Transport of bacteria in aquifer sediment: experiments and modeling

A mathematical model based on the advection-dispersion equation, modified to account for growth, decay, attachment, and detachment of microorganisms, was developed to describe the transport and growth of bacteria in aquifers. Column experiments on the transport of a species of sulfate-reducing bacteria through saturated-aquifer sediment were conducted to gain a quantitative knowledge of the attachment and detachment processes. Relevant parameter values such as the attachment-site capacity of the sediment and the attachment and detachment coefficients under different conditions, were obtained by fitting the experimental data with the non-growth condition transport model. The transport model was then refined and improved to incorporate the microbial sulfate reduction mechanism. To evaluate the applicability of this model, bacterial transport in aquifers under both nutrient-rich and oligotrophic environments was modeled by employing the parameters gained from experiments and from available literature; the model results were consistent with observations reported in former studies. In addition, the results revealed that the distribution of bacteria in the aqueous phase and in the sediments is directly related to the attachment-site capacity of the sediment. Thus, the attachment-site capacity of the sediment is a key factor to evaluate the transport and growth of bacteria in aquifers.