Modeling microbial transport in porous media: Traditional approaches and recent developments (original) (raw)
Related papers
Transport and fate of microorganisms in porous media: A theoretical investigation
Journal of Hydrology, 1984
Bacteria and viruses found in groundwater are a proven health hazard as evidenced by the large number of outbreaks of water-borne diseases caused by contaminated groundwater. To analyze the fate of biological contaminants in soils and groundwater, we studied various transport processes including dispersion, convection, Brownian motion, chemotaxis and tumbling of bacteria. The differences between bacteria and viruses in their transport mechanisms, decay and growth kinetics have also been investigated. It has been shown that the rate of deposition terms can be incorporated by a first-order and an adsorption isotherm for bacteria and viruses, respectively. The movement of bacteria is coupled with the transport of a bacterial nutrient present in seeping wastewater.
Transport of bacteria in an aquifer sand: Experiments and model simulations
Water Resources Research, 1994
Experiments were carried out to determine the breakthrough of bacteria through a saturated aquifer sand at three flow velocities and three cell concentrations. Bacteria were either suspended in deionized water or 0.01 mol L -• NaCI solution. Bacterial transport was found to increase with flow velocity and cell concentration but was significantly retarded in the presence of 0.01 mol L -• NaC1. A mathematical model based on the advection-dispersion equation was formulated to describe bacterial transport and retention in porous media. The transport equations for bacteria were solved using the finite difference Crank-Nicolson scheme combined with Newton-Raphson iterations. The best fit of the numerical model to the experimental data was obtained using the downhill simplex optimization technique to minimize the sum of the squares of deviations between model predictions and experimental data by varying three parameters. This numerical model was found to describe the experimental data very well under all the experimental conditions tested. An alternative model (also based on the advection-dispersion equation) was tested against all the experimental data sets, but it did not represent the experimental data as well as the model proposed in this paper. face materials [e.g., Bitton et al., 1974; Wollum and Cassel, 1978; Smith et al., 1985; Parke et al., !986; Tan et al., 1991]. Many environmental factors such as ionic strength and flow velocity of the soil solution and properties of the porous materials have been identified to affect microbial transport in porous media in qualitative terms [e.g., Goldshrnid et al., 1973; Bitton et al., !974; Smith et al., !978; Wollum and Cassel, 1978; Gerba and Bitton, !984; McDowell-Boyer et al., 1986; Fontes et al., 1991; Gannon et al., 1991b; Gammack et al., 1992]. Complex mathematical models have also been developed to describe bacterial transport in porous media [e.g., Corapcioglu and Haridas, 1984, !985; Taylor and Jaffe, 1990]. Despite the experimental and modeling 1Now at Centre for Environmental Mechanics, CSIRO, Canben'a, Australia.
Fate of microorganisms in porous media has very important applications in many branches of environmental and petroleum science and engineering, among others; however, concurrently it is a very complex and interacting phenomenon mainly because microorganisms are living. Applying the systematic modeling approach to continuum systems, we derive a model that include net flux of microorganisms and nutrients by convection and dispersion, growth and decay rates of microorganisms, chemotactic movement and nutrient consumption, adsorption of microorganisms and nutrients on rock grain surfaces, as well as desorption of microorganisms. Porosity reduction due to cell adsorption is considered. We use the Solute Transport application of the Earth Science Module in COMSOL Multiphysics to implement a numerical solution of the model. The numerical simulations reproduce results previously reported elsewhere; moreover, we show the spatial-temporal distribution of microorganisms and nutrients along the system and time. We point out the complementary role of the spatial-temporal distribution of components with breakthrough curves to analyze the behavior of both fluent and adsorbed components.
Modeling Microbial Transport and Biodegradation in a Dual-porosity System
1999
A mathematical model describing microbial transport and growth in a heterogeneous aquifer domain, composed of overlapping subdomains of high-permeability and low-permeability materials, is developed. Each material is conceptually visualized as a continuum which occupies the entire considered spatial aquifer domain. Based on the assumption that advection in the lowpermeability domain is negligible, the mathematical model is solved by using a publically available reactive transport code. The importance of modeling microbial transport and growth in such a dual-porosity system is demonstrated through a hypothetical case study.
Journal of Contaminant Hydrology, 2005
This paper evaluates the importance of seven types of parameters to virus transport: hydraulic conductivity, porosity, dispersivity, sorption rate and distribution coefficient (representing physical-chemical filtration), and in-solution and adsorbed inactivation (representing virus inactivation). The first three parameters relate to subsurface transport in general while the last four, the sorption rate, distribution coefficient, and in-solution and adsorbed inactivation rates, represent the interaction of viruses with the porous medium and their ability to persist. The importance of four types of observations to estimate the virus-transport parameters are evaluated: hydraulic heads, flow, temporal moments of conservative-transport concentrations, and virus concentrations. The evaluations are conducted using one-and two-dimensional homogeneous simulations, designed from published field experiments, and recently developed sensitivity-analysis methods. Sensitivity to the transport-simulation time-step size is used to evaluate the importance of numerical solution difficulties. Results suggest that hydraulic conductivity, porosity, and sorption are most important to virus-transport predictions. Most observation types provide substantial information about hydraulic conductivity and porosity; only virus-concentration observations provide information about sorption and inactivation. The observations are not sufficient to estimate these important parameters uniquely. Even with all observation types, there is extreme parameter correlation between porosity and hydraulic conductivity and between the sorption rate and in-0169-7722/$ -see front matter. Published by Elsevier B.V. solution inactivation. Parameter estimation was accomplished by fixing values of porosity and insolution inactivation. Published by Elsevier B.V.
Physical and chemical factors influencing transport of microorganisms through porous media
Applied and Environmental Microbiology, 1991
Resting-cell suspensions of bacteria isolated from groundwater were added as a pulse to the tops of columns of clean quartz sand. An artificial groundwater solution (AGW) was pumped through the columns, and bacterial breakthrough curves were established and compared to test the effects of ionic strength of the AGW, cell size (by using strains of similar cell surface hydrophobicity but different size), mineral grain size, and presence of heterogeneities within the porous media on transport of the bacteria. The proportion of cells recovered in the effluent ranged from nearly 90% for AGW of a higher ionic strength (I = 0.0089 versus 0.00089 m), small cells (0.75-micron-diameter spheres versus 0.75 by 1.8-micron rods), and coarse-grained sand (1.0 versus 0.33 mm) to less than 1% for AGW of lower ionic strength, large cells, and fine-grained sand. Differences in the widths of peaks (an indicator of dispersion) were significant only for the cell size treatment. For treatments containing h...
The mechanistic aspects of microbial transport in porous media
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Water Resources Research, 2008
1] Experimental and theoretical studies were undertaken to explore the coupled effects of chemical conditions and pore space geometry on bacteria transport in porous media. The retention of Escherichia coli D21g was investigated in a series of batch and column experiments with solutions of different ionic strength (IS) and ultrapure quartz sand. Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations and results from batch experiments suggested that bacteria attachment to the sand surface was negligible when the IS was less than or equal to 50 mM. Breakthrough data from column experiments showed significant cell retention and was strongly dependent on the IS. This finding indicates that cell retention was dependent on the depth of the secondary energy minimum which increases with IS. When the IS of the influent bacteria-free solution was decreased to 1 mM, only a small fraction of the retained bacteria was released from the column. The remaining retained bacteria, however, were recovered from the sand, which was excavated from the column and suspended in a cell-free electrolyte having the original IS. These observations suggest that the solution chemistry is not the only parameter controlling bacteria retention in the porous media. Computational simulations of flow around several collector grains revealed the retention mechanism, which is dependent on both the solution chemistry and the pore space geometry. Simulations demonstrate that the pore space geometry creates hydrodynamically disconnected regions. The number of bacterial cells that may be transported to these relatively ''immobile'' regions will theoretically be dependent on the depth of the secondary energy minimum (i.e., the IS). Once bacteria are trapped in these immobile regions, reduction of the secondary energy minimum does not necessarily release the cells owing to hydrodynamic constraints. Citation: Torkzaban, S., S. S. Tazehkand, S. L. Walker, and S. A. Bradford (2008), Transport and fate of bacteria in porous media: Coupled effects of chemical conditions and pore space geometry, Water Resour. Res., 44, W04403,
A Mathematical Model for Transport and Growth of Microbes in Unsaturated Porous Soil
Mathematical Problems in Engineering
In this work, we develop a mathematical model for transport and growth of microbes by natural (rain) water infiltration and flow through unsaturated porous soil along the vertical direction under gravity and capillarity by coupling a system of advection diffusion equations (for concentration of microbes and their growth-limiting substrate) with the Richards equation. The model takes into consideration several major physical, chemical, and biological mechanisms. The resulting coupled system of PDEs together with their boundary conditions is highly nonlinear and complicated to solve analytically. We present both a partial analytic approach towards solving the nonlinear system and finding the main type of dynamics of microbes, and a full-scale numerical simulation. Following the auxiliary equation method for nonlinear reaction-diffusion equations, we obtain a closed form traveling wave solution for the Richards equation. Using the propagating front solution for the pressure head, we re...