Effect of a nonwoven geotextile on solute and colloid transport in porous media under both saturated and unsaturated conditions

Geotextiles are thin polymeric materials widely used in geotechnical, environmental and hydraulic applications. They are employed in infiltration basins designed to collect and improve the quality of storm and runoff waters before their infiltration into the surrounding soil. The introduction of geotextiles in the subsoil of infiltration basins may significantly influence the flow and transfer of pollutants present in storm and runoff waters in solute form or associated with colloidal and particulate phases. The objective of this work was to study the influence of a nonwoven geotextile on conservative solute and colloidal transport through sandy and gravel porous media under both saturated and unsaturated conditions. Solute and colloid transport through columns containing soil amended with a geotextile were characterized by injecting a tracer solution and a suspension of colloidal particles at a constant flow rate under saturated and unsaturated conditions. The flow pattern was described using a MIM model implemented with the HYDRUS 1D code. The results showed that nonwoven geotextiles can increase flow homogeneity. Their effect on flow homogenization depended on soil heterogeneity and the degree of water saturation. Colloidal retention efficiency at column scale was also modified by the presence of geotextiles. By homogenizing flow they increased the filter capacity of the soil, thereby decreasing the pollutant transfer in colloidal form.