A laboratory study was conducted to assess the relationship between degree of volatile organic compound (VOC) mass removal from soil and heating duration, initial dense non-aqueous phase liquid (DNAPL) saturation, and grain size. The relationship between post-remedy sampling temperature and VOC soil concentration was examined. Soil contained in glass jars was spiked with DNAPL phase tetrachloroethylene (PCE), saturated, and placed in an oven for a specified period of time. The soil temperature at the centre of each jar was monitored during heating. Upon removal from the oven, each jar was immediately capped with an air tight seal and placed into an ice bath until the soil temperature had cooled to the desired sampling temperature. The jar caps were subsequently removed and the soil was sampled using a coring tool and immersed into pre-weighed vials containing methanol. PCE in soil samples was quantified using purge-and-trap with gas chromatography/mass spectrometry. Soil temperature increased steadily from ambient until reaching a plateau at 89 ºC ± 4 ºC due to co-boiling of DNAPL phase PCE and water. A linear relationship was found between the length of the co-boiling plateau and the initial PCE saturation. Co-boiling continued until DNAPL phase PCE had been depleted, at which time the soil temperature increased to the boiling point of water and remained constant while remaining pore water was removed. PCE soil concentrations decreased rapidly in the early stages of heating, but leveled off between 9.0 and 19 ppb soon after the soil became dried out. Analysis of the sensitivity to initial PCE saturation data revealed that the concentration of PCE in post-remedy samples increased with increasing initial saturation. Results of the sensitivity to grain size tests showed a decreasing trend between PCE soil concentration and decreasing sand grain size while temperature at sampling was not found to affect the amount of PCE quantified post-thermal remedy. Soil temperature at the centre of each jar during cooling was measured and an analytical solution was fit to the recorded data. From this data, the thermal diffusivity of the soil was approximated and was found to range from 1.4 x 10-7 to 1.8 x 10-7 m2/s. / Thesis (Master, Civil Engineering) -- Queen's University, 2007-12-11 10:12:50.564

The present work is in the area of site and computational investigations dealing with migration of a dense non-aqueous phase liquid (DNAPL) within a discrete fractures network embedded in a porous rock media at field scale using numerical simulation. The migration of DNAPL in the subsurface is dependent upon surface parameters, subsurface aquifer parameters and other subsurface conditions. Generally, these aquifer parameters govern the temporal and spatial variability of a DNAPL. To understand the source zone architecture and dissolved plume movement in the subsurface, characterization of these relevant subsurface parameters is required with respect to space and time. The present study focuses on a systematic investigation and characterization of fluid and transport parameters at highly contaminated fractured-porous media site located at Smithville, Ontario, Canada. Data used to characterize the Smithville site include site geology, ground surface elevation, historical hydraulic head, hydraulic parameters from packer tests such as hydraulic conductivity, porosity, analyses performed on borehole core samples, pumping rates from recovery wells, and contaminants transport parameters such as DNAPL concentration data. Geostatistical and statistical analysis have been used to generate information on groundwater flow direction, vertical hydraulic gradients, contaminant plume migration and source zone architecture. TCE concentrations and pumping rates have been used to estimate TCE mass removal from the site. Important parameters for use in the multiphase model have been developed, including capillary pressure curves and relative permeability curves for rock matrix and fractures, and pore throat radius of the rock matrix. DNAPL behaves differently in fractured-porous media than it does in porous media. To understand DNAPL behaviour in fractured-porous media, site specific conceptual model development to describe geological, hydrogeological, fracture network, and DNAPL occurrence is required. Prediction of the impact of source mass depletion at highly contaminated fractured-porous media site for achieving regulatory goals, as a contaminant concentration at a down gradient compliance boundary was evaluated using multiphase compositional model CompFlow. The results demonstrate that a large amount of non-aqueous phase DNAPL is present in the Vuggy Dolostone and the Tight Dolostone (23-28m, Low Vinemount) and a small amount is present in Permeable Dolostone (Eramosa). The peak concentration at the compliance boundary is much greater than the maximum acceptable concentration (MAC) for TCE of 0.005 mg/L for drinking water.

The present work is in the area of site and computational investigations dealing with migration of a dense non-aqueous phase liquid (DNAPL) within a discrete fractures network embedded in a porous rock media at field scale using numerical simulation. The migration of DNAPL in the subsurface is dependent upon surface parameters, subsurface aquifer parameters and other subsurface conditions. Generally, these aquifer parameters govern the temporal and spatial variability of a DNAPL. To understand the source zone architecture and dissolved plume movement in the subsurface, characterization of these relevant subsurface parameters is required with respect to space and time. The present study focuses on a systematic investigation and characterization of fluid and transport parameters at highly contaminated fractured-porous media site located at Smithville, Ontario, Canada. Data used to characterize the Smithville site include site geology, ground surface elevation, historical hydraulic head, hydraulic parameters from packer tests such as hydraulic conductivity, porosity, analyses performed on borehole core samples, pumping rates from recovery wells, and contaminants transport parameters such as DNAPL concentration data. Geostatistical and statistical analysis have been used to generate information on groundwater flow direction, vertical hydraulic gradients, contaminant plume migration and source zone architecture. TCE concentrations and pumping rates have been used to estimate TCE mass removal from the site. Important parameters for use in the multiphase model have been developed, including capillary pressure curves and relative permeability curves for rock matrix and fractures, and pore throat radius of the rock matrix. DNAPL behaves differently in fractured-porous media than it does in porous media. To understand DNAPL behaviour in fractured-porous media, site specific conceptual model development to describe geological, hydrogeological, fracture network, and DNAPL occurrence is required. Prediction of the impact of source mass depletion at highly contaminated fractured-porous media site for achieving regulatory goals, as a contaminant concentration at a down gradient compliance boundary was evaluated using multiphase compositional model CompFlow. The results demonstrate that a large amount of non-aqueous phase DNAPL is present in the Vuggy Dolostone and the Tight Dolostone (23-28m, Low Vinemount) and a small amount is present in Permeable Dolostone (Eramosa). The peak concentration at the compliance boundary is much greater than the maximum acceptable concentration (MAC) for TCE of 0.005 mg/L for drinking water.

Mathematical modelling was utilized to evaluate trichloroethylene (TCE) and tetrachloroethylene (PCE) dense non-aqueous phase liquid (DNAPL) source zone remediation in the subsurface environment. Semi-analytical solutions were derived, tested, and employed to evaluate the benefits of source zone concentration reduction and solute degradation mechanisms on the evolution of plumes in porous media and fractured rock domains. Simulations of treatment in complex DNAPL source zones using different remedial technologies were completed with a numerical model that was developed, tested, calibrated, and applied to nine idealized heterogeneous porous media sites. Analytical modelling revealed that, in domains dominated by matrix diffusion, aggressive and moderate source zone concentration reduction may have similar effects on the leading edge of the plume. The tailing (near source) edge of the plume may be more responsive to aggressive concentration reduction, particularly when diffusion processes are negligible. Both the near-field (near-source) and far-field plume responses were strongly influenced by the matrix decay half-life for both transient and steady-state conditions. The degradative capacity of the matrix largely dictated plume extent and life-span for the fractured bedrock site considered here. Numerical simulations of in situ source zone treatment with chemical oxidation (ISCO), enhanced bioremediation (ISEB), and surfactants (SEAR) were compared and contrasted. Treatment efficacy was site specific, with benefits observed at some sites, and detrimental impacts observed at others. Each technology demonstrated some degree of performance enhancement relative to dissolution only (no treatment). The maximum DNAPL mass depletion enhancement factors for ISCO, ISEB and SEAR, were 1.44, 2.91, and 2.70 after 10 years, respectively. Similarly, the maximum boundary mass flux enhancement factors for ISCO, ISEB and SEAR were 9.78, 3.32, and 3.97, respectively. While notable enhancements were observed for many sites during active treatment, the long-term performance of pre-maturely terminated ISCO and ISEB, and to a lesser degree SEAR, was similar to dissolution. Overall, the partial depletion of DNAPL mass from source zones produced on-going persistent boundary mass flux signatures. Only the complete removal of DNAPL mass, which was attained for one site with SEAR, successfully eliminated downgradient boundary mass flux. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-05-21 08:55:04.491

A numerical model was utilized to assess the effects of elevated temperature on the application of in situ chemical oxidation (ISCO) and enhanced in situ bioremediation (EISB) for the subsurface remediation of trichloroethene (TCE) and tetrachloroethene (PCE). Temperature adjustment of the contaminant physicochemical properties as well as the chemical/biological reactions associated with ISCO and EISB were accounted for in the model domain. ISCO reaction rates were estimated using Arrhenius principles; microbial growth rates for EISB were estimated using non-linear fits to published literature data. The results from this study showed that temperature did provide remedial benefits to ISCO and EISB treatment during the short-term timeframe of oxidant/substrate injection. During these time periods, heated ISCO and EISB treatment exhibited greater DNAPL mass removal and mass flux reduction compared to heated abiotic dissolution. In the long term, after oxidant/substrate injection was terminated, the treatment enhancements achieved by ISCO and EISB were negated. Permeability (k) reduction due to rind formation (ISCO) and bioclogging (EISB) inhibited DNAPL dissolution and contributed to greater dissolution tailing effects. Tailing effects caused by ISCO were more severe compared to EISB since rind formation contributed to permanent k reduction; partial k recovery was observed in the EISB scenarios due to biomass decay. Even though higher temperatures were beneficial to ISCO and EISB during the short-term oxidant/substrate injection period, treatment efficacy was ultimately controlled by the detrimental by-products (rind from ISCO and biomass from EISB) formed as a result of the associative chemical/biological reactions. / Thesis (Master, Civil Engineering) -- Queen's University, 2014-02-10 18:59:23.177

No description available.

A laboratory scale study was conducted to evaluate the thermal remediation of trichloroethylene (TCE) in a saturated groundwater system using electrical resistance heating (ERH). Two experiments were conducted using a two-dimensional polycarbonate test cell, the first consisting of a single pool of TCE perched above a capillary barrier, the second consisting of two pools of TCE each perched on separate capillary barriers. Temperature data was collected during the heating process from an array of 32 thermocouples located throughout the test cell. Visualization of the vaporization of liquid phase TCE, as well as the upward migration of the produced vapour was recorded using a digital camera. Chemical testing was performed 48 hours after experiment termination to measure post heating soil concentrations. A co-boiling plateau in temperature was found to be a clear and evident earmark of an ongoing phase change in the pooled TCE. Temperature was found to increase more rapidly in the second experiment that included a fully spanning barrier. As temperatures increased above the co-boiling plateau, vapour rise originating from the source zone was observed, and was found to create a high saturation gas zone beneath the upper capillary barrier when no clear pathway was available for it to escape upwards. When the source zones had reached the target temperature of 100°C and the ERH process stopped, this high saturation gas zone condensed, leading to elevated TCE concentrations below as well as within the capillary barrier itself. The water table within the experimental cell was also noted to drop measurably when the gas zone collapsed. Post-testing chemical analysis showed reductions in TCE concentrations of over 99.04% compared to the source zone, although due to condensation of entrapped gas and convective mixing, there was a net redistribution of TCE within the experimental domain, especially within confined areas below the capillary barriers. A secondary set of experiments were conducted using a homogenous silica sand pack with no chemical contaminants to determine the effect, if any, of the wave shape of electrical input on the ERH process. It was found that in early time heating, square wave inputs consistently produced a more localized heating pattern when compared to the standard sine wave electrical input. This effect equalized between the two experiments as the ERH process went on, perhaps due to the increased dominance of conduction and convection as the mode of heat transfer in the test cell at higher temperatures. It is believed that the localization of heating in square wave experiments is due to a consistent power supply due to the lack of a sinusoidal ramping in power delivery. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-03-18 14:40:46.019

Västerås is a city with an industrial heritage. One of the larger companies in Västerås is ABB AB, which has multiply businesses located at the area Finnslätten. High concentrations of trichloroethene (TCE) were found in the soil and groundwater at Finnslätten 1 during a phase II environmental site assessment. Due to the result of the assessment a supplementary investigation and a site specific risk assessment were made of building 358. The source zone and plume of trichloroethene have not been characterized even after several investigations at the site. The aim of this study was to make a risk assessment of three other buildings inside the area were degreasing with TCE have historical taken place. The collected information resulted in a risk class 2 of the three objects and shows that the buildings might be potential pre-emission sources of trichloroethene. The second aim contains a comparison between traditional and alternative approaches to enlighten the importance of effective characterization methods. Two potential characterization strategies were chosen; TRIAD approach and CMF approach. The result showed the importance of systematic project planning, dynamic work planning strategy and the use of multiple techniques to form the best “hybrid” during characterization of DNAPL. In order to bring the investigation to a successful conclusion it is of great importance to consider the uncertainties or diminish the uncertainties by collecting essential information.

An invasion percolation (IP) model was used to illustrate the effects of gravity on DNAPL migration into a horizontal water saturated fracture. While gravity is typically neglected in the conventional approach, this work demonstrated that gravity should often be included when modelling DNAPL invasion in water saturated fractures and provides an equation estimating the difference in invasion pattern between simulations including or neglecting gravity. The IP model was further utilized to examine the invasion of DNAPL saturated fractures by water. These simulated experiments focus on cases where covariance (COV), the ratio of the mean of the aperture field to the standard deviation of the aperture field) as well as when the fracture is inclined or declined from horizontal. Results show that when COV is greater than 0.1, then DNAPL will always remain in the fracture after waterflooding. Furthermore, fracture angles below -15 degrees permit the complete removal of DNAPL, while fractures oriented at higher angles do not. In order to study the transport of particles in water saturated fractures, physical experiments measuring the transport of 0.046 um and 0.55 um microspheres were undertaken on fractures where the geometry could be imported into a computer for comparative simulation analysis. Results demonstrated that during advection, particles generally travel at less than the velocity of the surrounding fluid. As well, hydrodynamic effects such as shear were shown to influence the effluent concentrations by increasing dispersion. Finally, the physical geometry of the fracture was shown to influence the particle pathway during transport and can limit the chances of particles adhering to a fracture wall, thus reducing dispersion and increasing peak concentration. The combined results of these studies show that fracture geometry has a significant effect on the mechanisms of transport in saturated fractures. / Thesis / Doctor of Philosophy (PhD) / This thesis describes the transport of contaminants in rock fractures in the environment. Specifically, the transport of denser than water liquids that are immiscible in water and particles are modelled and analysed. This work used experiments in order to calibrate these models for analysis. It was found that the local geometry of the fracture walls heavily influences the invasion pattern of immiscible dense fluids as well as the retention of the fluids after waterflooding (a first step in remediation). Particle transport was found to be heavily affected by the local geometry in the fracture, specifically lowering the likelihood of attachment to fracture walls limiting the filtration effects, and thus allowing greater contaminants to exit the fracture. Ultimately, these results lead to a greater understanding of the mechanisms of transport in fractured media.

Included in this file is a CD drive titled "Chapter Three: Supporting Information" with a 00:40 second long animation. For best quality, view in VLC, not Quicktime Player. / <p>Groundwater contamination by dense non-aqueous phase liquids (DNAPLs ), such as chlorinated solvents, continues to be a significant environmental problem. When released to the subsurface, either due to improper disposal or accidental release, DNAPLs can form complex source zones whose geometry is largely controlled by the geological heterogeneity of the subsurface. These source zones are composed of disconnected, immobile blobs or ganglia trapped by capillary forces (referred to as DNAPL residual) between high-saturation regions located at permeability interfaces (referred to as DNAPL pools). The slow dissolution of DNAPL pools can result in the contamination of groundwater for time periods on the order of decades to centuries.</p> <p>The common conceptual model used in the investigation of DNAPL-contaminated sites is based primarily on the mass transfer from DNAPL to the surrounding aqueous phase in the saturated zone. However, the presence of a discontinuous gas phase above a DNAPL pool can significantly affect the mass transfer from the pool through repeated, spontaneous expansion and mobilization of the gas phase. This mechanism has not been included in the common conceptual models.</p> <p>The goal of this research was to develop a quantitative understanding of discontinuous gas phase expansion and mobilization above a DNAPL pool. This goal was addressed using a combination of small-scale and intermediate-scale laboratory experiments. Small-scale, no-flow vial experiments were used to measure the expansion of single gas bubbles above DNAPL pools, and provide the basis for the development of an analytical model to assess the effect of expansion by multi-component partitioning on the mass transfer from DNAPL pools. Small-scale flow cell experiments were used to measure spontaneous expansion rates in porous media, and provide visual data concerning the distribution of the gas phase. Small-scale air injection experiments were used to characterize the gas flow. Finally, an intermediate-scale flow cell experiment was used to provide larger-scale data concerning the transient distribution of the gas phase, and measure the effect of spontaneous expansion and mobilization on the aqueous-phase DNAPL constituent concentrations.</p> <p>The combined results of these experiments established a detailed conceptual model for the spontaneous expansion and mobilization of a discontinuous gas phase above a DNAPL pool. In this conceptual model, spontaneous expansion of a discontinuous gas phase above a DNAPL pool occurs due to multi-component partitioning, and depends on the concentrations of both the volatile DNAPL and the other dissolved gases. This expansion is more likely to occur, and will be faster, in shallower systems (i.e. lower hydrostatic pressures) containing coarser media (i.e. lower capillary pressures), more volatile DNAPL, and higher concentrations of other dissolved gases (i.e. higher partial pressures). Mobilization of the expanding gas will occur as discontinuous gas flow in most sands, where the repeated trapping and coalescence of gas clusters can allow rapid, large-scale vertical transport of the gas phase. This discontinuous gas flow can produce macroscopic gas fingers composed of multiple, discrete gas clusters. These macroscopic fingers can reach substantial heights above the pool surface, but the growth occurs predominantly at the pool's leading edge due to the stripping of other dissolved gases. This expansion and mobilization can significantly affect the mass transfer from the DNAPL pool if the gas phase is in direct contact with the pool surface; or if the gas phase is close to the pool surface, covers a large fraction of the pool, and the groundwater flow is sufficiently slow. The partitioning of DNAPL constituent from the mobilized gas phase to the aqueous phase well above the pool surface can also change the spatial distribution of aqueous-phase DNAPL constituent concentrations, increasing them above those that are expected based on theoretical calculations for strictly DNAPL-water systems, even at elevations where the concentrations are expected to be zero. The increased concentrations well above the pool surface can appear as short-duration events in the presence of a sustained gas phase, due to the partitioning of DNAPL constituents from the gas to the aqueous phase during multi-component mass transfer. The results of this research provide the necessary basis to begin incorporating this fundamental mechanism into the conceptual and mathematical models used for DNAPL-related research, the investigation ofDNAPL-contaminated sites, and the design and application of DNAPL remediation technologies.</p> / Thesis / Doctor of Philosophy (PhD)