that particle size and agregation were not related to the content of microbial exocellular polymeric substances (EPS). These substances were analyzed in surface deposits at much lower levels than in activated sludges for example, in which their role in the formation of microbial flocs is well documented in the scientific literature. On the other hand, humic substances were analyzed at much higher levels in sludge deposits, suggesting that the contribution of humic substances to the aggregation processes was greater than that of the analyzed EPSs. The environmental conditions of surface deposits on filters planted with reeds thus induce aging processes similar to those observed in neosols.
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Manon Kania, Mathieu Gautier, Ségolène Loupiac, Philippe Michel, Rémy Gourdon. Rôle de paramètres opérationnels et des substances organiques dans la structure physique des dépôts de surface des filtres plantés de roseaux à écoulement vertical. Déchets, Sciences et Techniques, 2018, 77 (N°77), pp.43-57. ⟨10.4267/dechets-sciences-techniques.3808⟩. ⟨hal-02045336⟩

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