Use of geotextiles to regulate flow and reduce pollutant transfer in stormwater management

This paper aims at presenting an ensemble of laboratory studies that were performed in two laboratories of the French ministry of public works. The impact of geotextiles on flow and pollutant transfer (reactive solutes but also colloidal particles) was investigated at the laboratory scale. Leaching column experiments were performed to proceed to the successive injection of non reactive solutes to characterize flow processes, of heavy metals as reactive solutes and of latex particles as colloids. The transfers were investigated under several kind of hydric conditions (saturated versus unsaturated) and through several kind of porous media (calcareous deposit, sandy soil and porous gravel). Numerical modeling helped in understanding the geotextile effect on flow and pollutant transfer. All results point at the following assumptions. The geotextiles do not directly remove pollutants or colloids. They help in homogenizing flow through cutting preferential pathways. Through their influence on flow, they improve the contact between pollutants and the reactive matrix and increase the contact time between particles and pollutants. They can be considered as a potential tool for the optimization of pollutant removal in stormwater treatment plants