Transport of bacteria through geologic media

Abstract

A review of the current literature on transport of bacteria through geologic media is presented. The review addresses the major controls on bacterial transport. These controls include the nature of the substratum, the solute, and the bacterial cell. Most knowledge on the transport of bacteria through geologic media has been gained from column studies. There is need for some standardization of approaches, particularly with regard to data collection and controls on factors such as ionic strength and flow velocity. Other systems including glass micromodels have been used in conjunction with microscopy and scanning confocal laser microscopy to examine the controls on transport at the pore scale rather than porous medium scale of column studies. Many inconsistencies exist regarding the effect of the numerous variables that impact bacterial sorption in porous media. These variables include the nature of the substratum (i.e., the presence or absence of coatings), chemical composition of the solute (particularly ionic strength), system hydrodynamics, and bacterial variables such as size, shape, hydrophobicity, and electrostatic charge. Mathematical models based on the advective–dispersion equation have been developed to simulate bacterial transport. Within specific limits, these models can approximate most aspects of bacterial transport; however, they neglect parameters such as growth and behavior of bacteria. There is a need for theoretical development, extensive laboratory investigation, and model development before the goal of prediction of bacterial transport at field scale may be realized.Key words: sorption, advection, dispersion, models, facilitated transport.