Transport and retention of bacteria through a filtration system consisting of sands and geotextiles

Water-saturated column experiments were conducted to study the effect of nonwoven geotextiles on bacteria transport and deposition through two sandy porous media with grain sizes 1.05 and 3.25 mm. The breakthrough curves (BTCs) of tracer for the all porous media exhibited an asymmetrical shape with a substantial tailing, indicating that non-equilibrium and dispersive flow patterns in these porous media. The mass recovery of the bacteria from the effluent (Meff) increased with grain size. The retention profiles (RPs) exhibited hyperexponential behavior, especially in the finer sand. The presence of the geotextiles increased bacteria retention rate. For a given geotextile, greater retention was observed in the surrounding region close to the geotextile. Moreover, the retention of bacteria became more significant in the geotextile with a lower porosity. Results demonstrated that model simulations of bacteria transport and fate need to accurately account for both observed BTC and RP behaviors and also the geotextile placement can impact mechanisms of retention.