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Journal ArticleDOI

Transport of Cryptosporidium Oocysts in Porous Media: Role of Straining and Physicochemical Filtration

09 Sep 2004-Environmental Science & Technology (American Chemical Society)-Vol. 38, Iss: 22, pp 5932-5938
TL;DR: The results of this study indicate that irregularity of sand grain shape contributes considerably to the straining potential of the porous medium, and both straining and physicochemical filtration are expected to control the removal of C. parvum oocysts in settings typical of riverbank filTration, soil infiltration, and slow sand filtrations.
Abstract: The transport and filtration behavior of Cryptosporidium parvum oocysts in columns packed with quartz sand was systematically examined under repulsive electrostatic conditions. An increase in solution ionic strength resulted in greater oocyst deposition rates despite theoretical predictions of a significant electrostatic energy barrier to deposition. Relatively high deposition rates obtained with both oocysts and polystyrene latex particles of comparable size at low ionic strength (1 mM) suggest that a physical mechanism may play a key role in oocyst removal. Supporting experiments conducted with latex particles of varying sizes, under very low ionic strength conditions where physicochemical filtration is negligible, clearly indicated that physical straining is an important capture mechanism. The results of this study indicate that irregularity of sand grain shape (verified by SEM imaging) contributes considerably to the straining potential of the porous medium. Hence, both straining and physicochemical filtration are expected to control the removal of C. parvum oocysts in settings typical of riverbank filtration, soil infiltration, and slow sand filtration. Because classic colloid filtration theory does not account for removal by straining, these observations have important implications with respect to predictions of oocyst transport.
Citations
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Journal ArticleDOI
TL;DR: In this article, a review combines patchwise ENM research using natural soils with the much wider literature on ENM performed in standard tests or on the fate of colloids in soils, and an analysis of diverse ENM characteristics determining availability from the soil organisms' perspective to assess the main soil characteristics that determine the fate, speciation, and ultimately bioavailability of ENM in natural soils.
Abstract: Interactions within natural soils have often been neglected when assessing fate and bioavailability of engineered nanomaterials (ENM) in soils. This review combines patchwise ENM research using natural soils with the much wider literature on ENM performed in standard tests or on the fate of colloids in soils, and an analysis of the diverse ENM characteristics determining availability from the soil organisms’ perspective to assess the main soil characteristics that determine the fate, speciation, and ultimately bioavailability of ENM in natural soils. Predominantly salinity, texture, pH, concentration, and nature of mobile organic compounds and degree of saturation determine ENM bioavailability.

355 citations


Cites background from "Transport of Cryptosporidium Oocyst..."

  • ...Straining, Size Exclusion, and Transport in Unsaturated Soils When high removal of ENM is observed in soil columns despite high elektrokinetic barriers normally preventing deposition, straining is often suggested, a process that involves physical entrainment of particles independent of solution chemistry (process 8 in Figure 1; Bradford et al., 2005; Bradford et al., 2003; Tufenkji et al., 2004)....

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  • ...…soil columns despite high elektrokinetic barriers normally preventing deposition, straining is often suggested, a process that involves physical entrainment of particles independent of solution chemistry (process 8 in Figure 1; Bradford et al., 2005; Bradford et al., 2003; Tufenkji et al., 2004)....

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  • ...…only below a particle size to average grain diameter ratio of 0.02 (Bradford et al., 2003), it is believed to occur at lower ratios also because of the roughness of soil particles (Tufenkji et al., 2004) or because ENM gain access to the space inside larger soil aggregates (Sagee et al., 2012)....

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  • ..., 2003), it is believed to occur at lower ratios also because of the roughness of soil particles (Tufenkji et al., 2004) or because ENM gain access to the space inside larger soil aggregates (Sagee et al....

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Journal ArticleDOI
TL;DR: The results showed that TiO(2) could remain suspended in soil suspensions even after settling for 10 days, and aggregate sizes in the column outflow significantly increased after passing through the soil columns, indicating potential environmental risk of TiO (2) nanoparticles to deep soil layers.

343 citations


Cites background from "Transport of Cryptosporidium Oocyst..."

  • ...Indeed, straining could even be important when the ratio of the particle to median grain diameter was less than 0.002 and if the collector grains were rough and irregular in shape (Tufenkji et al., 2004; Bradford et al., 2002, 2003)....

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  • ...Tufenkji et al. (2004) indicated that a physical removal mechanism, such as straining, which was independent of electrostatic interactions, would play an important role in particle deposition....

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  • ...002 and if the collector grains were rough and irregular in shape (Tufenkji et al., 2004; Bradford et al., 2002, 2003)....

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Journal ArticleDOI
TL;DR: Observations suggest that the extent of colloid removal by straining is strongly coupled to solution chemistry.

342 citations


Cites background from "Transport of Cryptosporidium Oocyst..."

  • ...…that the pore structure can play an important role in colloid deposition under unfavorable attachment conditions (Cushing and Lawler, 1998; Bradford et al., 2002, 2003, 2004, 2005, 2006a–d; Li et al., 2004, 2006a, b; Tufenkji et al., 2004; Bradford and Bettahar, 2005, 2006; Foppen et al., 2005)....

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Journal ArticleDOI
TL;DR: A review of colloid transport and retention at the interface, collector, and pore scales can be found in this article, where the potential for colloid attachment in the presence of hydrodynamic forces and torques is determined from a balance of applied and adhesive torques.
Abstract: Our ability to accurately simulate the transport and retention of colloids in the vadose zone is currently limited by our lack of basic understanding of colloid retention processes that occur at the pore scale. This review discusses our current knowledge of physical and chemical mechanisms, factors, and models of colloid transport and retention at the interface, collector, and pore scales. The interface scale is well suited for studying the interaction energy and hydrodynamic forces and torques that act on colloids near interfaces. Solid surface roughness is reported to have a significant influence on both adhesive and applied hydrodynamic forces and torques, whereas non-Derjaguin–Landau–Verwey–Overbeek (DLVO) forces such as hydrophobic and capillary forces are likely to play a significant role in colloid interactions with the air–water interface. The flow field can be solved and mass transfer processes can be quantified at the collector scale. Here the potential for colloid attachment in the presence of hydrodynamic forces is determined from a balance of applied and adhesive torques. The fraction of the collector surface that contributes to attachment has been demonstrated to depend on both physical and chemical conditions. Processes of colloid mass transfer and retention can also be calculated at the pore scale. Differences in collector- and pore-scale studies occur as a result of the presence of small pore spaces that are associated with multiple interfaces and zones of relative flow stagnation. Here a variety of straining processes may occur in saturated and unsaturated systems, as well as colloid size exclusion. Our current knowledge of straining processes is still incomplete, but recent research indicates a strong coupling of hydrodynamics, solution chemistry, and colloid concentration on these processes, as well as a dependency on the size of the colloid, the solid grain, and the water content.

330 citations

Journal ArticleDOI
TL;DR: Traditional modeling approaches used to predict the migration and removal of microorganisms in saturated porous media are systematically evaluated and recently proposed improvements to the most commonly used filtration model are discussed, with particular consideration of straining and microbe motility.

320 citations


Cites background from "Transport of Cryptosporidium Oocyst..."

  • ...The limited body of literature on this subject is focused on the filtration behavior of Cryptosporidium parvum [1,21,33,54,65,82,133,134] and Giardia lamblia [65]— two waterborne pathogens of considerable concern [81,143]....

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  • ...parvum transport behavior in columns packed with ultrapure quartz sand indicates that both straining and physicochemical filtration (attachment) affect the removal of oocysts from the pore fluid [134]....

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  • ...In most controlled packed-column experiments where the transport of viruses [5,6,28,68,72], bacteria [35,38,40,46,62,63,103,104,119,120,141] or protozoa [54, 134] has been examined, the observed breakthrough has been comparable to that of a tracer....

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  • ...(5)) has been used extensively to evaluate microbial transport and fate in saturated porous media [2,6,19,24,34,37,79,91,93,100,101,103,104,134,141]....

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  • ...Specifically, the role of solution ionic strength and composition [33,65,133,134], grain size and shape [21,54,82,134], fluid velocity [54], and collector surface heterogeneity [1] has been examined....

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References
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Book
01 Jan 1948

5,099 citations

Book
19 Mar 1987
TL;DR: The structure of concentrated dispersions thin films Emulsions Microemulsions Rheology of colloidal dispersions and their properties are described in detail in this paper, with a focus on statistical mechanics of fluids.
Abstract: Introduction to statistical mechanics of fluids Adsorption from Solution The electrokinetic effects The structure of concentrated dispersions Thin films Emulsions Microemulsions Rheology of colloidal dispersions.

3,325 citations

Journal ArticleDOI
TL;DR: In this paper, a quantitative theory is presented which describes the kinetics of coagulation of colloidal systems containing more than one dispersed species, using the linear (Debye-Huckel) approximation for low surface potentials.
Abstract: A quantitative theory is presented which describes the kinetics of coagulation of colloidal systems containing more than one dispersed species. A general expression has been derived to describe the potential energy of interaction between dissimilar spherical colloidal particles, using the linear (Debye-Huckel) approximation for low surface potentials. An overall stability ratio has been defined which takes into account the possibility of interactions between like, as well as unlike, particles in the system. The errors introduced by the use of the linear approximation have been assessed in terms of their effects on the stability ratio, and found to be quite small. The theory has been used to describe the behaviour of a hypothetical system under various conditions.

1,734 citations