Wetland systems for water pollution control.
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Abstract
: This study aims at defining a methodology to evaluate K s reductions of gravel material constituting CW bed 11 matrices. Several schemes and equations for the Lefranc’s test were compared by using different gravel sizes and at 12 multiple spatial scales. The falling-head test method was implemented by using two steel permeameters one impervious 13 (IMP) and one pervious (P) on one side. At laboratory scale, mean K values for a small size gravel (8-15 x 10 -2 m) 14 measured by the IMP and the P permeameters were equal to 19466 m/d and 30662 m/d, respectively. Mean K s values for a 15 big size gravel (10-25 x 10 -2 m) measured by the IMP and the P permeameters were equal to 12135 m/d and 20866 m/d, 16 respectively. Comparison of K s values obtained by the two permeameters at lab scale as well as a sensitivity analysis and a 17 calibration, lead to the modification of the standpipe equation, to evaluate also the temporal variation of the horizontal K s . 18 In particular, both permeameters allow the evaluation of the K s decreasing after 4 years-operation and 1-1.5 years-operation 19 of the plants at full scale (filled with the small size gravel) and at pilot scale (filled with the big size gravel) respectively.