A brief review of bacterial transport in natural porous media

Ginn, Timothy R.

doi:10.2172/197807

Cited by 7 publications

(6 citation statements)

References 72 publications

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“…Electrostatic forces also play an important role in the distribution (and mobility) of colloids. Anionic colloids will be excluded from locations adjacent to negatively charged solid surfaces; similar to the much reported anion exclusion process for anionic solutes (Krupp, 1972;Gvirtzman and Gorelick, 1991;Ginn, 1995). In case of size or anion exclusion, colloids will tend to reside in larger pores and in more conductive parts of the flow domain.…”

mentioning

confidence: 65%

Colloid‐Facilitated Solute Transport in Variably Saturated Porous Media: Numerical Model and Experimental Verification

Šimůnek

Pang

et al. 2006

Vadose Zone Journal

153

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Strongly sorbing chemicals (e.g., heavy metals, radionuclides, pharmaceuticals, and explosives) in porous media are associated predominantly with the solid phase, which is commonly assumed to be stationary. However, recent field‐ and laboratory‐scale observations have shown that in the presence of mobile colloidal particles (e.g., microbes, humic substances, clays, and metal oxides), colloids can act as pollutant carriers and thus provide a rapid transport pathway for strongly sorbing contaminants. To address this problem, we developed a one‐dimensional numerical model based on the HYDRUS‐1D software package that incorporates mechanisms associated with colloid and colloid‐facilitated solute transport in variably saturated porous media. The model accounts for transient variably saturated water flow, and for both colloid and solute movement due to advection, diffusion, and dispersion, as well as for solute movement facilitated by colloid transport. The colloid transport module additionally considers the processes of attachment/detachment to/from the solid phase and/or the air–water interface, straining, and/or size exclusion. Various blocking and depth dependent functions can be used to modify the attachment and straining coefficients. The solute transport module uses the concept of two‐site sorption to describe nonequilibrium adsorption–desorption reactions to the solid phase. The module further assumes that contaminants can be sorbed onto surfaces of both deposited and mobile colloids, fully accounting for the dynamics of colloid movement between different phases. Application of the model is demonstrated using selected experimental data from published saturated column experiments, conducted to investigate the transport of Cd in the presence of Bacillus subtilis spores in alluvial gravel aquifer media. Numerical results simulating bacteria transport, as well as the bacteria‐facilitated Cd transport, are compared with experimental results. A sensitivity analysis of the model to various parameters is also presented.

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mentioning

confidence: 65%

Colloid‐Facilitated Solute Transport in Variably Saturated Porous Media: Numerical Model and Experimental Verification

Šimůnek

Pang

et al. 2006

Vadose Zone Journal

153

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“…Early breakthrough of microorganisms compared to that of conservative tracer has also been observed or predicted [e.g., Powelson et al , 1993; Bales et al , 1989; Ginn , 1995]. Stochastic analysis of virus transport in aquifers show that increasing heterogeneity in the model results in faster breakthrough of 0.02–0.2 μm colloids [ Rehmann et al , 2000].…”

Section: Introductionmentioning

confidence: 90%

Transport of colloids in saturated porous media: A pore‐scale observation of the size exclusion effect and colloid acceleration

Sirivithayapakorn

Keller

2003

Water Resources Research

168

128

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[1] We present experimental evidence of the effect of colloid exclusion from areas of small aperture sizes, using direct observations at the pore-scale using a realistic micromodel of porous media. Four sizes of hydrophobic latex spheres in aqueous suspension, from 0.05 to 3 mm, were introduced into the micromodel at three different pressure gradients. We observed the frequency of occurrence of the size exclusion effect and the influence of relative size of pore throats and colloids (T/C ratio) and flow velocity. From our observations the smallest T/C ratio entered by these different colloids was 1.5. We also observed certain preferential pathways through the pore space for different colloid sizes, such that size exclusion eventually results in distinct pathways. These preferential paths become more important for larger colloids and for greater pressure gradients. Measured colloid velocities were 4-5.5 times greater than estimated pore water velocities. Acceleration factors (ratio of colloid to water velocity) increased for all colloid sizes with increasing pore-scale Pe. Smaller particles appeared to travel along faster streamlines in pore throats, while larger particles travel along with a number of streamlines, thus at a slightly lower velocity than the small colloids. At larger scales the acceleration factor is decreased owing to Brownian motion, adsorption, colloid and straining filtration, and other factors, but these pore-scale results shed light on the size exclusion effect and its role in determining early colloid breakthrough.

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“…To date, there have been several informative review papers on the transport behaviors of NP [e.g., 12,22,23,47,48,88,[112][113][114] and other colloids [e.g., 30,36,53,68,98,100,[115][116][117][118][119][120][121].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…115, 283, 285, 297-300]. Second, at pore scale size exclusion has been attributed to migration of particles on flow paths which are close to the center of the pore channels where the velocity is theoretically 1.5 times larger than the mean pore water velocity-similar to the phenomena in solute transport context called "charge" or "anion exclusion", but with different underlying forces [58,116,139,151,153,283].…”

Section: Mechanismmentioning

confidence: 99%

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review

Babakhani¹,

Bridge

Doong³

et al. 2017

Advances in Colloid and Interface Science

136

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Environmental applications of nanoparticles (NP) increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena. This review aims to describe consistently all the important NP transport mechanisms along with their representative mathematical continuum models as found in the current scientific literature. Detailed characterizations of each transport phenomenon in regards to their manifestation in the column experiment outcomes, i.e., breakthrough curve (BTC) and residual concentration profile (RCP), are presented to facilitate future interpretations of BTCs and RCPs. The review highlights two NP transport mechanisms, agglomeration and size exclusion, which are potentially of great importance in controlling the fate and transport of NP in the subsurface media yet have been widely neglected in many existing modeling studies. A critical limitation of the continuum modeling approach is the number of parameters used upon application to larger scales and when a series of transport mechanisms are involved. We investigate the use of simplifying assumptions, such as the equilibrium assumption, in modeling the attachment/detachment mechanisms within a continuum modelling framework. While acknowledging criticisms about the use of this assumption for NP deposition on a mechanistic (process) basis, we found that its use as a description of dynamic deposition behavior in a continuum model yields broadly similar results to those arising from a kinetic model. Furthermore, we show that in two dimensional (2-D) continuum models the modeling efficiency based on the Akaike information criterion (AIC) is enhanced for equilibrium vs kinetic with no significant reduction in model performance. This is because fewer parameters are needed for the equilibrium model compared to the kinetic model. Two major transport regimes are identified in the transport of NP within porous media. The first regime is characterized by higher particle-surface attachment affinity than particle-particle attachment affinity, and operat...

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A brief review of bacterial transport in natural porous media

Cited by 7 publications

References 72 publications

Colloid‐Facilitated Solute Transport in Variably Saturated Porous Media: Numerical Model and Experimental Verification

Colloid‐Facilitated Solute Transport in Variably Saturated Porous Media: Numerical Model and Experimental Verification

Transport of colloids in saturated porous media: A pore‐scale observation of the size exclusion effect and colloid acceleration

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review

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