MODELAGEM MATEMÁTICA PARA APLICAÇÃO DE SISTEMAS DE WETLANDS NO TRATAMENTO DE AQÜÍFEROS LIVRES E RASOS CONTAMINADOS

Wetlands are habitats where water level can be either above, beneath or at surface ground. Swamp and marsh are examples of natural wetlands. However, there are also the manmade ones, generally constructed for environmental purposes. Using Visual Modflow were created four possible wetlands application scenarios for the contaminant plume attenuation in shallow aquifers, without pumping (natural gradient). Three of them, representing superficial flow systems, were compared one each other, varying window water entrance geometry and depth in the contaminant plume capture and recharge. Results indicate that water volume that enters into the wetland varies inversely with the water residence time in the channel and both are controlled by aquifer hydraulic conductivity. In simulations using 250 mm/y of recharge, the residence time was smaller than the ones obtained with no recharge simulations. The horizontal dimension of captured plume can be enlarged with the building up of an impermeable funnel barrier in the entrance of the wetland, used to enlarge wetland permeable entrance. However, inserting vertical barriers, at least 4 m below the wetland entrance, the results were not so effective. A forth model, representing a shallow wetland followed by a shallow flow system, required a 200 m 2 area to treat 16m 3 /day. Modeling results indicated viability of groundwater treatment using wetlands, although, large areas are required to have an effective groundwater plume remediation.