Microcosms were constructed from aquifer sediment samples taken from an actively degrading chlorinated solvent contaminated site located in Virginia Beach, Virginia. The objective of this study was to determine if and how the addition of cyclodextrin (CD) affects reductive dechlorination of chlorinated ethenes. After chlorinated solvent degradation rates were established in anaerobic and aerobic microcosms, 100 mg/L of CD solution was added for a period of 21 days. CD was then removed after 26 days to simulate the degradation response of the aquifer in a post CD injection environment. Degradation rates were determined by analyzing PCE, TCE, and cis-DCE concentration data over the various phases of the experiment. Results from this study indicated that chlorinated solvent degradation could be either impaired or facilitated by the addition of CD. CD appeared to stimulate one anaerobic microcosm (IY-2c) where daughter production had not previously occurred. The activity of this microcosm was greatly enhanced by the addition of CD (0 uM/day to 13.89 uM/day). However, biotransformation of PCE in another anaerobic microcosm in which reductive dechlorination was occurring, ceased after the addition of CD (IY-1a). In a third group of microcosms the rate and extent of reductive dechlorination was greatly enhanced by the addition of CD. The effect of adding CD was also found to be highly dependent on the redox conditions in the microcosm, specifically if the conditions were strongly reducing. The most active microcosms, found in the Aerobic Group, also had the lowest ferrous iron concentrations (3.57 mg/L for BY-1a, 2.25 mg/L for BY-1b, and 0.41 mg/L for BY-1c). The microcosm (IY-2b) that showed no daughter production had the highest level of ferrous iron (44.22 mg/L). This study presents a qualitative approach to the affect of CD on MNA. / Master of Science

Laboratory microcosm experiments were conducted to assess the potential for biostimulation and bioaugmentation as source reduction measures in support of a monitored natural attenuation remedial strategy at Naval Amphibious Base (NAB) Little Creek. Previous work with laboratory microcosms conducted under simulated natural (unamended) conditions has demonstrated that indigenous dehalorespirators were capable of partial dechlorination of tetrachloroethene (PCE) to cis-dichloroethene (cis-DCE). This study attempts to achieve complete reductive dechlorination with amendments to static microcosms to test the hypotheses that nutrient-limited or microorganism-limited conditions exist in aquifer sediments obtained from the site. The enhanced bioremediation experiments were comprised of nutrient-amended microcosms receiving additions of electron donors, mineral medium, or anaerobic digester supernatant, and dechlorinating culture-amended microcosms were inoculated with a culture capable of transforming PCE to ethene. Reductive dechlorination in the nutrient-amended microcosms proceeded to cis-DCE over a 260-day study period, at slightly higher rates than in experiments conducted with aquifer sediments from the same location under natural conditions. Inoculation of aquifer sediments with a small amount of dechlorinating culture initiated rapid transformation of PCE to vinyl chloride (VC) by day 18 of the study. Zero-order rates of PCE dechlorination in unamended, propionate-, formate-, mineral medium-, digester supernatant-, and dechlorinating culture-amended microcosms were 0.24, 0.750, 1.30, 0.339, 0.177, and 1.75 µM/day, respectively. The results of this study suggest that an engineered biostimulation approach alone may not be as beneficial for PCE source reduction at NAB Little Creek, than bioaugmentation with competent dehalorespirators, along with the inclusion of supplemental nutrients which would be available to stimulate dechlorination activity of both indigenous and introduced microorganisms. / Master of Science

Monitored natural attenuation (MNA) has been widely used as a remedial strategy, acknowledged by the EPA as the most appropriate technology for cost effective remediation under certain site conditions. Despite the widespread use of MNA, empirical methods are lacking to evaluate the sustainability of MNA at a site. The objective of this thesis is to investigate the natural attenuation capacity (NAC) as a quantitative metric for evaluating the sustainability of MNA for contaminants in groundwater systems. Five DoD sites were selected for this study, where the common thread between the sites is the existence of a mature chlorinated ethene groundwater plume and the use of MNA as the long-term remediation strategy. Constituent specific NAC values were quantified and statistically examined to determine past performance of MNA at the sites. A conceptual decision model was developed to be a framework of the statistical tools demonstrated in this thesis. Analyzing MNA sustainability at a site can be separated into two components; past performance of natural attenuation and evaluation of current MNA parameters. The former is the focus of this thesis where NAC is the screening metric and the temporal trend in the rate of natural attenuation being evaluated. Within the conceptual decision model, the use of NAC as a screening tool in combination with a specific analysis of MNA parameters allows engineers, regulators, and decision makers to clearly determine whether MNA at a site is sustainable and whether site specific remediation goals will be met. / Master of Science

<p>Chlorinated solvent are volatile organic substances that can be harmful for humans and for the environment. Examples of common chlorinated solvents are perchloroethene, PCE, and trichloroethene, TCE. Chlorinated solvents appear as contaminants in soils primarily where they have been used as washing fluids in dry-cleaning facilities or as degreasers in metal industries. Chlorinated solvents are DNAPLs (dense non-aqueous phase liquids), which means that they are not easily dissolved in water and that they sink to the bottom of the aquifer. Adsorption to soils is low so chlorinated solvents are mobile in soils. Chlorinated solvents can be harmful at low concentrations. Complete degradation can only occur under specific conditions. Because of the properties of these substances, investigation and analysis methodology are extra important for determining transport and risks in a contaminated area.</p><p>In this work, investigation and analysis methods for chlorinated solvents are described. Planning, fieldwork, modeling and risk analysis are described.</p><p>Projects concerning chlorinated solvents completed by Golder Associates AB have been compiled and analysed. Based on the compilation, conclusions have been drawn and statistics have been calculated. Investigations of the relation between concentrations in different media have been made as well as investigations of the relation between degradation products at different distances from the source and at different times after release. The data from the environmental investigations have been compared with theoretical literature values and modelling results.</p><p>The results show that there is a large natural variation in the data and that the differences between different areas are quite large. The results confirm the theory that the percentage of degradation products increases with distance from the source and with time from release. In addition, solvents with a higher degree of chlorination seams to appear to a greater extent in the soil and the more volatile substances seams to appear to a greater extent in the soil air.</p> / <p>Klorerade lösningsmedel är flyktiga klorerade organiska ämnen som kan vara skadliga för människor och miljön. Exempel på vanliga klorerade lösningsmedel är perkloreten, PCE och trikloreten, TCE. Klorerade lösningsmedel förekommer som markföroreningar främst efter användning som tvättvätska i kemtvättar och som avfettningsmedel i metallindustrin. Klorerade lösningsmedel är DNAPLs (dense non-aqueous phase liquids), det innebär att de är svårlösliga i vatten och att de sjunker och lägger sig på botten av akviferen. Fastläggningen i jorden är liten hos klorerade lösningsmedel som därmed är rörliga i marken. De är farliga redan vid små koncentrationer och fullständig nedbrytning sker endast under vissa förutsättningar. Ämnenas egenskaper gör att undersöknings- och analysmetodiken är viktig för att riktigt kunna bestämma deras utbredning och risk på ett förorenat område.</p><p>I detta arbete beskrivs undersöknings- och analysmetodiken för områden förorenade med klorerade lösningsmedel. Upplägg, fältarbete, modellering och riskbedömning beskrivs.</p><p>Projekt som handlar om klorerade lösningsmedel utförda av Golder Associates AB har sammanställts. Sammanställningen har analyserats och utifrån den har olika slutsatser dragits och statistik beräknats. Bland annat har samband mellan halter i olika medier samt samband mellan halter av nedbrytningsprodukter på olika avstånd från källan respektive efter olika lång tid från läckage har undersökts. Data från miljöundersökningarna har även jämförts med teoretiska litteraturvärden samt modelleringsresultat.</p><p>Resultatet visar att den naturliga spridningen av data är stor samt att resultaten skiljer sig åt mellan olika områden. Resultaten bekräftar teorierna att halten nedbrytningsprodukter ökar med avståndet från källan och med tiden samt att ämnen med högre kloreringsgrad finns i större utsträckning i jorden och att flyktigare ämnen finns i större utsträckning i porluften.</p>

Chlorinated solvent are volatile organic substances that can be harmful for humans and for the environment. Examples of common chlorinated solvents are perchloroethene, PCE, and trichloroethene, TCE. Chlorinated solvents appear as contaminants in soils primarily where they have been used as washing fluids in dry-cleaning facilities or as degreasers in metal industries. Chlorinated solvents are DNAPLs (dense non-aqueous phase liquids), which means that they are not easily dissolved in water and that they sink to the bottom of the aquifer. Adsorption to soils is low so chlorinated solvents are mobile in soils. Chlorinated solvents can be harmful at low concentrations. Complete degradation can only occur under specific conditions. Because of the properties of these substances, investigation and analysis methodology are extra important for determining transport and risks in a contaminated area. In this work, investigation and analysis methods for chlorinated solvents are described. Planning, fieldwork, modeling and risk analysis are described. Projects concerning chlorinated solvents completed by Golder Associates AB have been compiled and analysed. Based on the compilation, conclusions have been drawn and statistics have been calculated. Investigations of the relation between concentrations in different media have been made as well as investigations of the relation between degradation products at different distances from the source and at different times after release. The data from the environmental investigations have been compared with theoretical literature values and modelling results. The results show that there is a large natural variation in the data and that the differences between different areas are quite large. The results confirm the theory that the percentage of degradation products increases with distance from the source and with time from release. In addition, solvents with a higher degree of chlorination seams to appear to a greater extent in the soil and the more volatile substances seams to appear to a greater extent in the soil air. / Klorerade lösningsmedel är flyktiga klorerade organiska ämnen som kan vara skadliga för människor och miljön. Exempel på vanliga klorerade lösningsmedel är perkloreten, PCE och trikloreten, TCE. Klorerade lösningsmedel förekommer som markföroreningar främst efter användning som tvättvätska i kemtvättar och som avfettningsmedel i metallindustrin. Klorerade lösningsmedel är DNAPLs (dense non-aqueous phase liquids), det innebär att de är svårlösliga i vatten och att de sjunker och lägger sig på botten av akviferen. Fastläggningen i jorden är liten hos klorerade lösningsmedel som därmed är rörliga i marken. De är farliga redan vid små koncentrationer och fullständig nedbrytning sker endast under vissa förutsättningar. Ämnenas egenskaper gör att undersöknings- och analysmetodiken är viktig för att riktigt kunna bestämma deras utbredning och risk på ett förorenat område. I detta arbete beskrivs undersöknings- och analysmetodiken för områden förorenade med klorerade lösningsmedel. Upplägg, fältarbete, modellering och riskbedömning beskrivs. Projekt som handlar om klorerade lösningsmedel utförda av Golder Associates AB har sammanställts. Sammanställningen har analyserats och utifrån den har olika slutsatser dragits och statistik beräknats. Bland annat har samband mellan halter i olika medier samt samband mellan halter av nedbrytningsprodukter på olika avstånd från källan respektive efter olika lång tid från läckage har undersökts. Data från miljöundersökningarna har även jämförts med teoretiska litteraturvärden samt modelleringsresultat. Resultatet visar att den naturliga spridningen av data är stor samt att resultaten skiljer sig åt mellan olika områden. Resultaten bekräftar teorierna att halten nedbrytningsprodukter ökar med avståndet från källan och med tiden samt att ämnen med högre kloreringsgrad finns i större utsträckning i jorden och att flyktigare ämnen finns i större utsträckning i porluften.

Naturally occurring bacterial populations are capable of detoxifying chlorinated compounds and immobilizing the radionuclide uranium via reductive processes. This study addressed the following three knowledge gaps in the fields of chlorinated solvent and uranium bioremediation, 1) the risks and benefits of coupling bioremediation with thermal treatment for clean-up of chlorinated ethene-contaminated sites, 2) the accuracy of available techniques for the monitoring of chlorinated solvent bioremediation, and 3) the role of gram positive Desulfitobacterium spp. in uranium immobilization. Experiments demonstrated that thermal treatment increases electron donor availability, but the increased electron donor was not used to fuel reductive dechlorination and was actually consumed for methanogenesis. Two approaches for monitoring chlorinated solvent bioremediation were investigated, molecular techniques and compound-specific isotope analysis (CSIA). Results demonstrated that while Dehalococcoides (Dhc) gene expression was up-regulated under conditions inhibitory to dechlorination, the isotope effects associated with dechlorination reactions catalayzed by Dhc populations in consortia and in pure cultures were similar. U(VI) reduction by multiple Desulfitobacterium isolates was demonstrated. Interestingly, while almost all U(VI)-reducing populations have been reported to produce uraninite (UO2), the product of U(VI) reduction by Desulfitobacterium isolates was a unique form of insoluble mononuclear U(IV).

Monitored natural attenuation has been particularly used at sites where petroleum hydrocarbons and chlorinated solvents have contaminated soil and groundwater. One of the important aspects of the methodology that has been recognized recently is that the mass removal rates, the most important parameter to determine effectiveness of the methodology, is controlled by the groundwater flow regime and the aquifer heterogeneity. Considering this recognition, the primary objective of this study is to quantitatively describe the relationship between the natural attenuation rates and aquifer heterogeneity using numerical simulation techniques. To represent different levels of aquifer heterogeneity, the hydraulic conductivity distribution (ln K) is statistically simulated with the numerical algorithm, Turning Bands Random Field Generator, by changing the statistical parameters, Coefficient of Variation (CV) and correlation length (h) and Visual MODFLOW and RT3D software programs are used for the simulation of groundwater flow and chlorinated solvent transport. Simulation results showed that degradation rates and the shape of the contaminant plumes show variations for different heterogeneity levels. Increasing CV resulted in the decrease in the transport of the plume and shrinkage in the areal extend. On the other hand, &ldquo / h&rdquo / determined the shape and the size of the plume through its affect on mechanical dispersion. For a given &ldquo / h&rdquo / , degradation rates increased with increasing CV, but change in &ldquo / h&rdquo / did not show a regular trend. Such findings are expected to be beneficial when assessing the effectiveness of natural attenuation process for a selected site during the feasibility studies without need for detailed site characterization.

Chlorinated solvents are common contaminants in soil and water. Under anaerobic conditions microbes are capable of transforming chlorinated solvents into ethylene which would result in a remediation of the contaminated area. In order to use natural attenuation as a remediation method evidence of continuous degradation is required. Furthermore, the degradation must occur at a sufficient rate and continuous monitoring of the site is needed until the demanded levels are achieved. A field study was performed on the basis of data from a dry-cleaning facility contaminated mainly by perchloroethylene. The purpose of the study was to define the existing situation regarding distribution and transformation of contaminant in order to evaluate the possibilities of using natural attenuation as a method of remediation. Degradation of perchloroethylene proceeds through successive removal of chlorine, with the formation of trichloroethylene, dichloroethylene, vinyl chloride and ethylene. There exists evidence of degradation as far as vinyl chloride on the site but whether transformation continues to ethylene is not established. The computer model Biochlor was used to simulate distribution and degradation of the contaminants. The site possesses a complex hydrogeology and the existing data are not sufficient to distinguish the effect of degradation from other factors such as spreading of contaminant between different layers of soil. Since degradation failed to be quantified, natural attenuation can not be recommended as a safe remediation method at the considered site without further investigations. / Klorerade lösningsmedel är vanligt förekommande föroreningar i mark och vatten. Under anaeroba förhållanden kan mikrober omvandla klorerade kolväten till eten vilket leder till rening av det förorenade området. För att kunna använda denna naturliga nedbrytning som saneringsmetod krävs bevis för att nedbrytning fortskrider i tillräcklig utsträckning för att rena området och därefter krävs kontinuerlig provtagning till dess målen för saneringen har uppnåtts. En fallstudie utfördes utifrån data från en kemtvättsfastighet förorenad av i första hand perkloreten. Syftet var att kartlägga föroreningssituationen med avseende på spridning och nedbrytning av de klorerade föreningarna för att undersöka om naturlig nedbrytning var en möjlig framtida saneringsmetod. Nedbrytning av perkloreten sker stegvis genom att klor avspjälkas, under bildande av produkterna trikloreten, dikloreten, vinylklorid och etengas. Nedbrytning av förorening har konstaterats ske på fastigheten fram till vinylklorid men huruvida nedbrytning avstannat där eller fullföljts till etengas är ej klarlagt. Datormodellen Biochlor användes för att simulera spridning och nedbrytning av utsläppet. Fältplatsen har en komplex hydrogeologi och befintliga fältdata var inte tillräckliga för att särskilja nedbrytningens effekt från faktorer såsom spridning av förorening mellan olika jordlager. Eftersom nedbrytningen inte kunde kvantifieras kan naturlig nedbrytning inte rekommenderas som säker saneringsmetod på denna fältplats utan kompletterande analyser.

Chlorinated ethenes are considered one of the most prevalent sources of groundwater contamination in developed countries. Natural attenuation of chlorinated ethenes is possible through the process of microbial reductive dechlorination. Reductive dechlorination can occur in contaminated aquifers where there are sufficient amounts of organic carbon and reducing redox conditions to support dechlorinating microorganisms. Natural organic carbon (NOC) from dissolved aquifer sediment is thought to be the source of fermentable compounds needed to produce molecular hydrogen that functions as the primary electron donor for reductive dechlorination. Therefore, in an anaerobic aquifer, the production of molecular hydrogen from the fermentation of NOC drives the reductive dechlorination process. The variability and distribution of potential bioavailable organic carbon (PBOC) at a site is relatively unknown and any potential relationships between PBOC and the physical properties of the aquifer sediment have not been evaluated. Exploring relationships between the grain size of aquifer sediment PBOC may help to determine the feasibility of natural attenuation as a long-term remediation strategy at chlorinated ethene-contaminated sites. Because hydraulic conductivity is directly related to aquifer sediment grain size, zones of high hydraulic conductivity may promote greater microbial activity or biodegradation because of the increased availability of PBOC and nutrient flux. To determine potential relationships between PBOC and aquifer sediment grain size, two experiments were performed. PBOC was measured for 106 sediment samples impacted by chlorinated solvent contamination from an anaerobic type II site through a multiple liquid extraction process (Rectanus et al. 2007). Grain size distributions for each of the 106 sediment samples were determined by conducting sieve analyses. The results of both experiments were compared to explore relationships between PBOC and sediment grain size and to evaluate spatial distribution of both in the surficial aquifer. / Master of Science

The feasibility of applying a recently developed liquid-liquid extraction method termed Predispersed Solvent Extraction (PDSE) in an <i>ex situ</i> pump-and-treat system to remove trace amounts of dissolved chlorinated solvents like perchloroethylene (PCE) and trichloroethylene (TCE) from contaminated ground water has been investigated. In PDSE, the solvent is comminuted into globules with diameters ranging from submicron to 100 microns, and stabilized by a surfactant film prior to contact with the aqueous feed. These stabilized globules, termed oil-core aphrons (OCAs), disperse readily in water since water is the continuous phase in systems where the oil-water phase ratios can be as high as 9. Due to their fine particle size and large surface area, high extraction mass-transfer rates are achieved with minimal mixing. OCA phase separation from water can be expedited with microbubble foam flotation. Experiments in this investigation focused on PDSE process development for this groundwater remediation application. Distribution coefficients for PCE and TCE in possible OCA solvents were determined experimentally and agree with published calculated values. Various surfactant/solvent OCA formulations using the aforementioned solvents were examined with emphasis on creating a weakly stable dispersion which would maximize extraction efficiency yet destabilize sufficiently to permit rapid flotation with minimum losses in the raffinate. Accelerating phase separation, hence solvent recovery, through dispersion chemical destabilization with salts, coagulants, and flocculants at varied pH was examined with and without microbubble flotation. The presence of OCAs in the aqueous phase reduced vapor phase concentrations of PCE as much as 96% and was assessed through apparent Henry's Law constants. TCE concentrated in dodecane OCA extract was degraded with a CO-dehydrogenase enzyme complex to cis 1,2-dichloroethylene, trans 1,2-dichloroethylene, and 1,1-dichloroethylene, and vinyl chloride as a possible means of destroying TCE dissolved in the extract. Based on the implications of these experiments, the development of a PDSE <i>ex situ</i> pump-and-treat system appears technically feasible and a conceptual process layout has been provided. / Master of Science