published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

O método de injeção de ar é utilizado para a descontaminação de solos e lençóis freáticos contaminados com Compostos Orgânicos Voláteis (VOCs). O ar injetado no solo na zona saturada, ao subir para a zona não saturada, volatiliza os contaminantes. A eficiência da remediação por esse método está diretamente ligada à região de solo em que ocorre o fluxo de ar. Essa região é denominada de zona de influência e é afetada por vários fatores tais como: tipo e estrutura do solo, permeabilidade e pressão de injeção. No presente trabalho foram realizados estudos de fluxo de ar em solos saturados em um modelo físico bidimensional com o objetivo de avaliar a zona de influência formada. Os ensaios bidimensionais têm por finalidade a visualização dessa zona de influência; para isso foi utilizado um tanque transparente feito de placas de acrílico. Para a realização dos ensaios foram utilizados três tipos distintos de solo, uma areia natural denominada de Areia Osasco, uma areia comercial e uniforme (Areia do IPT) e um solo residual utilizado para criar as lentes de baixa permeabilidade. Também foram realizados ensaios de laboratório para a caracterização dos solos em estudo, tais como: curva de retenção, índice de vazios máximo e mínimo, granulometria, permeabilidade a água e ao ar. Os ensaios realizados no modelo (tanque) mostraram, como visto na literatura, que a granulometria e a estrutura do solo são as principais responsáveis pela formação de caminhos preferenciais de ar no solo. A zona de influência formada durante a injeção de ar nos ensaios com a Areia Osasco não foi simétrica devido à heterogeneidade do solo, já a formada nos ensaios com a Areia do IPT foi simétrica por causa da uniformidade do solo. A Areia do IPT apresentou uma zona de influência mais estreita do que a da Areia Osasco, isso ocorreu em função da menor porosidade da Areia Osasco, pois quanto menor a porosidade maior a tortuosidade e maior a expansão lateral. Os ensaios com as lentes de baixa permeabilidade mostraram que pequenas variações na configuração do solo podem influenciar a eficiência do método já que a região logo acima das lentes não foi atingida pelo ar. O aumento da pressão de injeção durante os ensaios fez com que mais canais de ar fossem formados causando um aumento do tamanho da zona de influência. / The method of air sparging is used for remediation of soil and groundwater contaminated with Volatile Organic Compounds (VOCs). In this process the air is injected into the soil in the saturated zone to ascend to the vadose zone and volatilizes the contaminants. The efficiency of air flow remediation is directly linked with the region of soil in which the flow occurs. This region is called as zone of influence and is affected by several factors such as: type and structure of the soil, permeability and pressure of injection. In the present work the air flow in saturated soils was investigated using a bidimensional physical model to evaluate the zone of influence formed. The objective of the tests was to obtain informations about zone of influence. A transparent tank made by acrylic plates was used. For these tests it was used three different types of soil: natural sand, called Osasco sand, a commercial and uniform sand called IPT sand and a residual soil used to create the lenses with low permeability. Laboratory tests such as water retention, minimum and maximum voids ratio, water and air permeability were performed to characterize the soils used in this study. Tests performed in the model (tank) showed, like those in the literature, that the particle size and soil structure are mainly responsible to create the preferential paths of air in soil. The zone of influence formed during the injection of air in the tests with Osasco sand was not symmetrical due to the heterogeneity of the soil; on the other hand the test performed with IPT sand was symmetrical due to its uniformity. The IPT sand showed a narrower zone of influence than Osasco sand, this was due to the lower porosity of the Osasco sand. Lower porosity imply in higher tortuosity and greater lateral expansion. Testes performed with low permeability lenses within the sand showed that small variations in the structure of the soil can affect the efficiency of the method because the region immediately above the lens is not reached by the air. The increase in the pressure of injection during the experiments induced the formation of more air channels causing an increase in the size of the zone of influence.

O método de injeção de ar é utilizado para a descontaminação de solos e lençóis freáticos contaminados com Compostos Orgânicos Voláteis (VOCs). O ar injetado no solo na zona saturada, ao subir para a zona não saturada, volatiliza os contaminantes. A eficiência da remediação por esse método está diretamente ligada à região de solo em que ocorre o fluxo de ar. Essa região é denominada de zona de influência e é afetada por vários fatores tais como: tipo e estrutura do solo, permeabilidade e pressão de injeção. No presente trabalho foram realizados estudos de fluxo de ar em solos saturados em um modelo físico bidimensional com o objetivo de avaliar a zona de influência formada. Os ensaios bidimensionais têm por finalidade a visualização dessa zona de influência; para isso foi utilizado um tanque transparente feito de placas de acrílico. Para a realização dos ensaios foram utilizados três tipos distintos de solo, uma areia natural denominada de Areia Osasco, uma areia comercial e uniforme (Areia do IPT) e um solo residual utilizado para criar as lentes de baixa permeabilidade. Também foram realizados ensaios de laboratório para a caracterização dos solos em estudo, tais como: curva de retenção, índice de vazios máximo e mínimo, granulometria, permeabilidade a água e ao ar. Os ensaios realizados no modelo (tanque) mostraram, como visto na literatura, que a granulometria e a estrutura do solo são as principais responsáveis pela formação de caminhos preferenciais de ar no solo. A zona de influência formada durante a injeção de ar nos ensaios com a Areia Osasco não foi simétrica devido à heterogeneidade do solo, já a formada nos ensaios com a Areia do IPT foi simétrica por causa da uniformidade do solo. A Areia do IPT apresentou uma zona de influência mais estreita do que a da Areia Osasco, isso ocorreu em função da menor porosidade da Areia Osasco, pois quanto menor a porosidade maior a tortuosidade e maior a expansão lateral. Os ensaios com as lentes de baixa permeabilidade mostraram que pequenas variações na configuração do solo podem influenciar a eficiência do método já que a região logo acima das lentes não foi atingida pelo ar. O aumento da pressão de injeção durante os ensaios fez com que mais canais de ar fossem formados causando um aumento do tamanho da zona de influência. / The method of air sparging is used for remediation of soil and groundwater contaminated with Volatile Organic Compounds (VOCs). In this process the air is injected into the soil in the saturated zone to ascend to the vadose zone and volatilizes the contaminants. The efficiency of air flow remediation is directly linked with the region of soil in which the flow occurs. This region is called as zone of influence and is affected by several factors such as: type and structure of the soil, permeability and pressure of injection. In the present work the air flow in saturated soils was investigated using a bidimensional physical model to evaluate the zone of influence formed. The objective of the tests was to obtain informations about zone of influence. A transparent tank made by acrylic plates was used. For these tests it was used three different types of soil: natural sand, called Osasco sand, a commercial and uniform sand called IPT sand and a residual soil used to create the lenses with low permeability. Laboratory tests such as water retention, minimum and maximum voids ratio, water and air permeability were performed to characterize the soils used in this study. Tests performed in the model (tank) showed, like those in the literature, that the particle size and soil structure are mainly responsible to create the preferential paths of air in soil. The zone of influence formed during the injection of air in the tests with Osasco sand was not symmetrical due to the heterogeneity of the soil; on the other hand the test performed with IPT sand was symmetrical due to its uniformity. The IPT sand showed a narrower zone of influence than Osasco sand, this was due to the lower porosity of the Osasco sand. Lower porosity imply in higher tortuosity and greater lateral expansion. Testes performed with low permeability lenses within the sand showed that small variations in the structure of the soil can affect the efficiency of the method because the region immediately above the lens is not reached by the air. The increase in the pressure of injection during the experiments induced the formation of more air channels causing an increase in the size of the zone of influence.

De nos jours, la préservation de l’environnement est un enjeu majeur. Avant cette prise de conscience, de nombreux polluants ont été rejetés dans la nature. Parmi eux, les hydrocarbures sont très souvent rencontrés. Or, ils sont reconnus pour leur toxicité et leur persistance accrue. La mise en place de méthodes efficaces de dépollution est donc primordiale. Les méthodes classiques nécessitent l’excavation ou le pompage des zones contaminées, imposant un coût de dépollution élevé. C’est pourquoi des techniques de dépollution in-situ ont été développées afin de réduire ces coûts, tout en garantissant des rendements de dépollution efficaces. Les travaux menés durant cette Thèse ont permis de déterminer, pour plusieurs techniques de traitement, les facteurs limitants inhérents à la technique, mais aussi de quantifier le rôle du contact entre agents de traitement et zone polluée ou des effets densitaires. Les techniques in-situ utilisées sont : l’oxydation chimique in situ, le lavage par tensio-actifs, l’injection d’air (sparging) et le traitement thermique. Trois niveaux d’expérience ont été étudiés : le batch, la colonne et le pilote 3D. Les réacteurs fermés, ont permis la comparaison des oxydants en statiques face à une matrice plus ou moins riche en matières organiques. Les colonnes ont mis en avant l’influence du mode d'injection appliqué vis-à-vis des propriétés physico-chimiques des polluants (cinétique réactionnelle, pression de vapeur, température d’ébullition, etc.). Les pilotes 3D, d’un volume d’un 1 m3, ont permis de comparer les différentes techniques sur un milieu hétérogène présentant des zones peu perméables, difficiles à traiter. A partir des résultats acquis et de modélisation numérique des expériences, il est dorénavant possible de mieux ajuster la méthode de traitement et surtout de comparer différentes méthodes pour un contexte hydrogéologique donné. / Pollution of soils and aquifers by Diesel fuel compounds is a widespread remediation issue. Problems due to soil remediation are more and more difficult to treat. Hydrocarbons are often encountered. But they are known for their toxicity and increased persistence. The establishment of effective remediation methods is paramount. Conventional methods require excavation or pumping contaminated areas requiring a high abatement costs. That is why, in-situ remediation techniques have been developed to reduce these costs while ensuring efficient pollution control returns. The work done during this thesis has determined for several treatments, the limiting factors inherent the treatment, but also quantifies the role of contact between agents and pollutants or density effects. In-situ treatments are: in situ chemical oxidation, surfactants flushing, air sparging and thermic treatment. Three levels of experience were investigated: batch, column and 3D Pilot. Batchs, enabled the comparison of oxidants in sand and natural soil. The columns have highlighted the influence of the injection method applied occurs toward the physical and chemical properties of contaminants (reaction kinetics, vapor pressure, boiling temperature, etc.). 3D Pilot, have a volume of 1m3. They were used to compare the different treatments on a heterogeneous medium having low permeability zones, difficult to treat. From the results of numerical modeling and experiences, it is possible to adjust the treatment method and especially to compare different methods for a given hydrogeological context.

Prior to the passage of the 1976 Resource Conservation and Recovery Act (RCRA) 1.6 million bare steel Underground Storage Tanks (UST) were in use in the United States. Many of them were leaking. In Indiana approximately 13,000 UST remain but have been upgraded to meet current industry and regulatory standards. Cleaning up the petroleum releases from leaking UST has continued since it became evident that bare steel underground tanks leaked. In Northwest Indiana glacial moraine and outwash deposits from the Wisconsin Ice Age that retreated 10,000 years ago left 200 feet of glacial till above the underlying bedrock. Soil Vapor Extraction (SVE) and Air Sparging (AS) have proven to be effective and provide significant cost savings for remediation in the glacial deposits in Northwest Indiana. Indiana also has the Excess Liability Trust Fund (ELTF) to help pay for and to expedite clean-up of releases from registered UST. Cleaning up petroleum releases requires the appropriate technology for the localized geology, adequate funding, and appropriate guidance from state and federal regulations. This study discusses these issues at three sites in Northwest Indiana to demonstrate how technology, funding, and regulatory compliance must collaborate to work in the field.