Transport of E. coli in Presence of Naturally Occuring Colloids in Saturated Porous Media

Abstract

This study focuses on the effects of organic (humic acid substances) and inorganic (bentonite clay, silicate, and kaolinite clay) colloids on the transport of bacteria under saturated flow conditions. The transport experiments of Escherichia coli were performed in 40-cm long column filled with river sand of diameter 400 μm. Batch sorption experiments were conducted to understand the attachment kinetics of bacteria in the presence of humic acid and clay colloids. Humic acid was found to enhance the transport of bacteria by 17.3% in the presence of NaCl and by 10.3% in the presence of CaCl2 while clay colloids were found to reduce the transport. The transport of bacteria decreased by 11.8, 33.8, and 67% (in the presence of NaCl) and by 58.8, 41.18, and 76.5% (in the presence of CaCl2) with bentonite clay, silicate, and kaolinite clay colloids, respectively. The addition of divalent ion enhanced the complexity leading to the formation of complexes thereby reducing the transport. The combined existence of these colloids, the water chemistry, and the chemical composition of the colloids could govern the interaction processes in the subsurface matrix and can hence influence the transport of biocolloids in the environment significantly.