Caracterizing hydraulic properties of filter material of a vertical flow constructed wetland

Morvannou, Ania [IRSTEA, Villeurbanne, France] Forquet, Nicolas [IRSTEA, Villeurbanne, France] Vanclooster, Marnik [UCL] Molle, Pascal [IRSTEA, Villeurbanne, France]

Characterizing the hydraulic properties of filter material used in a vertical flow constructed wetland(VFCW) is a prerequisite to model wastewater treatment using process-based models. The filter materialis a matrix of porous mineral material and organic matter that makes hydraulic characterization a difficulttask. Here, we present a combined laboratory and in situ approach to assess the hydraulic properties of aVFCW installed at Evieu in Ain, France. The laboratory approach produces prior estimates of the local prop-erties of the different VFCW system layers. These prior estimates are subsequently refined with inverselyestimated parameters using the HYDRUS-1D code in combination with in situ hydrodynamic measure-ments. Laboratory experiments consisted of both direct (sand box, pressure chamber, and permeameterexperiments) and inverse estimates (evaporation method) of hydraulic parameters. In situ measurementswere based on 5.5-day monitoring of the full-scale filter using 24 time domain reflectometry (TDR) probesinstalled at different depths. Applying the methodology with successive optimizations led to a reliableassessment of the hydraulic parameters of the VFCW. We conclude that the consistent representation ofthe hydraulic behavior of the VFCW requires in situ hydrodynamic observations combined with inversemodeling. However, to avoid the ill-posedness of the inverse problem, the number of fitted parametersshould be kept to a minimum and parameter initialization need to be based on local-scale laboratorymeasurements.