Differential pressure transducer to understand the behaviour in the gaseous and hydraulic phases of infiltration-percolation systems and their applicability to vertical-flow wetlands | Mesure de pression differentielle pour comprendre le comportement des phases gazeuse et hydraulique des systèmes d'infiltration percolation et application pour les filtres plantés de roseaux

[Departement_IRSTEA]MA [TR1_IRSTEA]TED / EPURE

anglais. Within the scope of studying the hydraulic behaviour of vertical-flow wetland in order to model these systems, differential pressure transducers were used on experimental vertical sand columns to understand the effects of a batch feed on the gaseous and hydraulic phases. Three transducers were set up at three different depths in the column. The system operates in a batch mode. Two types of flow regime were tested. The first one consists of one batch of 10 litres every 8 hours. In this regime, the transducer signal shows four consecutive phases: the influence of the water head on the top of the filter and the infiltration of the batch inside the filter that both increase the pressure, the drainage of the pores that decrease the pressure to a depression and finally the aeration of the pores that restore the pressure to atmospheric pressure. For the second flow regime (a batch of 4 litres every 3 hours) the same consecutive steps are present except the infiltration of the batch. In addition, the drainage and the aeration of the pores are simultaneous over the entire depth of the column and are incidental to the end of the surface dewatering. This is not the case for the first regime where occurrence of those steps depends on the depth. In addition to the understanding of the different steps occurring when a batch volume percolates, those measurements provide useful information on the saturation of the media, the rate of drainage and aeration of the pore, the gas flow, the infiltration rate.