Assessment of clogging in constructed wetlands by saturated hydraulic conductivity measurements

Field-based saturated hydraulic conductivity (Ks) measurements can be considered as an indirect method to detect the degree of porous medium clogging in CWs. Ks measurements can be conducted under falling head ponded conditions specifically developed to detect the potentially high water flow of wetland gravels. Anyway, these methods need further validation tests. Therefore, this study aims at defining a methodology to evaluate Ks reduction of gravel material constituting CW bed matrices. In order to meet the aim, several schemes and equations for the Lefranc’s test were compared by using different gravel sizes and at multiple spatial scales (tank, pilot and full plant). In order to apply the falling-head test method, two steel permeameters were implemented, one not perforated and one perforated on one side, connected to a plastic tube by a bulbe valve. Comparison of Ks values obtained by the two permeameters at lab scale with two different size of clean gravel, as well as a sensitivity analysis and a calibration, leaded the modification of the standpipe equation, to evaluate also temporal variation of horizontal Ks.