Transport of colloids through porous beds in the presence of natural organic matter

In this paper we report the effect of concentration of George-Town natural organic matter (GT-NOM) on the transport of latex particles through packed beds of highly purified Ottawa sand. Two types of 2.5 mu m-diameter polystyrene latex, with radically different surface functional groups (amidine and sulfate) were used. Concentrations of the GT-NOM used to equilibrate the porous medium as well as the surface of latex particles varied from zero to 20.0 mg l(-1). Particle breakthrough curves and experimental attachment efficiencies are presented. Results indicate that electrostatic repulsion due to the presence of GT-NOM imparts stability to the particles, thereby decreasing particle attachment in the porous-bed matrix. At the highest GT-NOM concentration, the amidine latex shows a twofold decrease in attachment efficiency, suggesting that steric effects also play a key role in the stability of the particles. (C) 1998 Elsevier Science B.V. All rights reserved.