Influence of organic carbon loading, sediment associated metal oxide content and sediment grain size distributions upon Cryptosporidium parvum removal during riverbank filtration operations, Sonoma County, CA
TL;DR: Although the grain-surface metal oxides were found to have a high colloid-removal capacity, this study suggested that any major changes within the watershed that would result in long-term alterations in either the quantity and (or) the character of the river's DOC could alter the effectiveness of pathogen removal during RBF operations.
About: This article is published in Water Research.The article was published on 2010-02-01. It has received 27 citations till now. The article focuses on the topics: Dissolved organic carbon & Organic matter.
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TL;DR: In this article, a number of transport pathways, processes, factors, and mathematical models often are needed to describe pathogen fate in agricultural settings, and the level of complexity is dramatically enhanced by soil heterogeneity, as well as by temporal variability in temperature, water inputs, and pathogen sources.
Abstract: An understanding of the transport and survival of microbial pathogens (pathogens hereafter) in agricultural settings is needed to assess the risk of pathogen contamination to water and food resources, and to develop control strategies and treatment options. However, many knowledge gaps still remain in predicting the fate and transport of pathogens in runoff water, and then through the shallow vadose zone and groundwater. A number of transport pathways, processes, factors, and mathematical models often are needed to describe pathogen fate in agricultural settings. The level of complexity is dramatically enhanced by soil heterogeneity, as well as by temporal variability in temperature, water inputs, and pathogen sources. There is substantial variability in pathogen migration pathways, leading to changes in the dominant processes that control pathogen transport over different spatial and temporal scales. For example, intense rainfall events can generate runoff and preferential flow that can rapidly transport...
197 citations
Cites background from "Influence of organic carbon loading..."
...Intrinsic surface impurities of the porous medium can generate localized regions where attractive interaction is favorable even when the bulk surface has unfavorable properties (Kim et al., 2008; Metge et al., 2010)....
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...…media (Abudalo et al., 2010; Bradford et al., 2006c; Bradford et al., 2006d; Brown and Jaffé, 2001; Cao et al., 2010; Foppen et al., 2006; Guber et al., 2005a; Guber et al., 2005b; Harvey et al., 2010; Johnson and Logan, 1996; Metge et al., 2010; Pieper et al., 1997; Powelson and Mills, 2001)....
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TL;DR: The model results show that the PDFs of colloid adhesive parameters at the REA scale were sensitive to the size of the colloid and the heterogeneity, the charge and number of grid cells, and the ionic strength.
Abstract: A simple modeling approach was developed to calculate colloid adhesive parameters for chemically heteroge- neous porous media. The area of the zone of electrostatic influence between a colloid and solid−water interface (Az) was discretized into a number of equally sized grid cells to capture chemical heterogeneity within this region. These cells were divided into fractions having specific zeta potentials (e.g., negative or positive values). Mean colloid adhesive parameters such as the zeta potential, the minimum and maximum in the interaction energy, the colloid sticking efficiency (α), and the fraction of the solid surface area that contributes to colloid immobilization (Sf) were calculated for possible charge realizations within Az. The probability of a given charge realization in Az was calculated using a binomial mass distribution. Probability density functions (PDFs) for the colloid adhesive parameters on the heterogeneous surface were subsequently calculated at the representative elementary area (REA) scale for a porous medium. This approach was applied separately to the solid−water interface (SWI) and the colloid, or jointly to both the SWI and colloid. To validate the developed model, the mean and standard deviation of the interaction energy distribution on a chemically heterogeneous SWI were calculated and demonstrated to be consistent with published Monte Carlo simulation output using the computationally intensive grid surface integration technique. Our model results show that the PDFs of colloid adhesive parameters at the REA scale were sensitive to the size of the colloid and the heterogeneity, the charge and number of grid cells, and the ionic strength.
72 citations
TL;DR: A calibrated model provided a satisfactory description of the observed release behavior for a range of colloid types and sizes and a general theoretical foundation to develop predictions for the influence of solution chemistry on the transport, retention, and release of colloids.
Abstract: [1] The transport and fate of colloids, microorganisms, and nanoparticles in subsurface environments is strongly influenced by transients in solution ionic strength (IS). A sophisticated dual-permeability transport model was modified and a theory was developed to mechanistically account for the transport, retention, and release of colloids with transients in IS. In particular, colloid release in the model was directly related to the balance of applied hydrodynamic and resisting adhesive torques that determined the fraction of the solid surface area that contributed to colloid immobilization (Sf). The colloid sticking efficiency (α) and Sf were explicit functions of IS that determined the rates of colloid interaction with the solid, immobilization on the solid, colloid release from the solid and back into the bulk aqueous phase, and the maximum amount of colloid retention. The developed model was used to analyze experimental transport and release data with transients in IS for 1.1 and 0.11 μm latex microspheres, E. coli D21g, and coliphage ϕX174. Comparison of experimental values of Sf(IS) with predictions based on mean interaction energies indicated that predictions needed to account for the influence of physical and/or chemical heterogeneity on colloid immobilization. This was especially true for smaller colloids because they were more sensitive to microscopic heterogeneities that produced mainly irreversible interaction in a primary minimum and greater hysteresis in Sf(IS) with IS. Significant deviations between experimental and predicted values of α(IS) were observed for larger colloids when hydrodynamic forces were not accounted for in the predictions. A sensitivity analysis indicated that colloid release with IS transients was not diffusion controlled, but rather occurred rapidly and with low levels of dispersion. The calibrated model provided a satisfactory description of the observed release behavior for a range of colloid types and sizes and a general theoretical foundation to develop predictions for the influence of solution chemistry on the transport, retention, and release of colloids.
72 citations
Cites background from "Influence of organic carbon loading..."
...It should be mentioned that mean zeta potentials and calculated interaction energies do not account for the influence of microscopic physical and chemical heterogeneity on colloid adhesive parameters [Foppen and Schijven, 2006; Duffadar and Davis, 2007, 2008; Kim et al., 2008; Metge et al., 2010]....
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TL;DR: This review presents the four main geochemical processes relevant for inorganic geochemistry, with a focus on iron (Fe) and manganese (Mn), during bank filtration: reduction near the bank, oxidation near the production well, carbonate dissolution, and sorption to aquifer materials.
Abstract: Bank filtration induces flow of surface water through a hydraulically connected aquifer by excess pumping from a production well in the aquifer. This review presents the four main geochemical processes relevant for inorganic geochemistry, with a focus on iron (Fe) and manganese (Mn), during bank filtration: reduction near the bank, oxidation near the production well, carbonate dissolution, and sorption to aquifer materials. Physical and transport processes affect these geochemical processes and influence the redox state of the infiltrate. The presence of Fe and Mn in bank infiltrate is directly related to its redox status and can necessitate drinking water treatment after extraction. Long-term, in situ sequestration of Fe and Mn requires precipitation of oxide or carbonate solids, since a sorption front can breakthrough at the production well.
70 citations
TL;DR: In this paper, the removal of carboxylated polystyrene (PS) microspheres in a wide size range (3, 6, 25, 45, and 90μm) in two types of real surface waters (Grand River and Lake Erie water) that are sources for full-scale drinking water treatment plants was investigated.
46 citations
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TL;DR: The presenoe of Cl -in concentrations greater than 0.02 M is shown to interfere with the analysis of aqueous DOC concentrations by the wet oxidation method of analysis when a reaction time of 5 min is employed as discussed by the authors.
Abstract: The presenoe of Cl - in concentrations greater than 0.02 M is shown to interfere with the analysis of aqueous DOC concentrations by the wet oxidation method of analysis when a reaction time of 5 min is employed. Chloride competes with DOC for S 2 O 8 2- lowering the overall oxidation efficiency. The resulting HOCl from the oxidation of Cl - reacts with DOC, producing significant amounts of chlorinated intermediate compounds in addition to CO 2 .
160 citations
"Influence of organic carbon loading..." refers methods in this paper
...Concentrations of aquatic humic substances were measured chromatographically by following the procedures described by Aiken (1992)....
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...Dissolved organic carbon (DOC) concentration was determined using an OI Analytical 700 TOC analyzer (Aiken, 1992)....
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TL;DR: In this article, Saturated column studies were undertaken to characterize the straining behavior of negatively charged latex colloids (1.1 and 3.0 μm) at textural interfaces.
Abstract: [1] Although natural soil and aquifer systems often contain layers and lenses of contrasting soil texture, relatively little research has focused on the mechanisms of colloid deposition at textural interfaces. Saturated column studies were undertaken to characterize the straining behavior of negatively charged latex colloids (1.1 and 3.0 μm) at textural interfaces. Mechanisms of colloid transport and retention were deduced from measured effluent concentration curves, final spatial distributions in the columns, mass balance information, microscopic examination of deposition behavior in micromodel experiments, and numerical modeling. Transport and deposition of colloids were found to be highly dependent upon the textural interface. Deposition of colloids in a given sand was always most pronounced at the sand (inlet) surface. Here colloids enter a new pore network and are more likely to encounter smaller pores or dead-end regions of the pore space that contribute to straining. Less deposition occurred at textural interfaces within the column than at the sand surface. We believe that this is due to the fact that advection, dispersion, and size exclusion tend to confine colloid transport to the larger pore networks, thus limiting accessibility to straining sites. Increasing the textural contrast at an interface produced greater colloid deposition when water flowed from coarser- to finer-textured sands. Conversely, when water flowed from finer- to coarser-textured sands, little deposition occurred. Numerical modeling indicates the need to account for blocking (filling) and accessibility of straining sites in layered systems. A previously developed straining model was modified to account for this behavior.
155 citations
TL;DR: Oocyst deposition behavior is shown to deviate from predictions based on classical colloid filtration theory in the presence of repulsive (unfavorable) colloidal interactions, having important implications for predictions of oocyst transport in subsurface environments, where repulsive electrostatic interactions predominate.
Abstract: Spatial distributions of Cryptosporidium parvum oocysts in columns packed with uniform glass-bead collectors were measured over a broad range of physicochemical conditions Oocyst deposition behavior is shown to deviate from predictions based on classical colloid filtration theory (CFT) in the presence of repulsive (unfavorable) colloidal interactions Specifically, CFT tends to predict greater removal of oocysts (less transport) than that observed in controlled laboratory experiments Comparison of oocyst retention with results obtained using polystyrene latex particles of similar size suggests that mechanisms controlling particle deposition are the same in both systems At a given ionic strength, the deposition of Cryptosporidium oocysts is generally greater than that of the microspheres; however, this discrepancy is partly attributable to large differences in oocyst and microsphere zeta potentials A dual deposition mode (DDM) model is applied which considers the combined influence of “fast” and “slow”
129 citations
"Influence of organic carbon loading..." refers background in this paper
...Additionally, Tufenkji and Elimelech (2005) point out that laboratory experiments with model sediments cannot account for the various factors, namely metal oxide coatings and organic matter that impact the degree of oocyst removal....
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TL;DR: Results of this study demonstrated the potential for RBF to provide substantial reductions in microorganism concentrations relative to the raw water sources and further research is needed to better understand the relationships among transport of pathogens and potential surrogate parameters during RBF.
123 citations
"Influence of organic carbon loading..." refers background in this paper
...A recent study by Weiss et al. (2005) concluded that simple monitoring for pathogens – which can occur episodically at RBF sites, may be inadequate for assessing log removal rates (and therefore treatment credits)....
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TL;DR: Field and laboratory results suggest that 2-(mu)m carboxylated microspheres may be useful as analogs in investigating several abiotic aspects of flagellate transport behavior in groundwater.
Abstract: Transport behaviors of unidentified flagellated protozoa (flagellates) and flagellate-sized carboxylated microspheres in sandy, organically contaminated aquifer sediments were investigated in a small-scale (1 to 4-m travel distance) natural-gradient tracer test on Cape Cod and in flow-through columns packed with sieved (0.5-to 1.0-mm grain size) aquifer sediments. The minute (average in situ cell size, 2 to 3 (mu)m) flagellates, which are relatively abundant in the Cape Cod aquifer, were isolated from core samples, grown in a grass extract medium, labeled with hydroethidine (a vital eukaryotic stain), and coinjected into aquifer sediments along with bromide, a conservative tracer. The 2-(mu)m flagellates appeared to be near the optimal size for transport, judging from flowthrough column experiments involving a polydispersed (0.7 to 6.2 (mu)m in diameter) suspension of carboxylated microspheres. However, immobilization within the aquifer sediments accounted for a log unit reduction over the first meter of travel compared with a log unit reduction over the first 10 m of travel for indigenous, free-living groundwater bacteria in earlier tests. High rates of flagellate immobilization in the presence of aquifer sediments also was observed in the laboratory. However, immobilization rates for the laboratory-grown flagellates (initially 4 to 5 (mu)m) injected into the aquifer were not constant and decreased noticeably with increasing time and distance of travel. The decrease in propensity for grain surfaces was accompanied by a decrease in cell size, as the flagellates presumably readapted to aquifer conditions. Retardation and apparent dispersion were generally at least twofold greater than those observed earlier for indigenous groundwater bacteria but were much closer to those observed for highly surface active carboxylated latex microspheres. Field and laboratory results suggest that 2-(mu)m carboxylated microspheres may be useful as analogs in investigating several abiotic aspects of flagellate transport behavior in groundwater.
120 citations
"Influence of organic carbon loading..." refers background in this paper
...However, it has been reported that microspheres within size classes bracketing groundwater protists and oocysts (2–5-mmdiameter) display transport behaviors similar to those of groundwater nanoflagellates (protozoa) (Harvey et al., 1995)....
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