2004 Progress Report: In-Situ Containment and Treatment of Contaminated Sediments: Engineering Cap Integrity and Reactivity

EPA Grant Number: R828773C002
Subproject: this is subproject number 002 , established and managed by the Center Director under grant R828773
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (2001) - South and Southwest HSRC
Center Director: Reible, Danny D.
Title: In-Situ Containment and Treatment of Contaminated Sediments: Engineering Cap Integrity and Reactivity
Investigators: Wiesner, Mark R. , Hughes, Joseph B , Willson, Clinton S. , Valsaraj, Kalliat T. , Edge, Billy
Institution: Rice University , Texas A & M University , Louisiana State University - Baton Rouge , Georgia Institute of Technology
Current Institution: Rice University , Georgia Institute of Technology , Louisiana State University - Baton Rouge , Texas A & M University
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 2001 through September 30, 2006 (Extended to September 30, 2007)
Project Period Covered by this Report: October 1, 2003 through September 30, 2004
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management

Objective:

Georgia Institute of Technology and Louisiana State University Portion
Principal Investigators: J.B. Hughes, K.T. Valsaraj

The primary objective of this collaborative project is to understand the fundamental processes controlling the stability and effectiveness of ‘reactive’ remedial sediment caps. Capping has proven to be an effective approach for isolating contaminated sediments from the aquatic environment. However, gas generated during the degradation of sedimentary organic matter may destabilize contaminants present in the sediment as well as provide a separate phase for partitioning and transport. The rate of gas generation in sediments is key for determining the effect gas ebullition has on cap integrity and understanding the fundamentals of contaminant transport in the presence of gas phase advective movement in the sediment/cap layers. Locations with active groundwater seeps are currently a deterrent for capping as a remedial option. Research is needed to learn how caps, specifically bioactive caps, could be used to transform common groundwater contaminants to nontoxic products during transport through sediment.

Texas A&M University Portion
Principal Investigator: B.L. Edge

The objectives of this component are simply stated as:

  1. Provide a complete and operational extended two-dimensional hydrodynamic and transport model, with serial and parallel computational versions, that can determine risk of sediment caps being scoured, suspended, and deposited in a hurricane or other rare event.
  2. Establish a basis for directly estimating the effects of major, episodic dynamic events that will affect the net circulation of the water and sediment fluxes and suspension in coastal waters. This would be in combination with an extreme event that would resuspend contaminated sediments that contain contaminants that exhibit a “hockey stick” type of desorption.
  3. Implement the coupled hydrodynamic-transport and wave numerical model system as a step toward a natural estuary configuration.

Rice University Portion
Principal Investigator: M.R. Wiesner

The objective of this work was to create sediment caps, tailored for strength and semi-permeable properties, from bentonite/cement composites. We have created various cap microstructures by controlling post-depositional chemical processes in a cap. The technological appeal of this choice is due to the richness of design choices stemming from the complexity of the microstructure and strength development in cementitious materials. By judiciously choosing cement/bentonite and liquid/solid ratios of the composite, desired transport and mechanical properties of the reactive barrier may be attained. Controllable permeability and the capacity of cementitious materials to bind heavy metals make such barriers especially attractive.

Progress Summary:

Georgia Institute of Technology and Louisiana State University Portion
Principal Investigators: J.B. Hughes, K.T. Valsaraj

A digital camera (Photron Motion Tools) was used to take pictures of methane gas bubbles in the column at five different flow rates (3 mL/min to 12 mL/min). The bubble size distributions were obtained using image processing software (J-image). The mean and the mode of the distribution were 0.217 mm and 0.09 mm respectively, with a minimum of 0.019 mm and a maximum of 2.864 mm. Kgw values for phenanthrene were obtained from water sand experimental data for different flowrates.

Parameters kg of phenanthrene between aqueous phase and methane gas bubble in water solution and sediment slurry with different ratios of water to sediment were measured. Figure 1 shows a plot of Kgw for the different solutions as a function of gas flowrate through the column. As the flowrate, Q, increases, a decrease in the value of Kgw Kgw is observed. The value of kwb, the water-bubble phenanthrene mass transfer coefficient, is expected to increase with the higher bubble velocities in the system through increased turbulence. The observation suggests that an increase in Q and the resultant decrease in residence time have a greater influence on the equilibrium partitioning than the relative increase in kwb. The value of Kgw increases slightly with an increase in solids concentration. This suggests that, at higher solids concentration, the presence of slurry solids might be increasing the kwb. This aspect will be investigated further in future experiments.

Figure 1.
Figure 1. Effect of Methane Gas Flow Rate on Phenanthrene Partition Constant, Kgw

Figure 2 shows the effect of phenanthrene removed from the water column using methane bubbles as a function of time for different sediment solids content. The rate of phenanthrene loss from water or slurry solutions to methane gas bubbles is almost constant for the duration of the experiments for all the cases as indicated by the constant slope of the plots in Figure 2. As the solids content in the solution was increased, a decrease in loss to methane bubbles was observed, indicating lesser availability of chemical in the water due to higher retardation from the solids.

Figure 2.
Figure 2. Effect of Solids Content on Phenanthrene Removal From Water

Tetrachloroethene Dechlorination in River Sediment (Hughes). The ability of Anacostia River sediment to transform typical groundwater contaminants was investigated using tetrachloroethene (PCE) as a representative contaminant. PCE is a contaminant found at numerous Superfund sites as a dense nonaqueous phase liquid (DNAPL) with plumes extending downgradient. PCE can be reduced under anaerobic conditions to daughter products—trichloroethene (TCE), cis-dichloroethene (cis-DCE), vinyl chloride (VC), ethene, and finally ethane through a microbial process of reductive dechlorination. Batch reactors were constructed to investigate if Anacostia River sediment could support the reductive dechlorination of PCE. Two separate studies were performed: (1) sediment that was bioaugmented with a mixed culture; and (2) sediment that had not been bioaugmented. Both studies were conducted in microcosms loaded with Anacostia River sediment, simulated groundwater, and PCE. The bioaugmented microcosms were amended with 0.5 mL (< 2% total liquid volume) biomass from an anaerobic mixed culture capable of degrading PCE to ethene in aqueous media. It should be noted that no electron donor or mineral media were added to the batch systems in an attempt to accurately replicate natural environmental conditions in the sediment. Both the bioaugmented and natural sediment were rotated in the dark at 150 rpm at 22°C. An abiotic control was prepared in the same manner, but autoclaved for 1 hour on 2 consecutive days prior to PCE addition. A second control was prepared with sand as the solid phase instead of river sediment. A third control was established that was loaded with river sediment, but not with PCE to ensure that no chlorinated ethenes were present on the sediment. Headspace samples from the microcosms were obtained and analyzed for chlorinated ethenes, ethene, ethane, and methane with gas chromatography/flame ionization detector (GC/FID). Total contaminant mass (gas phase, liquid phase, and solid phase) in the system was calculated based on published Henry’s Law and organic carbon partitioning coefficients for each chemical, with a nonequilibrium sorption rate used for PCE at short times (under 5 days). The nonequilibrium sorption rate was derived from the results of the abiotic sediment control and discussed below.

The bioaugmented sediment was able to dechlorinate PCE to ethene in approximately 25 days following the initial injection of PCE. About 60 percent of the total contaminant mass in the system was sorbed to the sediment and not converted to ethene. Following the second PCE injection, a 120 percent conversion of PCE to ethene occurred in roughly 16 days. The extra 20 percent is due to desorption of contaminants off the sediment. The decreased time required for complete dechlorination is attributed to growth of the dechlorinating microbial population following the first injection of PCE. In the third PCE injection, 100 percent conversion of PCE to ethene occurred, followed by a full conversion to ethane. The conversion to ethane was unexpected since, in aqueous media, the mixed culture’s dechlorination end product was ethene. This suggests that the ethene to ethane converting bacteria are native to the Anacostia River sediment. Also, these results demonstrate the ability of the Anacostia River sediment to support reductive dechlorination, without the need for external electron donor and mineral media.

The natural, unbioaugmented Anacostia River sediment was also able to successfully convert PCE to ethene without additional electron donor or mineral media. The dechlorination of PCE to ethene for the initial PCE injection required 85 days. Roughly 46 percent of the total contaminant mass was sorbed to the sediment, and not converted to ethene. A second injection of PCE into the system yielded ethene in 20 days, again with less time required for complete dechlorination due to a buildup of the microbial dechlorinating population. Transformation of ethene to ethane began 34 days after the second PCE injection. This confirms that the ethene to ethane converting bacteria are native to the Anacostia River sediment. Microbial analysis of the unbioaugmented sediment was performed in order to determine what bacteria were responsible for the dechlorination. DNA was extracted from the unbioaugmented sediment, with target genes and enzymes amplified by PCR. The results show a number of microorganisms present that are capable of reductive dechlorination, suggesting that this is not a cometabolic process. So far, however, there has been no identification of the bacteria responsible for the crucial VC to ethene transformation and the ethene to ethane transformation. It is anticipated that identification of these bacteria will be possible after further enrichment of the sediment.

The experimental controls confirmed that the dechlorination was indeed a microbial process, and that the electron donor and minerals were derived from the sediment. The abiotic control resulted in no dechlorination of PCE and no methanogenic activity. Nonequilibrium sorption of PCE to the abiotic sediment was observed and modeled using a rate-limited sorption model in order to ascertain the rate of sorption. This rate was then used to estimate the amount of PCE mass on the solid phase during mass balance calculations. The organic-carbon partitioning coefficient (Koc) for PCE was measured at equilibrium to be 312 mL PCE/g organic carbon, which is in good agreement with literature values (average value of 272 mL PCE/g OC). The sand control also resulted in no dechlorination and no methanogenic activity, confirming that the sediment must provide the carbon source, electron donor, and mineral requirements of the microorganisms. The PCE-free control demonstrated no desorption of field-contaminated chlorinated ethenes.

These outcomes suggest that in natural systems, it is feasible that PCE-contaminated groundwater can be converted to nontoxic end products through microbial dechlorination in the sediment. In this case, river sediment is acting as a permeable reactive barrier, transforming toxic contaminants before entering the overlying water body. This suggests that bioaugmentation, and even natural attenuation, may be suitable remedial options for groundwater seeps. This is underscored by the apparent ubiquity of dechlorinating microorganisms in the Anacostia River and in groundwater aquifers, as discussed in numerous published articles. Moreover, no previous documented chlorinated solvent contamination exists for the Anacostia River, making these experiments an effective “worst-case” scenario. Sediments that have previously been exposed to chlorinated solvents may dechlorinate PCE faster, since the microbial populations would be larger. It is recommended that more sediments be analyzed for their dechlorinating ability and that column studies be performed in order to more fully address the feasibility of bioaugmentation and natural attenuation as remedial options. Also, the enrichment of the dechlorinating sediment will continue in an attempt to obtain a mixed culture able to dechlorinate PCE to ethane. This culture can then be used for bioaugmentation in the future. During this enrichment process, an emphasis will be placed on understanding the ethene to ethane conversion more fully. This is an uncommon end product of reductive dechlorination, and deserves attention. More research is needed to better understand dechlorination in sand (i.e., iron reducing) systems. The results will be important for designing sand-based bioactive caps.

Students Supported.

David Himmelheber, Ph.D. candidate (Hughes)
Qingzhong Yuan, Ph.D. candidate (Valsaraj)

Texas A&M University Portion
Principal Investigator: B.L. Edge

This research will lead to a better understanding of the characteristics of spatial and temporal variation of contaminated sediment transport in a particular bay, estuaries, or coastal areas during a natural condition or a specific storm event. Thus, the pattern of sediment transport and deposition is associated with the prevailing tidal currents, wind, and waves. The understanding of this process provides a basis for determining how the water circulation and combined wave–current interaction controls the hydrodynamics of the system and ultimately the bed-load and suspended-load transport of sediments.

Up to this stage, we have successfully developed the parallel and serial versions of the model of two-dimensional transport of sediments and have coupled this with the wave model. The inclusion of current and wave factors to estimate erosion and deposition for sediment transport are the most advanced results. The conservation of mass among eroded, suspended, and deposited sediments has been carefully investigated with positive results. Implementation of the model to the Matagorda Bay for the Hurricane Carla event demonstrates the ability to predict the movement of uncapped contaminated sediments or the movement of capping material.

Students Supported

Wahyu W. Pandoe, graduate student, Texas A&M University

Rice University Portion
Principal Investigator: M.R. Wiesner

From a diffusion test with 1 mm glass bead, molecular diffusivity of chlorine was determined to be 1.43·10-5 cm2/s, which compares well with values computed from empirical correlations. This value was used in the model to compute apparent diffusion coefficients for all other cap materials studied in this work. For the sand cap, for example, this value resulted in the remarkable match between porosity measured experimentally and porosity computed as a result of the least square fit of model concentration profile to the measured one.

Figure 3 represents experimentally determined and modeled chlorine concentration profiles in the model sediment after 840 hours of diffusion through the CEM50H cap.

Figure 3.
Figure 3. Chlorine Concentration as a Function of Depth of the Model Sediment Capped With CEM50H Composite

Testing of Mechanical Properties of Bentonite-Cement Composites

Setting Tests. Mechanical stability is an important characteristic of the sediment cap. To evaluate the dynamics of strength development in composite caps, setting times were determined using a standard method that involves a Vicat apparatus. Initial setting time and final (when applicable) setting time were determined (Figure 4). Setting time may be used as a characteristic time in the expression for the time-dependent porosity of such composites.

Figure 4.

Figure 4.

Figure 4. Illustration of Vicat Apparatus (Top) and Dependence of CEM20 Composite Strength on Time

Setting time depended both on the cement fraction and liquid/solid ratio. As anticipated, strength developed faster in caps with higher cement content and lower liquid/solid ratio. It was observed that for the final setting to occur, cement fractions higher than 33 percent were necessary.

Flowability. Various techniques have been used to place the cap on top of the contaminated sediment. All of them, however, involve settling of the concentrated slurry of capping materials through the water column. To measure flowability of cement-bentonite composites, the standard test (ASTM C 230–90) was performed for various liquid/solid ratios and cement contents. Flowability increased with an increase in liquid/solid ratio, as expected (see Figure 5). The dependence of flowability on the cement fraction, however, was not linear, which is attributable to concentration-dependent interactions between clay and cement particles.

Figure 5.
Figure 5. Chlorine Concentration as a Function of Depth of the Model Sediment Capped With CEM50H Composite

Microstructural Studies

To correlate observed macroscopic transport characteristics to the cap microstructure, information on cap porosity has to be obtained. In this section, we describe several approaches we are taking to better understand how the microstructure develops in cement/bentonite composites.

Characterization of Cap Constituents. First, morphology and elemental content of cap components were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and particle sizing. Bentonite particle and particle aggregates were found to be smaller than 10 microns with the following elemental composition: Na2O 2.75 percent, MgO 3.48 percent, Al2O3 23.82 percent, SiO2 68.81 percent, CaO 0.2 percent, and Fe2O3 0.94 percent. Cement particles were smaller than ca. 60 microns and, in terms of elemental composition, were of two types. Type I contained Al2O3 5.61 percent, SiO2 46.63 percent, CaO 43.49 percent, Fe2O3 0.72 percent, and SO3 3.76 percent. Type II (sulfur rich) contained Al2O3 3.71 percent, SiO2 6.78 percent, CaO 34.79 percent, Fe2O3 0.31 percent, and SO3 54.41 percent.

Thus, based on the EDX spectra of individual grains, it is possible to discriminate different cap components. In addition, there was a morphological difference between bentonite and cement particles, the former having a more flaky appearance.

To investigate the effects of hydration on the morphology of cement grains, SEM images of cement samples hydrated at three different water/cement ratios (L/S = 0.3, 0.4, 0.5) were recorded for different stages of hydration. A significant decrease in porosity was observed after 14 days of hydration, more so in samples with lower L/S ratio. Both type and amount of various hydration products, such as ettringite and syngenite varied as functions of time and L/S fraction.

SEM Morphological Characterization of Bentonite-Cement Composites. Effects of cement/bentonite ratio on the morphology of pore space in composite caps were studied using SEM and IDX elemental mapping.

Back-Scattered SEM Imaging. Back-scattered SEM imaging is a convenient method of identifying distinct cement phases and bentonite platelets in composites.

Recommendations. We propose bentonite/cement composite as a new capping material for the isolation of contaminated sediments. By controlling post-depositional chemical processes in a forming composite, it is possible to arrive at different cap microstructures leading to different mechanical and transport characteristics of the capping layer. Cement fraction and the extent of hydration of the composite appear to be the most important factors determining the overall performance of the cap.

Students Supported

Volodymyr Tarabara (graduated, currently assistant professor, Michigan State University).

Future Activities:

Georgia Institute of Technology and Louisiana State University Portion
Principal Investigators: J.B. Hughes, K.T. Valsaraj

Proposed Efforts Over the Next Year. In the next year, the following tasks will be addressed:

  1. Determine the rates of gas migration in typical capped sediments (Valsaraj and Willson).
  2. Assess the contaminant transport within gas bubbles from a contaminated sediment column at typical gas flow rates observed in the field (Valsaraj and Willson).
  3. Investigate the structural changes and secondary porosity formed during gas bubble transport through sediments (Valsaraj and Willson).
  4. Perform column studies with sediment and contaminated groundwater to examine the effectiveness of sediment as a biobarrier (Hughes).
  5. Enrich the PCE to ethane microbial community found in the Anacostia River sediment (Hughes).
  6. Investigate the ethene to ethane conversion observed in the Anacostia River sediment (Hughes).

Task (a) will again be evaluated by measurement of gas ebullition rates in undisturbed cores collected from sediments. Gas generation rates will be compared to the amount and type of organic matter found in the sediments. In Tasks (b) and (c), column experiments similar to those described in this report will be used to evaluate contaminant transport as a result of gas movement and the effect of the gas growth and movement on the structural integrity of the sediment and/or cap. The goal of the task is to ascertain the structural (physical) changes and secondary porosity that would be observed within a sediment column as a result of bubble growth and migration.

The column studies mentioned in Task (d) stem from the promising results of the dechlorination batch studies discussed above. The batch studies with the Anacostia sediment demonstrated that PCE could be converted via microbial reductive dechlorination to nontoxic end products in well mixed, closed systems. Column studies will investigate the ability of Anacostia sediment to dechlorinate PCE under various flow and capping conditions. Also, phenanthrene will be spiked into the sediment to be used as a representative polycyclic aromatic hydrocarbon (PAH) to examine the effect of capping on the biodegradation of PAHs in aerobic environments. Experiments will be performed to address if and how various submarine groundwater discharge rates affect the dechlorination of PCE. The batch studies showed that the sediment is able to provide the energy and mineral needs required by microorganisms for dechlorination under static conditions. It is hypothesized, however, that advective flow will limit the extent of dechlorination due to decreased contaminant residence times in the sediment and washout of electron donors and nutrients. As discussed above, roughly 15 days were required for complete dechlorination in the batch studies. Under the advective conditions of a groundwater seep, the residence time of contaminants in the sediment will be decreased. Thus, the rate of dechlorination may not be able to keep up with the rate of PCE transport through the sediment. In addition, the introduction of advective flow to the sediment may carry electron donors and nutrients from the sediment into the overlying water. Key microbial requirements would therefore not be available for the dechlorinating population, effectively increasing the time required for complete dechlorination. Various flow rates will be examined in order to determine the most favorable seepage velocity for dechlorination.

Various capping scenarios, and their effect on microbial processes, will also be investigated using column experiments. Clean sand will be added to the top of the sediment to mimic in situ caps utilized in the field. The effect of capping on the dechlorination of PCE is uncertain. On one hand, no dechlorination is expected in sand without the addition of electron donor and mineral media, as demonstrated by the second control in the dechlorination batch studies. During advective flows, however, any washout of electron donor and minerals from the sediment will pass through the sand cap, possibly supporting further dechlorination. Migration of microorganisms from the sediment into the sand cap will be monitored, through porewater sampling and microbial analysis, to assess whether dechlorination is occurring in the cap. It is also possible that a sand cap would not provide any advantage for transforming contaminants. This is due to the lack of organic matter and the consequential change in redox conditions in the sediment. After emplacement of the sand cap, the original sediment–water interface shifts from an oxic to anoxic region. Hydrophobic organic contaminants that are biodegraded in oxic environments, such as PAHs, may not be transformed in the new oxic layer of the sand caps due to shorter residence time in the sand (less retardation) and the potential lack of microorganisms present. As discussed earlier, the lack of microorganisms in the sand may prevent dechlorination as well.

An alternative remedial option to sand caps is to emplace a bioactive cap, capable of destroying the contaminants as they are transported through it and into the overlying water. Bioaugmentation of the sediment and cap with a microbial population capable of transforming the contaminants is one possibility. It has been demonstrated that the sediment from the Anacostia River contains such a population. Task (e) centers on enriching this population for potential use in future bioaugmentation practices. The population has demonstrated its ability to convert PCE to ethane with the energy and nutrients provided by the sediment. Enriching the dechlorinating population in the sediment would most likely decrease the time required for ethane production from PCE. These bacteria could be used in the column studies to examine the effect of bioaugmentation on PCE dechlorination in sediment and caps. Also, it is anticipated that enrichment would allow for identification of the bacterium responsible for the vinyl chloride to ethene conversion. This is the key step in the dechlorination process, since PCE is a potential carcinogen and vinyl chloride is a known carcinogen. Only a couple of bacteria have been isolated that can metabolically dechlorinate vinyl chloride to ethene. Identification of the bacteria present in the Anacostia River will allow for optimization of the conditions necessary for the vinyl chloride to ethene conversion.

Task (f) involves a more detailed investigation of the ethene to ethane reaction observed in the unbioaugmented Anacostia River sediment. Ethane as an end product of microbial dechlorination has been reported previously, but is relatively uncommon. More research is needed to understand the processes and microbes responsible. The presence of dechlorinating bacteria, including those responsible for the ethene to ethane conversion, in the Anacostia River is interesting, since no previous documented chlorinated solvent contamination exists for the river. The bacteria may be present because they are capable of using substrates and electron acceptors other than chlorinated solvents, such as PCBs or chlorinated benzenes. If this is the case, then the bioaugmentation discussed in proposed Task (b) would not only be applicable to chlorinated solvent sites, but to sites with other contamination as well. The eventual outcome of each of these final three tasks is to aid in the design of a bioactive cap that is capable of transforming contaminants in situ.


Journal Articles on this Report : 7 Displayed | Download in RIS Format

Other subproject views: All 20 publications 8 publications in selected types All 8 journal articles
Other center views: All 279 publications 92 publications in selected types All 63 journal articles
Type Citation Sub Project Document Sources
Journal Article Pandoe WW, Edge BL. Three-dimensional hydrodynamic model, study cases for quarter annular and idealized ship channel problems. Ocean Engineering 2003;30(9):1117-1135. R828773 (2004)
R828773 (Final)
R828773C002 (2002)
R828773C002 (2003)
R828773C002 (2004)
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  • Journal Article Pandoe WW, Edge BL. Cohesive sediment transport in the 3D-hydrodynamic-baroclinic circulation model: study case for idealized tidal inlet. Ocean Engineering 2004;31(17-18):2227-2252. R828773 (2004)
    R828773 (Final)
    R828773C002 (2004)
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  • Journal Article Tarabara VV, Pierrisnard F, Parron C, Bottero J-Y, Wiesner MR. Morphology of deposits formed from chemically heterogeneous suspensions: application to membrane filtration. Journal of Colloid and Interface Science 2002;256(2):367-377. R828773 (2004)
    R828773 (Final)
    R828773C002 (2002)
    R828773C002 (2003)
    R828773C002 (2004)
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  • Journal Article Tarabara VV, Hovinga RM, Wiesner MR. Constant transmembrane pressure vs. constant permeate flux: effect of particle size on crossflow membrane filtration. Environmental Engineering Science 2002;19(6):343-355. R828773 (2004)
    R828773 (Final)
    R828773C002 (2004)
  • Abstract: Liebert-Abstract
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  • Journal Article Tarabara VV, Wiesner MR. Computational fluid dynamics modeling of the flow in a laboratory membrane filtration cell operated at low recoveries. Chemical Engineering Science 2003;58(1):239-246. R828773 (2004)
    R828773 (Final)
    R828773C002 (2004)
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  • Journal Article Tarabara VV, Koyuncu I, Wiesner MR. Effect of hydrodynamics and solution ionic strength on permeate flux in cross-flow filtration: direct experimental observation of filter cake cross-sections. Journal of Membrane Science 2004;241(1):65-78. R828773 (2004)
    R828773 (Final)
    R828773C002 (2004)
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  • Journal Article Tarabara VV, Wiesner MR. Physical and transport properties of bentonite-cement composites: a new material for in situ capping of contaminated underwater sediments. Environmental Engineering Science 2005;22(5):578-590. R828773C002 (2004)
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  • Supplemental Keywords:

    gas phase contaminant transport, gas bubble, cap structure, cap stability, bioremediation, microbial processes, two-dimensional hydrodynamic, parallel computation, sediment transport, finite element method, cohesive and noncohesive sediments, Matagorda Bay,, RFA, Scientific Discipline, Waste, Water, Contaminated Sediments, Remediation, Environmental Chemistry, Analytical Chemistry, Hazardous Waste, Ecology and Ecosystems, Engineering, Hazardous, Environmental Engineering, contaminant transport, fate and transport , in situ remediation, contaminant dynamics, sediment caps, computer models, contaminated sediment, kinetic studies, contaminated soil, computer modeling, contaminant transport model, treatment, kinetic models, contaminant management

    Relevant Websites:

    http://www.hsrc-ssw.org Exit

    Progress and Final Reports:

    Original Abstract
  • 2002 Progress Report
  • 2003 Progress Report
  • 2005
  • 2006
  • Final

  • Main Center Abstract and Reports:

    R828773    HSRC (2001) - South and Southwest HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R828773C001 Bioturbation and Bioavailability of Residual, Desorption-Resistant Contaminants
    R828773C002 In-Situ Containment and Treatment of Contaminated Sediments: Engineering Cap Integrity and Reactivity
    R828773C003 Phytoremediation in Wetlands and CDFs
    R828773C004 Contaminant Release During Removal and Resuspension
    R828773C005 HSRC Technology Transfer, Training, and Outreach