The ability of supersaturated water injection (SWI) to recover non-aqueous phase liquids (NAPLs) was studied at the field scale as part of an ongoing program to evaluate its applicability to groundwater remediation. SWI uses Gas inFusionTM technology to efficiently dissolve gases into liquids at elevated pressures. SWI has been shown to both volatilize and mobilize residual NAPL ganglia (Li, 2004). During SWI pressurized water containing high concentrations of CO2 is injected into the subsurface below the zone of contamination. Once the injected water is in the aquifer the pressure drops substantially and the concentration of CO2 is no longer in equilibrium with the water and as a result CO2 bubbles nucleate. These bubbles then migrate upwards through the contaminated zone towards the water table. As they move they come into contact with residual NAPL ganglia and they either volatilize this NAPL, resulting in a bubble comprised of CO2 and gaseous NAPL, or mobilize this NAPL, resulting in a film of NAPL surrounding the bubble. In either case the bubbles continue to rise until they reach the water table at which point they are removed by a dual phase extraction system. In this work, a known amount of NAPL was emplaced below the water table at residual concentrations to represent a residual source of weathered gasoline. The source was created in a hydraulically isolated cell in an unconfined sand aquifer at CFB Borden, Ontario. After the source was emplaced SWI was used to remove as much of the contaminant mass as possible in 22.25 days of operation over three months. The goal of this project was to determine if SWI was capable of removing residual NAPL at a field site. It was successful in removing volatile NAPL but not non-volatile NAPL. 64% of the volatile compounds were removed but contaminant mass was still being removed when the system was shut down so with continued operation more mass would have been removed. There is no way of knowing how much more would have been removed had the project continued. These results indicate that continued development of the technology is warranted.

In order to preserve groundwater as a viable source of drinking water, remedial measures must be applied where appropriate. The application of the various remedial technologies is site and contaminant dependent. Differing geology, subsurface soil, groundwater geochemistry, type of contaminant present, cost and even accessibility to the site are all considerations when selecting an appropriate remedial system. At many sites oxygen is a limiting factor for aerobic degradation of many organic compounds like methyl tert butyl ether (MTBE) and hydrocarbons found in diesel and fuel oil, etc. (Nyer et al, 2002). Mechanisms limiting the success of getting the oxygen out of the passive release well include: · Slow chemical diffusion of oxygen in water; · Limited cross section of the groundwater flowing into the well and advecting oxygenated water back into the aquifer; and · Generally weak transverse dispersion, both horizontal and vertical, during subsequent advection of the oxygenated water in the porous media. These issues must be recognized even in the design of a passive release well remediation system. For example, a typical remedial objective is to deliver dissolved oxygen across the width and vertical extent of a contaminant zone in an aquifer. The width of the oxygen plume around the injection well defines how many oxygen-release wells are required to create a curtain of oxygen. Cost-effective design dictates fewer wells, while effective coverage may dictate more wells placed closer together. Thus, understanding the transverse width over which significant oxygen is passively released to the aquifer (the “radius of influence”) is a critical design parameter and the focus of this thesis. Due to the difficulty in getting a passively released dissolved oxygen plume to transversely encompass the total width of a contaminant plume, other more efficient means of introducing oxygen into the subsurface are required. Injecting amended water directly into a release well would increase the transverse distance in which dissolved oxygen would spread. A series of experiments were conducted at CFB Borden to assess the efficacy of an oxygen releasing technology called the iSOC™. The experiments were all conducted in the same manner, by connecting a tank of oxygen to the iSOC™ unit, which then was placed in a release well and allowed to run in experiment 1 for 103 days, experiment 2 for 132 days and experiment 3 for 29 days. iv Dissolved oxygen concentrations were measured at varying time intervals throughout each experiment using an Orion dissolved oxygen probe. Results of each of the three experiments were very similar in that dissolved oxygen was only detected in a very narrow plume (10 cm to 25 cm in width) within 1 m of the release well. The presence of BTEX, BOD and COD within the groundwater and soil at the site were investigated to assess if presented a significant enough sink for the oxygen and thereby limiting the transverse growth of the dissolved oxygen plume. Groundwater results indicated that while dissolved oxygen was utilized for BTEX degradation and to overcome the natural oxygen demand (both BOD and COD) at the site, the amount of oxygen released into the aquifer would have satisfied both of these processes. The COD of the soil at the site presented a higher oxygen demand than the groundwater and presented a greater limiting factor to the transverse growth of the oxygen plume. By releasing oxygen passively with the iSOC™ only a small transverse portion of the Borden aquifer was likely influenced. This limitation has been noted in general for passive release technologies (Wilson & Mackay, 1995). While the iSOCÔ technology develops very high oxygen levels in the groundwater in the release well, it does not overcome the hydrogeological constraint of limited transverse dispersion. Thus, a high oxygen concentration is delivered to a very narrow segment of the aquifer. Overall, transverse dispersion has a minimal impact on a passively release oxygen plume, particularly in close proximity to the release well, but once the plume has migrated a distance away from the release well the effect of transverse dispersion increases. The oxygen demand of an aquifer can also limit the effect of transverse and longitudinal dispersion. If a site has a high chemical or biological oxygen demand the released gas will be consumed before dispersion can have an effect on the plume. By injecting nutrient rich water into a release well the water will forcibly overcome any influence transverse dispersion will have in and around a release well, thereby relying on longitudinal dispersion to create a larger area for contaminant degradation to occur.

Water quality degradation is the foremost environmental issue faced by the mining industry. Negative impacts on water quality are commonly associated with unmitigated drainage emanating from sulfide-bearing mine waste deposits. These impacts stem from the liberation of acidity, sulfate, metals (e.g. Fe, Ni, Cu, Zn and Pb), and trace elements (e.g. Co, As, Cd, Sb and Tl) during the oxidation of sulfide minerals. Drainage at operational mines is commonly treated using techniques such as chemical oxidation and acid neutralization, which can succeed in achieving regulatory discharge guidelines. However, active treatment techniques are commonly burdened by high capital and operating costs. The development of passive technologies for treatment of mine drainage, which promote sulfate reduction, metal-sulfide precipitation and alkalinity production, therefore present a cost-effective alternative for managing mine drainage quality. This thesis describes laboratory and field evaluations of techniques for passive in situ treatment of acidic and neutral mine waters. Laboratory batch experiments evaluated the treatment of acid mine drainage (AMD) with mixtures of organic carbon and zero-valent iron (ZVI) for use in permeable reactive barriers (PRBs). Modest increases in sulfate-reduction rates up to 15 % were achieved by amending organic carbon mixtures with 5 to 10 % (dry wt.) ZVI. Reactive mixtures containing organic carbon supported growth of sulfate-reducing bacteria (SRB) and facilitated removal of Fe, Zn, Cd, Ni, Co and Pb. However, organic carbon was necessary to support SRB growth and sulfate reduction. Removal of Zn, Cd, Ni, Co and Pb in the absence of organic carbon is attributed to sorption and (co)precipitation reactions at the ZVI surface. Scanning electron microscopy (SEM) and X-ray absorption near-edge structure (XANES) spectroscopy confirmed the presence of secondary Fe-sulfides in mixtures containing organic carbon. The dominant reaction product in these mixtures was identified as disordered mackinawite [Fe1+xS]. The addition of ZVI to organic carbon enhanced AMD treatment over the duration of this experiment; however, long-term evaluation is required to identify optimal reactive mixtures. Field-based investigations into passive management of near-neutral pH tailings pore-water were carried out at the Greens Creek mine, located near Juneau, Alaska, USA. These studies focused on delineation of mechanisms controlling tailings pore-water chemistry, and a evaluation of the effectiveness of organic carbon amendment of tailings for passive in situ management of pore-water quality. Results demonstrate that sulfide-mineral oxidation and carbonate dissolution are the primary influences on tailings pore-water composition. Pyrite [FeS2] accounted for < 20 to > 35 wt. % of the tailings mineral assemblage, whereas dolomite [CaMg(CO3)2] and calcite [CaCO3] were present at ≤ 30 and 3 wt. %, respectively. The sulfide-mineral assemblage was dominated by pyrite; however, sphalerite [(Zn,Fe)S] and galena [PbS] were commonly observed, and tetrahedrite [(Fe,Zn,Cu,Ag)12Sb4S13], arsenopyrite [FeAsS], and chalcopyrite [CuFeS2] were present in lesser amounts. Geochemical analysis of tailings core samples generally agreed with mineralogical data. The occurrence of Cd, Cr, Co, Mo, Ni, Se, and Tl is attributed to their occurrence as impurities in primary sulfide phases. Most probable number (MPN) populations of neutrophilic sulfur-oxidizing bacteria (nSOB) and SRB were elevated at several locations within the tailings deposit. Near-neutral pH conditions dominated; however, elevated concentrations of dissolved SO4, S2O3, Fe, Zn, As, Sb, and Tl were observed within and below the oxidation zone. Field-scale experiments conducted over four years evaluated passive in situ treatment of pore-water by amending unoxidized tailings with 5 and 10 vol. % organic carbon. Field-scale cells were constructed to evaluate amendments containing differing mixtures of peat, dried spent brewing grain (SBG), and municipal biosolids (MB). Organic carbon amendment of the tailings supported the development of conditions favorable to sulfate reduction. Decreases in aqueous SO4 concentrations were observed in three cells amended with mixtures of peat, SBG, and MB. Removal of SO4 was generally accompanied by H2S production, enrichment in 34S-SO4, and increased SRB populations. Undersaturation of pore-water with respect to gypsum was observed. Sulfate reduction was sustained for the duration of the experiment in cells amended with 5 vol. % peat + SBG and 10 vol. % peat + SBG + MB. The addition of organic carbon also supported reductive dissolution of Fe(III) (oxy)hydroxides and mobilization of Fe and As. The largest increases in aqueous Fe and As concentrations were observed in cells amended with MB. Subsequent decreases in Fe and As concentrations were observed under sulfate-reducing conditions. Attenuation of Zn, Sb, and Tl accompanied SO4 removal. Mineralogical examination by SEM revealed the presence of secondary Zn-S and Fe-S precipitates on surfaces of organic carbon particles, and carbonate and aluminosilicate grains. This study demonstrates that amendment of tailings with a small and dispersed mass of organic carbon has potential to improve the quality of tailings pore water.

Petroleum hydrocarbon (PHC) contamination poses a serious threat to aquifer systems worldwide. Accidental releases of PHCs due to gasoline spills and leakage from underground storage tanks can often result in PHC subsurface contamination. The main compounds of concern associated with gasoline spills are benzene, toluene, ethylbenzene and xylenes (BTEX), trimethylbenzenes (TMBs) and naphthalene, due to their high mobility and potential human health risks. Sodium persulphate is one of the newest oxidants to gain widespread use for in situ chemical oxidation (ISCO), however its effectiveness in treating PHCs is not fully understood. In this study, the ability to use unactivated sodium persulphate as a remediation tool in treating dissolved and residual BTEX contamination was tested during a bench-scale laboratory study and within a pilot-scale field investigation. In both cases unactivated sodium persulphate was used at a concentration of 100 g/L. A laboratory-scale degradation potential batch test was conducted to assess the efficacy of unactivated sodium persulphate to oxidize petroleum hydrocarbon contaminated groundwater in conjunction with aquifer material from a field site. Data from the control reactions indicated that persulphate was stable for the entire 35-day experimental period and that the decrease in PHC concentrations for most of the samples followed a first-order degradation. The behaviour and ability for sodium persulphate to oxidize dissolved and residual BTEX contamination was further evaluated in a controlled pilot scale field study. 200 kg of sodium persulphate was dissolved in 2000 L of water and injected into the subsurface. Electrical conductivity (EC), pH, sodium, persulphate, sulphate and BTEX concentrations were all monitored throughout the 158-day study period. Field research showed that there was a strong correlation between EC and sodium concentrations. Hence, this relationship allowed for real-time EC measurements to be used to effectively predict the extent of the injectate. Based on the calculated aqueous density of sodium persulphate at a concentration of 100g/L, predicted simulation model results and observed tracer field results, density effects were present and played a very important role in the transport of the injectate. The heterogeneous geology of the site also greatly influenced the transport of the injectate. The majority of the injectate appeared to have flowed out of the layers with higher hydraulic conductivity that intersected the upper and lower portion of the injection well’s screen length. The extent of the injected slug in the layers with lower hydraulic conductivity located in the centre portion of the injection well’s screen length was less in comparison. In general, areas with elevated tracer, persulphate and sulphate concentrations, also showed a decrease in BTEX concentration. Four main responses were observed. Group 1 consists of sampling points where tracer levels were elevated along with a corresponding short-term decrease in dissolved BTEX. Group 2 consists of sampling points where elevated tracer levels was observed along with a long-term apparent decrease in dissolved BTEX. Group 3 consists of sampling points where the tracer was elevated however dissolved BTEX levels remained essentially at background levels. And finally, group 4 consists of sampling points where the tracer was not observed to be elevated hence no decrease in dissolved BTEX was observed. Laboratory studies showed that the oxidation of BTEX compounds by unactivated sodium persulphate could be very successful. However, field study results showed that complexities such as heterogeneity of the field site and injectate density effects play a key role in the success of the remediation system.

There are some 15,000 known organophosphorus chemicals. Some of these OP’s, including VX and paraoxon, demonstrate an acute neurotoxicity due to the inhibition of cholinergic enzymes. Organophosphorus chemical warfare agents and pesticide neurotoxins are subject to hydrolysis by OP degrading enzymes. To be useful as a bioremediation or anti-chemical warfare agent, the enzyme must be tailored for, and integrated into, a practical application platform. Several studies have established enzyme-based countermeasures, describing such diverse applications as decontaminating foams for surface remediation, encapsulating enzyme with liposome for in vivo therapy, enzyme attachments to surfaces for biosensors and development of a corn expression system for large-scale enzyme production. The goal of the research described here is to select, investigate and improve the operational potential of organophosphate-degrading enzymes including Organophosphorus Hydrolase (OPH, 3.1.8.1) and Organophosphorus Acid Anhydrolase (OPAA, 3.1.8.2). Using saturation kinetics, the catalytic efficiencies of these two major detoxification enzymes were characterized with substrates representing each class of OP neurotoxin, phosphotriester, phosphothioate and phosphofluoridate. OPH presents superior kinetic parameters with each OP class tested. Variants of OPH were created to increase the operational effectiveness of OP hydrolytic enzymes against phosphorothioates. An H254S/H257L mutation in the active site resulted in an improvement in the kinetics (kcat/KM) for the phosphorothioate, demeton-S. To screen potential vascular protection therapies, an in vitro protocol was developed to predict enzymatic effectiveness for protection of acetylcholinesterase from acute OP-inhibition. The protection abilities of the enzymes were directly related to their second order rate constants as inhibitory levels of OP are below the KM of the enzymes. Consideration of contaminant nature concentration and enzyme kinetic parameters, kcat and KM, is critical to understanding decontamination and effective use of enzyme technology. These technologies continue to develop and provide promising new decontamination tools for OP compounds.

Immobilization and detoxification of chromium in the vadose zone is made possible by the existence of an effective reductant, SO2, that exists in a gaseous form at room temperature. Experimental studies were designed to characterize stoichiometry and kinetics of chromium reduction both in aqueous solutions at pH values near neutrality and in soil. First, batch experiments and elemental analyses were conducted to characterize the stoichiometry and kinetics of Cr(VI) reduction in water. The stoichiometric ratio of S(IV) removed to Cr(VI) removed ranged between 1.6 and 1.8. The overall reaction is believed to be the result of a linear combination of two reactions in which dithionate is an intermediate and sulfate is the stable oxidized product. The reaction was also rapid, with the half-time of about 45 minutes at pH 6 and about 16 hours at pH 7. A two-step kinetic model was developed to describe changes in concentrations of Cr(VI), S(IV), and S(V). Nonlinear regression was applied to obtain the kinetic parameters. The rate of reaction was assumed to be second-order with respect to [Cr(VI)] and first-order with respect to [S(IV)], and [S(V)]. The values for the rate coefficient for the first reaction (k1) were found to be 4.5 (?10%), 0.25 (?9.4%) (mM-2h-1) at pH 6 and 7, respectively. The values of the rate coefficient for the second reaction (k2) were 25 (?29%), 1.1 (? 30%) (mM-2h-1) at pH 6 and 7, respectively. The reaction rate decreased as pH increased. Experiments showed that the rate at pH 7 was lower than that at pH 6 by one order of magnitude. Second, batch experiments and elemental analyses were conducted to characterize the stoichiometry and kinetics of Cr(VI) reduction in soil. The stoichiometric ratio of S(IV) removed to Cr(VI) removed was almost 2, which is slightly higher than that for the reaction in water. This higher value may be due to S(IV) oxidation by soil-derived Fe(III). The reaction was rapid, with the half-time less than 2 minutes, which is faster than in water. The rate coefficients, k1 and k2, were 22 (?41%) and 13 (?77%) (M-2h-1), respectively.

We face a world in which a college degree increasingly dictates the likelihood of life success. At the same time, there has been an ever-increasing population of students who have not been prepared adequately through their high school education to meet the rigors of college/university-level content. This problem can be seen in the number of students needing Intermediate Algebra. Students who complete remedial courses with a grade of C or better are more likely to pass their first college-level mathematics course and continue their education until they have completed all coursework needed for a degree. Students entering colleges and universities underprepared for collegiate mathematics, reading, and writing have reached epidemic proportions, with 30% of the students needing remediation in one of these areas. A portion of this problem has been identified as mathematics anxiety. Because students have habituated mathematics failure, they are aware of their deficiencies, but still desire a college education. They bring with them years of negative emotions from repeated mathematics failures. These years of negative feelings about mathematics precipitated by repeated failures are often manifested as mathematics anxiety that must be addressed in order to improve students’ content knowledge. The purpose of this study is to investigate the effects of a web-based technology centric course, Assessment and Learning in Knowledge Spaces (ALEKS), on the remediation of college freshmen enrolled in an Intermediate Algebra class as compared to college freshmen enrolled in an Intermediate Algebra class taught using a traditional lecture method. Mathematics anxiety and attitude toward mathematics will also be investigated to determine if ALEKS can lower the anxiety associated with mathematics, as well as improve attitudes. An algebra test, mathematics anxiety rating scale, and mathematics attitude test was given to both groups of students at the beginning of the semester and at the end of the semester. The overall findings of this research suggested that ALEKS Intermediate Algebra students performed as well as the Control group taking a class in Intermediate Algebra taught by lecture. The anxiety of the Experimental group decreased more than the Control group, and the Experimental group’s attitude toward mathematics increased at a greater rate than did the Control group.

In situ capping is a remediation alternative for contaminated sediments which has been implemented to contain contaminants in sediments in rivers, lakes and ponds. One concern with in situ capping is that the additional load due to the in situ cap may cause consolidation-induced mobilization of non aqueous phase liquids (NAPL). Therefore, it is important to understand the consolidation behavior of NAPL contaminated soils. The difficulties of testing river-bed sediments are that these sediments usually are very soft, have very high porosities, and are very compressible. In addition, the contaminants in these sediments should be contained during testing. The primary objective of this research is to investigate the behavior of NAPL contaminated sediments under anisotropic consolidation. A modified triaxial testing system was developed to simulate the consolidation of very soft sediment specimens along with a reconstituted NAPL contaminated specimen preparation procedure. Kaolinite and Anacostia River sediments were used for the sediments’ solids phase. A low viscosity mineral oil, Soltrol 130, was used to represent the NAPL phase. Tap water was used as the water phase. PM199TM, a type of organophilic clay manufactured by CETCO, was used as well to study its effectiveness in containing expelled NAPL. Two sets of consolidation tests were performed: 1) tests on sediment specimens at various NAPL contents and porosities; and 2) tests on specimens contaminated with NAPL with organophilic clays either placed as a layer on top or mixed within the sediment. The results showed that NAPL mobilization was negligible below a threshold NAPL content. Hydraulic conductivities increased with increasing NAPL content up to four orders of magnitude. The tests with organophilic clay showed that when large enough amounts are used, NAPL expulsion can be completely stopped. Organophilic clay reached its full capacity independent of the NAPL content of the underlying sediment. / text

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy