Little is known about the enzyme-substrate interactions occurring during the dechlorination of chloroform (CF) and 1,1,1-trichloroethane (1,1,1-TCA) by the enrichment culture containing Dehalobacters, hereafter called DHB-CF/MEL. Compound specific isotope analysis (CSIA) is used to investigate the factors which may affect the isotope fractionation observed for CF and 1,1,1-TCA dechlorination. This thesis reports the first isotope enrichment factors observed for CF biodegradation at -27.5‰ ± 0.9‰, thus providing fundamental information for comparing isotope enrichment factors observed during trichlorinated alkane degradation by DHB-CF/MEL. The thesis also reports how the presence of CF and 1,1,1-TCA influences isotope fractionation and explores the possible influence of substrate inhibition on isotope fractionation during 1,1,1-TCA dechlorination. The data suggests that substrate inhibition during 1,1,1-TCA dechlorination by DHB-CF/MEL may not affect carbon isotope fractionation. The results suggest that CSIA is a promising monitoring tool even for the simultaneous biodegradation of CF and 1,1,1-TCA at different 1,1,1-TCA starting concentration.

In situ chemical oxidation (ISCO) is a leading-edge technology for soil and groundwater remediation, and involves injecting a chemical oxidant (e. g. , permanganate, hydrogen peroxide, or persulfate) into the subsurface to deplete contaminant mass through oxidation. Since the delivery of the chosen oxidant to the target treatment zone must occur in situ, the interaction between the injected oxidant and the aquifer material is a key controlling factor for a successful ISCO application. While many published ISCO studies have focused on the interaction between an oxidant and target contaminants, many questions still remain on the interaction between a potential oxidant and the aquifer material. Through a series of bench-scale experiments with aquifer materials collected from 10 sites throughout North America, the research presented in this thesis provides insight into the interaction between these aquifer materials and two widely used ISCO oxidants; permanganate and hydrogen peroxide. <br /><br /> The investigation into the interaction between aquifer materials and permanganate consisted of three series of bench-scale experiments: (1) long-term batch experiments which were used to investigate permanganate consumption in response to fundamental geochemical properties of the aquifer materials, (2) short-term batch experiments which were designed to yield kinetic data that describe the behavior of permanganate in the presence of various aquifer materials, and (3) column experiments which were used to investigate permanganate transport in a system that mimics the subsurface environment. The long-term experiments which involved more than 180 batch reactors monitored for ~300 days showed that the unproductive permanganate consumption by aquifer materials or natural oxidant demand (NOD) is strongly affected by the initial permanganate concentration, permanganate to solid mass ratio, and the reductive components associated with each aquifer material. This consumption cannot be represented by an instantaneous reaction process but is kinetically controlled by at least a fast and slow reactive component. Accordingly, an empirical expression for permanganate NOD in terms of aquifer material properties, and a hypothetical kinetic model consisting of two reaction components were developed. In addition, a fast and economical permanganate NOD estimation procedure based on a permanganate COD test was developed and tested. The investigation into short-term permanganate consumption (time scale of hours) was based on the theoretical derivation of the stoichiometric reaction of permanganate with bulk aquifer material reductive components, and consisted of excess permanganate mass experiments and excess aquifer material mass experiments. The results demonstrated that permanganate consumption by aquifer materials can be characterized by a very fast reaction on the order of minutes to hours, confirming the existence of the fast reaction component of the hypothetical kinetic model used to describe the long-term permanganate NOD observations. A typical experimental column trial consisted of flushing an aquifer-material packed column with the permanganate source solution until sufficient permanganate breakthrough was observed. The permanganate column results indicated the presence of a fast and slow consumption rate consistent with the long-term batch test data, and an intermediate consumption rate affecting the shape of the rising limb of the breakthrough curve. Finally, a comparison of the experimental results between batch and column systems indicated that permanganate NOD was significantly overestimated by the batch experiments; however, permanganate consumption displayed some similarity between the batch and column systems and hence an empirical expression was developed to predict permanganate consumption in physically representative column systems from batch reactor data. <br /><br /> The interaction between hydrogen peroxide and aquifer materials was also investigated with both batch and column experiments. A series of batch experiments consisting of a mixture of 2% hydrogen peroxide and 15 g of aquifer materials was used to capture the overall hydrogen peroxide behavior in the presence of various aquifer materials. The results indicated that the decomposition of hydrogen peroxide in the presence of various aquifer materials followed a first-order rate law, and was strongly affected by the content of amorphous transition metals (i. e. , Fe and Mn). Although hydrogen peroxide decomposition is related to the total organic carbon (TOC) content of natural aquifer materials, the results from a two-week long exposure to hydrogen peroxide suggests that not all forms of natural organic matter contributed to this decomposition. A multiple linear regression analysis was used to generate predictive relationships to estimate hydrogen peroxide decomposition rate coefficients based on various aquifer material properties. The enhanced stability of hydrogen peroxide was investigated under six scenarios with the addition of chelating reagents. The impact of a new green chelating reagent, S,S'-ethylenediaminedisuccinate (EDDS), on the stability of hydrogen peroxide in the presence of aquifer materials was experimentally examined and compared to that of the traditional and widely used chelating reagent, Ethylenediaminetetraacetic (EDTA). The results demonstrated that EDDS was able to significantly increase the stability of hydrogen peroxide, especially for aquifer materials with low TOC contents and/or high dissolvable Fe and Mn contents. Finally, to complement and expand the findings from the batch experiments, column experiments were conducted with aquifer materials from five representative sites. Each column was flushed with two types of source solutions (with or without EDDS addition) at two flow rates. The column experiments showed that the use of EDDS resulted in an earlier breakthrough and a higher stable concentration of hydrogen peroxide relative to the case without the addition of EDDS. The hydrogen peroxide decomposition rate coefficients generated from the column data were significantly higher than those generated from the batch test data and no correlation between hydrogen peroxide decomposition coefficients obtained from column and batch experiments was observed. Based on the column experimental results, a one-dimensional transport model was also calibrated to capture the hydrogen peroxide breakthrough process. <br /><br /> Data from bench-scale tests are routinely used to support both ISCO design and site screening, and therefore the findings from this study can be used as guidance on the utility of these tests to generate reliable and useful information. In general, the behavior of both permanganate and hydrogen peroxide in the presence of aquifer materials in batch and the column systems clearly indicates that the use of batch test data for ISCO system design is questionable since column experiments are believed to mimic in situ conditions better since column systems provide more realistic aquifer material contact. Thus the scaling relationships developed in this study provide meaningful tools to transfer information obtained from batch systems, which are widely employed in most bench-scale studies, to column systems.

Pentaerythritol tetranitrate (PETN), a nitrate ester, is widely used as a powerful explosive and is classified as a munitions constituent of great concern by DoD in U.S.A. It is an environmental concern and poses a threat to ecosystem and human health. Our objective was to examine potential remediation strategies for both PETN-contaminated water and soil. Flow-through iron columns were used to determine the potential for using granular iron to degrade PETN in aqueous phase. PETN transformation in both a 100% iron column and a 30% iron and 70% silica sand column followed pseudo-first-order kinetics, with average half-lives of 0.26 and 1.58 minutes, respectively. Based on the identified intermediates and products, the reaction pathway was proposed to be a sequential denitration process, in which PETN was stepwisely reduced to pentaerythritol with the formation of pentaerythritol trinitrate (PETriN) and pentaerythritol dinitrate (PEDN). Although pentaerythrito mononitrate was not detected, an approximately 100% nitrogen mass recovery indicated that all nitro groups were removed from PETN. Nitrite was released in each denitration step and subsequently reduced to NH4+ by iron. Nitrate was not detected during the experiment, suggesting that hydrolysis was not involved in PETN degradation. Furthermore, batch experiments showed that PETN dissolution was likely a rate-limiting factor for PETN degradation, especially in the case with high amount of iron. Using 50% methanol as a representative co-solvent, PETN solubility was greatly enhanced and thus the removal efficiency was improved. The results demonstrate the use of granular iron to remediate PETN-contaminated water. The biodegradability of aqueous PETN was examined with a mixed microbial culture from a site contaminated with PETN. The mixed culture was enriched and selected using a mineral medium containing acetate and yeast extract as carbon and nutrient sources in the presence of nitrate or sulfate. The final enrichment cultures were used as inocula for studying PETN biodegradation under nitrate-reducing and sulfate-reducing conditions. In addition, PETN degradation was tested using the original microbial culture under the mixed electron acceptor conditions of nitrate and sulfate. The results showed that under all conditions tested, PETN was sequentially reduced, apparently following the same pathway as the abiotic reduction by granular iron. Pentaerythritol mononitrate, a suspected intermediate in the abiotic degradation by iron, was identified in this experiment. The presence of nitrate seemed not to affect the kinetics of PETN degradation, with both PETN and nitrate degrading simultaneously. However, the rate of nitrate reduction was much faster than PETN degradation. With respect to sulfate, its presence did not have an adverse effect on PETN degradation, indicated by the very similar degradation rates of PETN in the presence and absence of sulfate. Under all conditions, PETN appeared to act as a terminal electron acceptor for energy generation during biodegradation. A utilization sequence by bacteria in the order of nitrate, PETN, PETriN, PEDN and sulfate was clearly observed. The study in this phase demonstrated that under anaerobic conditions, with carbon sources provided, PETN can be effectively biodegraded by indigenous bacteria in contaminated soil, most likely by denitrifying bacteria. Based on the successful demonstration of abiotic and biotic degradation of PETN in the aqueous phase, both methods were further tested for remediating PETN-contaminated soil in both laboratory and pilot scale. In the laboratory, a systematic soil microcosm experiment was conducted using soil from a contaminated site and additions of either granular iron or organic materials, with deoxygenated Millipore water. Because of the high concentration in the contaminated soil, solid-phase of PETN was initially present in the microcosms. Two types of DARAMEND products, D6390Fe20 (containing 20% iron + 80% botanical materials) and ADM-298500 (100% botanical materials), were used as sources of carbon and other nutrients. During the 84-day incubation period, more than 98% was removed in all DARAMEND treatments, following pseudo-first-order kinetics with half-lives ranging between 8 and 18 days. The results clearly demonstrated that PETN can be effectively degraded under anaerobic conditions with the addition of carbon and possibly nutrients. As in the aqueous tests, the sequence of microbial utilization was nitrate followed by PETN and sulfate. In contrast to the tests with aqueous PETN, iron was not effective in removing PETN in the contaminated soil, due to iron passiviation caused by the presence of high levels of nitrate in the soil. In addition, a slight enhancement was observed in a combined system of iron and biodegradation over biodegradation only. However, the extent of enhancement is not believed to be significant relative to the extra cost for iron addition. A pilot scale test was conducted at a PETN-contaminated site at Louviers, CO, a waste pond which had received waste water from PETN manufacture for over 20 years. The test involved 10 treatments, one control without amendment, one amended with iron (10%), eight with different types and amounts of organic carbon (1%, 2% and 4% of D6390Fe20; 2% and 4% of ADM-298500 and 1%, 2% and 4% of brewers grain). Each treatment was performed in a plastic tub (45 cm wide × 90 cm long × 25 cm deep), containing approximately 18 cm thick layer of soil and 6-8 cm of standing water. Over 74 days, very little consistent reduction of PETN was found in the iron treatment, which was also due to iron passivation in the presence of nitrate in the soil. In contrast, significant removal of PETN (11,200 to 33,400 mg/kg) was observed in the treatments amended with organic materials, and the extent of removal increased with increasing amounts of organic materials. The pilot test was consistent with the results of the laboratory experiments for iron and biodegradation with carbon addition. For biological treatment, the stoichiometric estimation suggests that the complete remediation in many of the treatments will be ultimately limited by carbon sources. Results of this study showed the great potentials of using granular iron to degrade PETN in solution and using indigenous bacteria present in contaminated soils to biodegrade PETN in both the solution and soil phase. Both iron and biodegradation with carbon addition represent viable approaches for remediation of PETN-contaminated water and soil, though iron may not be appropriate in the presence of high concentration of nitrate.

Polychlorinated biphenyls (PCBs) are carcinogenic persistent contaminants. Although their manufacturing in North America ceased in the late 1970s, their high heat resistance made their use widespread over their production lifetime. As a result, PCB contamination has occurred globally and in particular has plague brownfield redevelopment in urban environments. The remediation of PCB contaminated soil or sediments has historically been dealt with through the expensive and unsustainable practice of excavation followed by off-site disposal or incineration. One potential technology that has shown some success with on-site remediation of PCB contamination is solvent extraction. Solvent extraction is technically simple; it involves excavating the contaminated soil, placing it in a vessel and adding solvent. The PCBs are extracted by the solvent and the treated soil is returned for use on site. Although successful at removing a large quantity of PCBs from some soils, this technology can be improved upon by extracting additional PCB mass and making the extraction more efficient and suitable for colder climates. This thesis aimed to identify the factors controlling PCB extraction with solvents in order to optimize PCB extraction as it is applied on different soil types and in various climates. The research investigated the impact of elevated moisture contents (≤ 20% by weight) on solvent extraction efficiency, the effects of low temperatures (<5ºC) on solvent extraction, and developed a kinetic model to represent PCB solvent extraction. As past research has shown, weathered PCB in soil is more difficult to remove. Contaminated field samples from Southern Ontario, Canada were used for this work, rather than synthetically prepared samples. The impact of elevated moisture contents and low temperature on extraction efficiency was determined through a series of screening experiments using polar and non-polar solvents at both 20ºC and 4ºC. It was hypothesized that improved extractions may be possible with combinations of polar and non-polar solvents. Based on the results of these screening experiments, a factorial experiment was designed using solvent combinations to further assess the role of moisture contents and low temperatures. The role of PCB mass distribution among grain sizes was also evaluated to see if optimization based on grain size separation is possible. Finally, experiments were performed to generate data suitable for the development of a kinetic model that incorporates key factors affecting solvent extraction. Four suitable solvents for solvent extraction in Ontario were identified through a literature review and these were used for this work: isopropyl alcohol (polar), ethanol (polar), triethylamine (non-polar) and isooctane (non-polar). Triethylamine outperformed isooctane and performed best on its own rather than in combination with polar solvents. An interaction between soil moisture content and choice of polar solvent (isopropyl alcohol versus ethanol) was established: a given polar solvent achieves optimal PCB extraction at a specific moisture content range. Temperature was also identified as significantly influencing PCB extraction. Although it was determined that PCBs were distributed unevenly amongst grain sizes, a simple relationship between grain size and fractional organic carbon or organic content was not found. A simple two-compartment kinetic model was developed which is suitable for predicting the PCB concentrations extracted up to 24 hours. The model incorporates both temperature and soil to solvent ratio in order to estimate PCB concentration extracted.

In situ chemical oxidation (ISCO) is a leading-edge technology for soil and groundwater remediation, and involves injecting a chemical oxidant (e. g. , permanganate, hydrogen peroxide, or persulfate) into the subsurface to deplete contaminant mass through oxidation. Since the delivery of the chosen oxidant to the target treatment zone must occur in situ, the interaction between the injected oxidant and the aquifer material is a key controlling factor for a successful ISCO application. While many published ISCO studies have focused on the interaction between an oxidant and target contaminants, many questions still remain on the interaction between a potential oxidant and the aquifer material. Through a series of bench-scale experiments with aquifer materials collected from 10 sites throughout North America, the research presented in this thesis provides insight into the interaction between these aquifer materials and two widely used ISCO oxidants; permanganate and hydrogen peroxide. <br /><br /> The investigation into the interaction between aquifer materials and permanganate consisted of three series of bench-scale experiments: (1) long-term batch experiments which were used to investigate permanganate consumption in response to fundamental geochemical properties of the aquifer materials, (2) short-term batch experiments which were designed to yield kinetic data that describe the behavior of permanganate in the presence of various aquifer materials, and (3) column experiments which were used to investigate permanganate transport in a system that mimics the subsurface environment. The long-term experiments which involved more than 180 batch reactors monitored for ~300 days showed that the unproductive permanganate consumption by aquifer materials or natural oxidant demand (NOD) is strongly affected by the initial permanganate concentration, permanganate to solid mass ratio, and the reductive components associated with each aquifer material. This consumption cannot be represented by an instantaneous reaction process but is kinetically controlled by at least a fast and slow reactive component. Accordingly, an empirical expression for permanganate NOD in terms of aquifer material properties, and a hypothetical kinetic model consisting of two reaction components were developed. In addition, a fast and economical permanganate NOD estimation procedure based on a permanganate COD test was developed and tested. The investigation into short-term permanganate consumption (time scale of hours) was based on the theoretical derivation of the stoichiometric reaction of permanganate with bulk aquifer material reductive components, and consisted of excess permanganate mass experiments and excess aquifer material mass experiments. The results demonstrated that permanganate consumption by aquifer materials can be characterized by a very fast reaction on the order of minutes to hours, confirming the existence of the fast reaction component of the hypothetical kinetic model used to describe the long-term permanganate NOD observations. A typical experimental column trial consisted of flushing an aquifer-material packed column with the permanganate source solution until sufficient permanganate breakthrough was observed. The permanganate column results indicated the presence of a fast and slow consumption rate consistent with the long-term batch test data, and an intermediate consumption rate affecting the shape of the rising limb of the breakthrough curve. Finally, a comparison of the experimental results between batch and column systems indicated that permanganate NOD was significantly overestimated by the batch experiments; however, permanganate consumption displayed some similarity between the batch and column systems and hence an empirical expression was developed to predict permanganate consumption in physically representative column systems from batch reactor data. <br /><br /> The interaction between hydrogen peroxide and aquifer materials was also investigated with both batch and column experiments. A series of batch experiments consisting of a mixture of 2% hydrogen peroxide and 15 g of aquifer materials was used to capture the overall hydrogen peroxide behavior in the presence of various aquifer materials. The results indicated that the decomposition of hydrogen peroxide in the presence of various aquifer materials followed a first-order rate law, and was strongly affected by the content of amorphous transition metals (i. e. , Fe and Mn). Although hydrogen peroxide decomposition is related to the total organic carbon (TOC) content of natural aquifer materials, the results from a two-week long exposure to hydrogen peroxide suggests that not all forms of natural organic matter contributed to this decomposition. A multiple linear regression analysis was used to generate predictive relationships to estimate hydrogen peroxide decomposition rate coefficients based on various aquifer material properties. The enhanced stability of hydrogen peroxide was investigated under six scenarios with the addition of chelating reagents. The impact of a new green chelating reagent, S,S'-ethylenediaminedisuccinate (EDDS), on the stability of hydrogen peroxide in the presence of aquifer materials was experimentally examined and compared to that of the traditional and widely used chelating reagent, Ethylenediaminetetraacetic (EDTA). The results demonstrated that EDDS was able to significantly increase the stability of hydrogen peroxide, especially for aquifer materials with low TOC contents and/or high dissolvable Fe and Mn contents. Finally, to complement and expand the findings from the batch experiments, column experiments were conducted with aquifer materials from five representative sites. Each column was flushed with two types of source solutions (with or without EDDS addition) at two flow rates. The column experiments showed that the use of EDDS resulted in an earlier breakthrough and a higher stable concentration of hydrogen peroxide relative to the case without the addition of EDDS. The hydrogen peroxide decomposition rate coefficients generated from the column data were significantly higher than those generated from the batch test data and no correlation between hydrogen peroxide decomposition coefficients obtained from column and batch experiments was observed. Based on the column experimental results, a one-dimensional transport model was also calibrated to capture the hydrogen peroxide breakthrough process. <br /><br /> Data from bench-scale tests are routinely used to support both ISCO design and site screening, and therefore the findings from this study can be used as guidance on the utility of these tests to generate reliable and useful information. In general, the behavior of both permanganate and hydrogen peroxide in the presence of aquifer materials in batch and the column systems clearly indicates that the use of batch test data for ISCO system design is questionable since column experiments are believed to mimic in situ conditions better since column systems provide more realistic aquifer material contact. Thus the scaling relationships developed in this study provide meaningful tools to transfer information obtained from batch systems, which are widely employed in most bench-scale studies, to column systems.

Pentaerythritol tetranitrate (PETN), a nitrate ester, is widely used as a powerful explosive and is classified as a munitions constituent of great concern by DoD in U.S.A. It is an environmental concern and poses a threat to ecosystem and human health. Our objective was to examine potential remediation strategies for both PETN-contaminated water and soil. Flow-through iron columns were used to determine the potential for using granular iron to degrade PETN in aqueous phase. PETN transformation in both a 100% iron column and a 30% iron and 70% silica sand column followed pseudo-first-order kinetics, with average half-lives of 0.26 and 1.58 minutes, respectively. Based on the identified intermediates and products, the reaction pathway was proposed to be a sequential denitration process, in which PETN was stepwisely reduced to pentaerythritol with the formation of pentaerythritol trinitrate (PETriN) and pentaerythritol dinitrate (PEDN). Although pentaerythrito mononitrate was not detected, an approximately 100% nitrogen mass recovery indicated that all nitro groups were removed from PETN. Nitrite was released in each denitration step and subsequently reduced to NH4+ by iron. Nitrate was not detected during the experiment, suggesting that hydrolysis was not involved in PETN degradation. Furthermore, batch experiments showed that PETN dissolution was likely a rate-limiting factor for PETN degradation, especially in the case with high amount of iron. Using 50% methanol as a representative co-solvent, PETN solubility was greatly enhanced and thus the removal efficiency was improved. The results demonstrate the use of granular iron to remediate PETN-contaminated water. The biodegradability of aqueous PETN was examined with a mixed microbial culture from a site contaminated with PETN. The mixed culture was enriched and selected using a mineral medium containing acetate and yeast extract as carbon and nutrient sources in the presence of nitrate or sulfate. The final enrichment cultures were used as inocula for studying PETN biodegradation under nitrate-reducing and sulfate-reducing conditions. In addition, PETN degradation was tested using the original microbial culture under the mixed electron acceptor conditions of nitrate and sulfate. The results showed that under all conditions tested, PETN was sequentially reduced, apparently following the same pathway as the abiotic reduction by granular iron. Pentaerythritol mononitrate, a suspected intermediate in the abiotic degradation by iron, was identified in this experiment. The presence of nitrate seemed not to affect the kinetics of PETN degradation, with both PETN and nitrate degrading simultaneously. However, the rate of nitrate reduction was much faster than PETN degradation. With respect to sulfate, its presence did not have an adverse effect on PETN degradation, indicated by the very similar degradation rates of PETN in the presence and absence of sulfate. Under all conditions, PETN appeared to act as a terminal electron acceptor for energy generation during biodegradation. A utilization sequence by bacteria in the order of nitrate, PETN, PETriN, PEDN and sulfate was clearly observed. The study in this phase demonstrated that under anaerobic conditions, with carbon sources provided, PETN can be effectively biodegraded by indigenous bacteria in contaminated soil, most likely by denitrifying bacteria. Based on the successful demonstration of abiotic and biotic degradation of PETN in the aqueous phase, both methods were further tested for remediating PETN-contaminated soil in both laboratory and pilot scale. In the laboratory, a systematic soil microcosm experiment was conducted using soil from a contaminated site and additions of either granular iron or organic materials, with deoxygenated Millipore water. Because of the high concentration in the contaminated soil, solid-phase of PETN was initially present in the microcosms. Two types of DARAMEND products, D6390Fe20 (containing 20% iron + 80% botanical materials) and ADM-298500 (100% botanical materials), were used as sources of carbon and other nutrients. During the 84-day incubation period, more than 98% was removed in all DARAMEND treatments, following pseudo-first-order kinetics with half-lives ranging between 8 and 18 days. The results clearly demonstrated that PETN can be effectively degraded under anaerobic conditions with the addition of carbon and possibly nutrients. As in the aqueous tests, the sequence of microbial utilization was nitrate followed by PETN and sulfate. In contrast to the tests with aqueous PETN, iron was not effective in removing PETN in the contaminated soil, due to iron passiviation caused by the presence of high levels of nitrate in the soil. In addition, a slight enhancement was observed in a combined system of iron and biodegradation over biodegradation only. However, the extent of enhancement is not believed to be significant relative to the extra cost for iron addition. A pilot scale test was conducted at a PETN-contaminated site at Louviers, CO, a waste pond which had received waste water from PETN manufacture for over 20 years. The test involved 10 treatments, one control without amendment, one amended with iron (10%), eight with different types and amounts of organic carbon (1%, 2% and 4% of D6390Fe20; 2% and 4% of ADM-298500 and 1%, 2% and 4% of brewers grain). Each treatment was performed in a plastic tub (45 cm wide × 90 cm long × 25 cm deep), containing approximately 18 cm thick layer of soil and 6-8 cm of standing water. Over 74 days, very little consistent reduction of PETN was found in the iron treatment, which was also due to iron passivation in the presence of nitrate in the soil. In contrast, significant removal of PETN (11,200 to 33,400 mg/kg) was observed in the treatments amended with organic materials, and the extent of removal increased with increasing amounts of organic materials. The pilot test was consistent with the results of the laboratory experiments for iron and biodegradation with carbon addition. For biological treatment, the stoichiometric estimation suggests that the complete remediation in many of the treatments will be ultimately limited by carbon sources. Results of this study showed the great potentials of using granular iron to degrade PETN in solution and using indigenous bacteria present in contaminated soils to biodegrade PETN in both the solution and soil phase. Both iron and biodegradation with carbon addition represent viable approaches for remediation of PETN-contaminated water and soil, though iron may not be appropriate in the presence of high concentration of nitrate.

Polychlorinated biphenyls (PCBs) are carcinogenic persistent contaminants. Although their manufacturing in North America ceased in the late 1970s, their high heat resistance made their use widespread over their production lifetime. As a result, PCB contamination has occurred globally and in particular has plague brownfield redevelopment in urban environments. The remediation of PCB contaminated soil or sediments has historically been dealt with through the expensive and unsustainable practice of excavation followed by off-site disposal or incineration. One potential technology that has shown some success with on-site remediation of PCB contamination is solvent extraction. Solvent extraction is technically simple; it involves excavating the contaminated soil, placing it in a vessel and adding solvent. The PCBs are extracted by the solvent and the treated soil is returned for use on site. Although successful at removing a large quantity of PCBs from some soils, this technology can be improved upon by extracting additional PCB mass and making the extraction more efficient and suitable for colder climates. This thesis aimed to identify the factors controlling PCB extraction with solvents in order to optimize PCB extraction as it is applied on different soil types and in various climates. The research investigated the impact of elevated moisture contents (≤ 20% by weight) on solvent extraction efficiency, the effects of low temperatures (<5ºC) on solvent extraction, and developed a kinetic model to represent PCB solvent extraction. As past research has shown, weathered PCB in soil is more difficult to remove. Contaminated field samples from Southern Ontario, Canada were used for this work, rather than synthetically prepared samples. The impact of elevated moisture contents and low temperature on extraction efficiency was determined through a series of screening experiments using polar and non-polar solvents at both 20ºC and 4ºC. It was hypothesized that improved extractions may be possible with combinations of polar and non-polar solvents. Based on the results of these screening experiments, a factorial experiment was designed using solvent combinations to further assess the role of moisture contents and low temperatures. The role of PCB mass distribution among grain sizes was also evaluated to see if optimization based on grain size separation is possible. Finally, experiments were performed to generate data suitable for the development of a kinetic model that incorporates key factors affecting solvent extraction. Four suitable solvents for solvent extraction in Ontario were identified through a literature review and these were used for this work: isopropyl alcohol (polar), ethanol (polar), triethylamine (non-polar) and isooctane (non-polar). Triethylamine outperformed isooctane and performed best on its own rather than in combination with polar solvents. An interaction between soil moisture content and choice of polar solvent (isopropyl alcohol versus ethanol) was established: a given polar solvent achieves optimal PCB extraction at a specific moisture content range. Temperature was also identified as significantly influencing PCB extraction. Although it was determined that PCBs were distributed unevenly amongst grain sizes, a simple relationship between grain size and fractional organic carbon or organic content was not found. A simple two-compartment kinetic model was developed which is suitable for predicting the PCB concentrations extracted up to 24 hours. The model incorporates both temperature and soil to solvent ratio in order to estimate PCB concentration extracted.

Petroleum hydrocarbons (PHCs) such as gasoline are ubiquitous organic compounds present at contaminated sites throughout the world. Accidental spills and leakage from underground storage tanks results in the formation of PHC source zones that release hundreds of organic compounds, including the high impact, acutely toxic and highly persistent aromatics (e.g., benzene, toluene, ethylbenzene, xylenes, trimethylbenzenes and naphthalene) into groundwater. Contamination by these compounds continues to persist until the PHC source zone is treated in place or removed. In situ chemical oxidation (ISCO) employing persulfate was identified as a potentially viable technology for the treatment of PHC source zones. The effectiveness and efficiency and, therefore, the overall economic feasibility of a persulfate-based ISCO treatment system depend upon the reactivity of the target organic compounds and the interaction of persulfate with aquifer media. The objective of this research was to investigate the persistence of unactivated and activated persulfate in the presence of aquifer materials, and to examine persulfate oxidation of PHC compounds at both the bench- and pilot-scales. A series of bench-scale studies were performed to estimate persulfate degradation kinetic parameters in the presence of seven well-characterized, uncontaminated aquifer materials and to quantify the changes in specific properties of these materials. Batch experiments were conducted in an experimental system containing 100 g of solids and 100 mL of persulfate solution at 1 or 20 g/L. Column experiments were designed to mimic in situ conditions with respect to oxidant to solids mass ratio and were performed in a stop-flow mode using a 1 g/L persulfate solution. The degradation of persulfate followed a first-order rate law for all aquifer materials investigated. An order of magnitude decrease in reaction rate coefficients was observed for systems that used a persulfate concentration of 20 g/L as compared to those that used 1 g/L due to ionic strength effects. As expected, the column experiments yielded higher reaction rate coefficients than batch experiments for the same persulfate concentration due to the lower oxidant to solids mass ratio. Bench-scale data was used to develop a kinetic model to estimate the kinetic response of persulfate degradation during these tests. The push-pull tests involved the injection of persulfate (1 or 20 g/L) and a conservative tracer into a hydraulically isolated portion of the sandy aquifer at CFB Borden, Canada. The kinetic model developed from the bench-scale data was able to reproduce the observed persulfate temporal profiles from these push-pull tests. This implies that persulfate degradation kinetics is scalable from bench-scale to in situ scale, and bench tests can be employed to anticipate in situ degradation. The estimated reaction rate coefficients indicate that persulfate is a persistent oxidant for the range of aquifer materials explored with half lives ranging from 2 to 600 days, and therefore in situ longevity of persulfate will permit advective and diffusive transport in the subsurface. This is critical for successful delivery of oxidant to dispersed residuals in the subsurface. Activation of persulfate is generally recommended to enhance its oxidation potential and reactivity towards organic compounds. This approach may influence the stability of persulfate-activator system in the presence of aquifer materials. A series of batch tests were performed to investigate persistence of persulfate at two concentrations (1 or 20 g/L) using three contemporary activation strategies (citric acid chelated-ferrous, peroxide and high pH ) in the presence of 4 well-characterized, uncontaminated aquifer materials. Chelation by citric acid was ineffective in controlling the interaction between persulfate and Fe(II) and a rapid loss in persulfate concentration was observed. Higher Fe(II) concentration (600 mg/L) led to greater destabilization of persulfate than lower Fe(II) concentration (150 mg/L) and the persulfate loss was stoichiometrically equivalent to the Fe(II) concentration employed. Subsequent to this rapid loss of persulfate, first-order degradation rate coefficients (kobs) were estimated which were up to 4 times higher than the unactivated case due to the interaction with Fe(III) and CA. Total oxidation strength (TOS) was measured for peroxide activation experiments and was observed to decrease rapidly at early time due peroxide degradation. This was followed by slow degradation kinetics similar to that of unactivated persulfate implying that the initial TOS degradation was peroxide dominated and the long-term kinetics were dominated by persulfate degradation. The kobs used to capture TOS degradation for later time were shown to depend upon unactivated persulfate and peroxide degradation rate coefficients, and peroxide concentration. Either a slow peroxide degradation rate and/or higher peroxide concentration allow a longer time for peroxide and persulfate to interact which led to kobs ~1 to 100 times higher than kobs for unactivated persulfate. For alkaline activation, kobs were only 1 to 4 times higher than unactivated persulfate and therefore alkaline conditions demonstrated the least impact on persulfate degradation among the various activation strategies used. For all activation trials, lower stability of persulfate was observed at 1 g/L as compared to 20 g/L due to insufficient persulfate and/or ionic strength effects. A series of batch reactor trials were designed to observe the behavior of the nine high impact gasoline compounds and the bulk PHC fraction measures subjected to various persulfate activation strategies over a 28-day period. This bench-scale treatability used unactivated persulfate (1 or 20 g/L) and activated persulfate (20 g/L). Activation employed chelated-Fe(II), peroxide, high pH or two aquifer materials as activators. No significant oxidation of the monitored compounds was observed for unactivated persulfate at 1 g/L, but 20 g/L persulfate concentration resulted in their near-complete oxidation. Oxidation rates were enhanced by 2 to 18 times by activation with peroxide or chelated-Fe(II). For alkaline activation, pH 11 trials demonstrated ~2 times higher oxidation rates than the unactivated results. For pH 13 activation the oxidation rates of benzene, toluene and ethylbenzene were reduced by 50% while for the remaining monitored compounds they were enhanced by 5 to 100%. Natural activation by both aquifer materials produced oxidation rates similar to the unactivated results, implying that either activation by minerals associated with aquifer material was not significant or that any potential activation was offset by radical scavenging from aquifer material constituents. Acid-catalyzation at pH <3 may enhance oxidation rates in weakly buffered systems. Oxidation of the monitored compounds followed first-order reaction kinetics and rate coefficients were estimated for all the trials. Overall, activated and unactivated persulfate appear to be suitable for in situ treatment of gasoline. Persulfate under unactivated or naturally activated conditions demonstrated significant destruction of gasoline compounds and showed higher persulfate persistence when in contact with aquifer solids as compared to chelated-Fe(II) or peroxide-activated persulfate systems. This observation was used as the basis for selecting unactivated sodium persulfate for a pilot-scale treatment of gasoline-contaminated source zone at CFB Borden, Canada where a ~2000 L solution of persulfate (20 g/L) was injected into a PHC source zone. Concentration of organics and inorganics were frequently monitored over a 4 month period across a 90 point monitoring fence line installed down-gradient. Treatment performance was measured by estimating organic and inorganic mass loading across the monitoring fence. Increased mass loading for sodium was observed over time as the treatment volume moved across the fence-line indicating transport of the inorganic slug created upon oxidant injection. The mass loading also increased for sulfate which is a by-product generated either due to persulfate degradation during oxidation of organic compounds or during its interaction with aquifer materials. Oxidation of organic compounds was evident from the enhanced mass loading of dissolved carbon dioxide. More importantly, a significant (45 to 86%) decrease in mass loading of monitored compounds was observed due to oxidation by injected persulfate. The cumulative mass crossing the monitoring fence-line was 20 to 50% lower than that expected without persulfate treatment. As the inorganic slug was flushed through the source zone and beyond the monitoring fence, the mass loading rate of sodium, sulfate and carbon dioxide decreased and approached background condition. Mass loading of the monitored compounds increased to within 40 to 80% of the pre-treatment conditions, suggesting partial rebound. These investigations assessed the impact of activation on persulfate persistence and treatability of gasoline and served to establish guidelines for anticipating field-scale persulfate behavior under similar conditions. In summary, unactivated persulfate is a stable oxidant in the presence of aquifer materials and its persistence depends upon TOC and Fe(Am) content of the materials, ionic strength, and aquifer to solids mass ratio. Persulfate exhibits significant destruction of gasoline compounds and can be employed for the remediation of gasoline-contaminated sites. Peroxide and chelated-Fe(II) enhance oxidation rates of these compounds, but reduce stability of the persulfate-activator system. Persulfate activation using high pH conditions does not significantly impact persulfate persistence but reduces the overall destruction of gasoline compounds. Therefore, activation imposes a trade-off between enhanced oxidation rates and reduced persulfate persistence. Kinetic model is representative of persulfate degradation at bench- and pilot-scales and can be used for estimation of in situ degradation. The quantification of oxidation rates for gasoline compounds under activated and unactivated persulfate conditions will assist decision-making for identification of appropriate remediation options when targeting contamination by gasoline or by specific high impact gasoline compounds. While persulfate oxidation resulted in partial treatment of a small gasoline source zone, aggressive persulfate load will be required during injection for a complete clean-up. Overall, persulfate-based in situ chemical oxidation was demonstrated to be an effective and a viable technology for the remediation of contaminated soil and groundwater.

Degassing and in situ formation of a mobile gas phase takes place when an aqueous phase equilibrated with a gas at a pressure higher than the subsurface pressure is injected in water-saturated porous media. This process, which has been termed supersaturated water injection (SWI), is a novel and hitherto unexplored means of introducing a gas phase into the subsurface. Herein is a first macroscopic account of the SWI process on the basis of continuum scale simulations and column experiments with CO2 as the dissolved gas. A published empirical mass transfer correlation (Nambi and Powers, Water Resour Res, 2003) is found to adequately describe the non-equilibrium transfer of CO2 between the aqueous and gas phases. Remarkably, the dynamics of gas-water two-phase flow, observed in a series of SWI experiments in homogeneous columns packed with silica sand or glass beads, are accurately predicted by traditional two-phase flow theory which allows the corresponding gas phase relative permeability to be determined. A key consequence of the finding, that the displacement of the aqueous phase by gas is compact at the macroscopic scale, is consistent with pore scale simulations of repeated mobilization, fragmentation and coalescence of large gas clusters (i.e., large ganglion dynamics) driven entirely by mass transfer. The significance of this finding for the efficient delivery of a gas phase below the water table in relation to the alternative process of in-situ air sparging and the potential advantages of SWI are discussed. SWI has been shown to mobilize a previously immobile oil phase in the subsurface of 3-phase systems (oil, water and gas). A macroscopic account of the SWI process is given on the basis of continuum-scale simulations and column experiments using CO2 as the dissolved gas and kerosene as the trapped oil phase. Experimental observations show that the presence of oil ganglia in the subsurface alters gas phase mobility from 2-phase predictions. A corresponding 3-phase gas relative permeability function is determined, whereas a published 3-phase relative permeability correlation (Stone, Journal of Cana Petro Tech, 1973) is found to be inadequate for describing oil phase flow during SWI. A function to predict oil phase relative permeability is developed for use during SWI at high aqueous phase saturations with a disconnected oil phase and quasi-disconnected gas phase. Remarkably, the dynamics of gas-water-oil 3-phase flow, observed in a series of SWI experiments in homogeneous columns packed with silica sand or glass beads, are accurately predicted by traditional continuum-scale flow theory. The developed relative permeability function is compared to Stone’s Method and shown to approximate it in all regions while accurately describing oil flow during SWI. A published validation of Stone’s Method (Fayers and Matthews, Soc of Petro Eng Journal, 1984) is cited to validate this approximation of Stone’s Method.

The efficacy of injection-driven remediation techniques for non-aqueous phase liquid (NAPL) source zones is limited by the principle that fluid flow is focused along paths of least hydraulic resistance. The pressure pulse technology stands among a number of innovative methods that have been developed with the aim of overcoming or mitigating this limitation. The objective of this research was to observe and document differences in saturated groundwater flow and solute transport between an injection using a conventional or continuous pressure delivery approach and an injection using a pressure pulsing instrument. The underlying motivation was to identify engineering opportunities presented by pressure pulsing with the potential to improve remediation efficiency at contaminated sites. A series of tracer injections were conducted in the unconfined aquifer at the University of Waterloo Groundwater Research Facility at Canadian Forces Base (CFB) Borden near Alliston, ON (homogeneous fine sand), and in the shallow aquifer at a groundwater research site located on the North Campus at the University of Waterloo (moderately heterogeneous with discrete layers varying from fine sand to silt). A single injection well was used at each site for both the conventional and pressure pulsing injections. Different tracers were used for consecutive injections. Bromide, Lithium, Chloride, and fluorescent dyes (Rhodamine WT and Sulforhodamine B) were used. Formation pressurization data was captured by pressure transducers. The spatial distribution of the injected tracers was monitored at a series of multilevel wells. A groundwater flow and solute transport modeling exercise (MODFLOW and MT3DMS numerical engines) simulating the rapid boundary pressure modulation that occurs in association with pressure pulsing was conducted to complement the field injections. A two-dimensional domain was used to conduct a parametric investigation of pressure modulation and its effect on flow and transport. A three-dimensional domain served to scale-up the two-dimensional results and for benchmarking against field observations. Pressure pulsing simulation results reveal that repeated sudden onset of injection cessation produces brief periods of gradient reversal near the injection well and the development of a mixing zone around the injection well. The spatial extents of this mixing zone are highly dependent upon the hydraulic diffusivity of the medium. Greater heterogeneity in combination with presence of high hydraulic diffusivity pathways maximized the extent of the mixing zone and the magnitude of transverse and reversal hydraulic gradients. Lower pulsing frequency and higher pulsing amplitude favoured a more significant mixing zone, though these effects were secondary to geologic properties. Use of the pressure pulsing tool did not manifest into distinct changes in tracer breakthrough at either field research site. Comparison between tracer tests was complicated by sorption of fluorescent dyes and ongoing well development. Solute transport simulation results demonstrated augmentation of dispersion arising from the mixing zone phenomenon, but no distinct changes in advection.