Comment on “Transport and fate of bacteria in porous media: Coupled effects of chemical conditions and pore space geometry” by Saeed Torkzaban et al.

Li, Xiqing; Tong, Meiping; Ma, Haihong

doi:10.1029/2008wr007389

Cited by 18 publications

(21 citation statements)

References 21 publications

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“…This method is justified on the basis that there can exist roughness, macromolecules, etc. that may effectively extend surface friction to the attractive secondary well [ Johnson et al ., ].…”

Section: Mechanistic Prediction Of Retention In Favorable and Unfavormentioning

confidence: 99%

Predicting colloid transport through saturated porous media: A critical review

et al. 2015

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Understanding and predicting colloid transport and retention in water‐saturated porous media is important for the protection of human and ecological health. Early applications of colloid transport research before the 1990s included the removal of pathogens in granular drinking water filters. Since then, interest has expanded significantly to include such areas as source zone protection of drinking water systems and injection of nanometals for contaminated site remediation. This review summarizes predictive tools for colloid transport from the pore to field scales. First, we review experimental breakthrough and retention of colloids under favorable and unfavorable colloid/collector interactions (i.e., no significant and significant colloid‐surface repulsion, respectively). Second, we review the continuum‐scale modeling strategies used to describe observed transport behavior. Third, we review the following two components of colloid filtration theory: (i) mechanistic force/torque balance models of pore‐scale colloid trajectories and (ii) approximating correlation equations used to predict colloid retention. The successes and limitations of these approaches for favorable conditions are summarized, as are recent developments to predict colloid retention under the unfavorable conditions particularly relevant to environmental applications. Fourth, we summarize the influences of physical and chemical heterogeneities on colloid transport and avenues for their prediction. Fifth, we review the upscaling of mechanistic model results to rate constants for use in continuum models of colloid behavior at the column and field scales. Overall, this paper clarifies the foundation for existing knowledge of colloid transport and retention, features recent advances in the field, critically assesses where existing approaches are successful and the limits of their application, and highlights outstanding challenges and future research opportunities. These challenges and opportunities include improving mechanistic descriptions, and subsequent correlation equations, for nanoparticle (i.e., Brownian particle) transport through soil, developing mechanistic descriptions of colloid retention in so‐called “unfavorable” conditions via methods such as the “discrete heterogeneity” approach, and employing imaging techniques such as X‐ray tomography to develop realistic expressions for grain topology and mineral distribution that can aid the development of these mechanistic approaches.

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Section: Mechanistic Prediction Of Retention In Favorable and Unfavormentioning

confidence: 99%

Predicting colloid transport through saturated porous media: A critical review

et al. 2015

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“…For example, “cold” colloids have been assumed to be irreversibly associated with the surface, that is, the “cold” fraction is considered equal to α corresponding to genuine attachment to the surface [ Hahn and O'Melia , 2004]. But in fact, “cold” colloids are not immobilized by secondary energy minimum interaction, except under the circumstance where one extends surface friction to the secondary energy minimum and where the resulting torque balance supports immobilization [ Johnson et al ., ]. Shen et al .…”

Section: Existing Upscaling Under Unfavorable Conditions: Two‐region mentioning

confidence: 99%

Upscaling colloid transport and retention under unfavorable conditions: Linking mass transfer to pore and grain topology

Johnson

Hilpert

2013

Water Resour. Res.

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[1] We revisit the classic upscaling approach for predicting Darcy-scale colloid retention based on pore-scale processes, and explore the implicit assumption that retention is a Markov process. Whereas this assumption holds under favorable attachment conditions, it cannot be assumed to hold under unfavorable conditions due to accumulation of colloids in the near-surface fluid domain. We develop a novel link between two-layer mass transfer parameters and the topologies of the pore and collector domains, starting with an elegant outcome of classic colloid filtration theory: that the likelihood of mass transfer from the bulk-to the near-surface fluid domain depends strongly on colloid proximity to the forward flow stagnation axis of each collector (grain). Applying this concept to colloid mass transfer from the near-surface to the bulk fluid domain yields the conclusion that such mass transfer predominantly occurs at rear-flow stagnation zones on collector surfaces. We support this concept with experimental proof that the alignment of rear and forward flow stagnation zones influences colloid mass transfer to surfaces. Colloid accumulation in the near-surface fluid domain under unfavorable conditions may produce extended tailing of colloids during elution in Darcy-scale studies by: (1) long residence times of colloids in the near-surface fluid domain; (2) direct propagation of near-surface colloids from upstream to downstream collectors. The latter generates correlated motion that violates the assumed independence of colloid retention on history of transport. We suggest an approach to upscaling that accounts for the above-described influences of colloid-surface interactions and pore/collector domain topology.Citation: Johnson, W. P., and M. Hilpert (2013), Upscaling colloid transport and retention under unfavorable conditions: Linking mass transfer to pore and grain topology, Water Resour. Res., 49, 5328-5341,

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“…The fluid velocity component in the tangential coordinate ( V ) can be obtained from the stream function using . By further differentiating the aforementioned equation with respect to r , the expression of ∂ V /∂ r is derived as The torque balance analysis regarding initiation of rolling is considered valid only for the colloids that have been immobilized on collector surfaces [ Johnson et al , 2009]. This type of analysis has been widely used for determining the influence of hydrodynamic drag on reentrainment of colloids associated with collectors via primary energy minima [ Johnson and Tong , 2006; Li et al , 2005; Bergendahl and Grasso , 2000, 2003].…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Predicting attachment efficiency of colloid deposition under unfavorable attachment conditions

Shen

Huang

et al. 2010

Water Resources Research

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[1] This study presents an a priori model for predicting attachment efficiency of colloid deposition in porous media under unfavorable conditions. The model takes into account coupled effects of diffusion and hydrodynamic forces on colloid attachment efficiency that result from both primary and secondary minimum deposition. Effect of diffusion was quantified using the Maxwell approach, and influence of hydrodynamic drag was determined by comparing adhesive and hydrodynamic torques that act on the attached colloids. Main findings from this study include (1) the attachment efficiency does not change with increase of flow velocity until it reaches a critical value at which the attachment efficiency decreases as flow velocity further increases and (2) the attachment efficiency increases with increasing collector diameter when the condition that adhesive torque is greater than hydrodynamic torque is not guaranteed over the entire collector surface. Whereas the classic filtration theory only takes into account the effects of system hydrodynamics on single collector contact efficiency, we show additionally their effects on attachment efficiency. Furthermore, results of this study imply that in addition to the important role that collector size plays in the straining process, which has been the focus of many recent studies, it also influences the attachment process thus must be considered when describing colloid retention and transport in porous media under unfavorable attachment conditions.

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Comment on “Transport and fate of bacteria in porous media: Coupled effects of chemical conditions and pore space geometry” by Saeed Torkzaban et al.

Cited by 18 publications

References 21 publications

Predicting colloid transport through saturated porous media: A critical review

Predicting colloid transport through saturated porous media: A critical review

Upscaling colloid transport and retention under unfavorable conditions: Linking mass transfer to pore and grain topology

Predicting attachment efficiency of colloid deposition under unfavorable attachment conditions

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