The effect of calcium uptake by hydration and diffusion from an adjacent calcium-rich soil on the performance of a geosynthetic clay liner (GCL) is examined for three cases. In Case 1 the GCL rested directly on a soil with a high calcium (1800 mg/l) concentration in the pore water (called “calcium rich soil” herein). Case 2 involved a GCL resting on 300 mm of soil with a low (200 - 300 mg/l) calcium concentration in the pore water (“foundation soil”) overlying the calcium rich soil. In the third (“control case”), the GCL only rested on the foundation soil. The overburden pressure was 15 kPa. The moisture content of GCL increased to 96%, 86% and 108% in the first 279 days for Cases 1, 2 and 3 respectively. Under isothermal conditions, the GCL moisture content decreased to 80% and 67% for Cases 1 and 2 respectively and increased to 113% for Case 3. After 1100 days, the hydraulic conductivity (k) of the GCL was 4×10-11 m/s for Case 3 but had increased up to about 7×10-11 m/s and 2×10-10 m/s for cases with and without the foundation layer respectively. The results are used to calibrate finite element models. A good correlation was found between k the bulk void ratio (eB) of GCL. Leakage and contaminant transport through 10 mm diameter hole in a geomembrane in a composite liner involving a GCL is examined at a stress of 100 kPa for hydraulic heads of 0.3 or 1 m. When permeated with distilled water, the interface transmissivity (θ) was about 2.3 × 10 11 m2/s. After 800 days of permeation with 0.14M NaCl there was only about 3% increase in the flow despite an order of magnitude increase in GCL permeability near the hole because θ decreased from 2.3×10-11 m2/s to 1.1×10-11 m2/s and controlled the leakage despite the increase in GCL permeability. Numerical modeling demonstrated reasonable agreement with the observed transport. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2010-09-09 12:20:42.298

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Nesta pesquisa, uma CÃlula Experimental (CE) de ResÃduos SÃlidos Urbanos (RSU) foi instalada numa Ãrea nÃo utilizada do Aterro SanitÃrio Metropolitano Oeste de Caucaia (ASMOC), RegiÃo Metropolitana de Fortaleza, com o objetivo de se estudar o comportamento de gramÃneas na sua superfÃcie, visando a reduÃÃo das emissÃes de CH4 e CO2 para a atmosfera e a produÃÃo de biomassa vegetal. As estimativas das emissÃes de gases foram realizadas por meio de ensaios com placa de fluxo estÃtico na cobertura convencional (branco) e nas coberturas cultivadas, alÃm das mediÃÃes feitas no dreno; todos em duas campanhas. Os cultivos de capim MombaÃa, Massai, Andropogon, Buffel e da grama Bermuda foram avaliados com relaÃÃo as caracterÃsticas morfogÃnicas, estruturais, produtivas e nutricionais. A Ãrea que recebeu a CE foi previamente estudada por meio do reconhecimento do perfil estratigrÃfico do subsolo e do nÃvel d‟Ãgua, caracterizaÃÃo dos solos em termos geofÃsicos (granulometria, limites de consistÃncia, compactaÃÃo Proctor Normal, permeabilidade à Ãgua) e quanto à fertilidade. Os RSU foram estudados quanto à composiÃÃo gravimÃtrica, densidade aparente, teor de umidade e seu lixiviado analisado do ponto de vista fÃsico-quÃmico. Os gases emitidos pelo dreno, na primeira campanha (1ÂC) foram compostos, em mÃdia, por 14,7% de CO2, 8,0% de CH4, 11,4% de O2 e 65,9% de outros gases. Na segunda campanha (2ÂC) houve um aumento na concentraÃÃo (%) dos dois principais gases de interesse (CO2: 0,3 vezes e CH4: 0,5 vezes) e reduÃÃo na concentraÃÃo dos demais (O2: 0,2 vezes e OG: 0,1 vezes): 19,0% de CO2, 11,8% de CH4, 8,7% de O2 e 60,4% de outros gases. Os gases emitidos pela cobertura (branco) foram (em %) menores que os emitidos pelo dreno, mostrando retenÃÃo: 1ÂC = 11,6% de CO2, 6,5% de CH4, 9,1% de O2 e 72,7% de outros gases; 2ÂC = 14,9% de CO2, 9,4% de CH4, 7,2% de O2 e 68,5% de outros gases. Em relaÃÃo aos fluxos mÃssicos houve aumento entre as campanhas (mÃdia): 2,5 x 10-3 e 3,6 x 10-3 g/m2.s de CH4 (1ÂC e 2ÂC, respectivamente), 1,2 x 10-2 e 1,5 x 10-2 g/m2.s de CO2 (1ÂC e 2ÂC). Os fluxos volumÃtricos foram (mÃdia): 4,0 x 10-6 e 5,7 x 10-6 m3/m2.s de CH4 (1ÂC e 2ÂC) e 7,0 x 10-6 e 8,8 x 10-6 m3/m2.s de CO2 (1ÂC e 2ÂC). Cabe observar que os fluxos estiveram dentro dos intervalos da literatura. Em relaÃÃo aos cultivos, observou-se que mesmo colocadas sobre solo tÃpico de aterro sanitÃrio e sem tratamento especial na cobertura ou no cultivo, as sementes dos quatro capins estudados e da grama Bermuda apresentaram germinaÃÃo dentro dos prazos biolÃgicos previstos. Assim, houve sobrevivÃncia dessas espÃcies sobre o solo do aterro sanitÃrio, porÃm com indicadores de desenvolvimento vegetal menores em relaÃÃo a literatura, contribuindo para isso o efeito negativo da extrema compactaÃÃo da cobertura e o baixo grau de fertilidade do solo. Cada cultivo teve uma capacidade diferente de impedir as emissÃes dos gases pela cobertura. Em ordem decrescente, observou-se (mÃdia): MombaÃa (2,6 e 3,8% de CH4 na 1ÂC/2ÂC; 4,6 e 6,0% de CO2 na 1ÂC/2ÂC), Massai (2,0 e 2,8% de CH4; 3,5 e 4,5% de CO2), Andropogon (1,1 e 1,5% de CH4; 1,9 e 2,5% de CO2), Bermuda (0,9 e 1,3% de CH4; 1,6 e 2,0% de CO2) e capim Buffel (0,4 e 0,6% de CH4; 0,5 e 0,6% de CO2). Os fluxos mÃssicos e volumÃtricos tambÃm foram menores no solo cultivado com capim MombaÃa e maiores no capim Buffel e isso manteve relaÃÃo com as principais caracterÃsticas morfogÃnicas, estruturais, produtivas e nutricionais utilizadas na avaliaÃÃo da sobrevivÃncia e desenvolvimento dos cultivos. / An Urban Solid Waste (USW) Experimental Cell (EC) was set up in an unused area of the West Metropolitan Landfill in Caucaia (ASMOC), in the Metropolitan Region of Fortaleza, with the aim of studying the behavior of different grasses planted on its cover layer in order to reduce atmospheric emissions of CO2 and CH4 and for the production of plant biomass. Gas emissions were tested with static flow plates on the normal cover layer (blank) and on the planted areas, in addition to the measurements taken on the landfill drainage. All measurements were made in two different campaigns. The morphogenesis, structural, productive and nutritional features of the Mombasa, Massai, Andropogon, Buffel and Bermuda grasses were evaluated. The area on which the EC was located was studied prior to the seeding, including a survey of the subsoil stratigraphic profile and groundwater levels, a geophysical soil characterization (grain size, Atterberg limits, normal Proctor compaction, water permeability) and fertility. The USW was studied for its gravimetric composition, density and moisture content and its leachate was analyzed from a physical and chemical perspective. The gases emitted by the drainage in the first campaign (C1) were composed on average by 14.7% CO2, 8.0% CH4, 11.4% O2, and 65.9% of other gases. In the second campaign (C2) there was an increase in the concentration (%) of the two main gases of interest (CO2: 0.3 times; CH4: 0.5 times) and a reduction in the concentration of the others (O2: 0.2 times, and other gases 0.1 times), with the following concentrations: CO2 19.0%, CH4 11.8%, O2 8.7%, and 60.4% of other gases. The gas emissions of the normal cover layer (blank) were lower than those of the drainage, showing a certain retention: C1: CO2 11.6%, CH4 6.5%, O2 9.1% and 72.7% of other gases; C2: CO2 14.9%, CH4 9.4%, O2 7.2% and 68.5% of other gases. Regarding the mass flows, there was an increase between the two campaigns (mean values): 2.5 x 10-3 and 3.6 x 10-3 g/m2.s of CH4 (C1 and C2, respectively), and 1.2 x 10-2 and 1.5 x 10-2 g/m2.s of CO2 (also for C1 and C2, respectively). The volumetric flows were the following (mean values): 4.0 x 10-6 and 5.7 x 10-6 m3/m2.s of CH4 (C1 and C2); and 7.0 x 10-6 and 8.8 x 10-6 m3/m2.s of CO2 (C1 and C2). The flows were within the ranges reported in the literature. Regarding the grass crops, it was observed that even though they were planted on a typical landfill soil without any special soil or cultivation treatment, the seeds of all five studied grasses germinated within the expected biological times. These species survived on the soil of the landfill yet presented smaller plant development indicators than those reported in the literature. The negative effect of an extreme soil compaction and low soil fertility contributed to such lower developmental results. Each crop showed a different ability to prevent gas emissions through the cover layer. We present them in descending order (mean values), namely: Mombasa (2.6% and 3.8% of CH4 in C1/C2, and 4.6% and 6.0% of CO2 in C1/ C2); Massai (2.0% and 2.8% of CH4, and 3.5% and 4.5% of CO2); Andropogon (1.1% and 1.5% of CH4, 1.9% and 2.5% of CO2); Bermuda (0.9% and 1.3% of CH4, 1.6% and 2.0% of CO2); and Buffel (0.4% and 0.6% of CH4, 0.5% and 0.6% of CO2). The volumetric and mass flows were lower in the soil planted with Mombasa grass and higher in that planted with Buffel. This was related to the main morphogenesis, structural, nutritional and productive features used in the assessment of crop survival and development.

Apresenta uma revisão sobre os conceitos teóricos de solos não saturados e sobre camadas de cobertura de Aterro. Ressalta a tecnologia de utilização de camadas evapotranspirativas e apresenta os tipos existentes desta camada. / It is a review about the non saturated soils concepts and waste landfill cover system. It points out the technology of using evaptranspirative cover systems and presents the existing kinds of this covers.

Apresenta uma revisão sobre os conceitos teóricos de solos não saturados e sobre camadas de cobertura de Aterro. Ressalta a tecnologia de utilização de camadas evapotranspirativas e apresenta os tipos existentes desta camada. / It is a review about the non saturated soils concepts and waste landfill cover system. It points out the technology of using evaptranspirative cover systems and presents the existing kinds of this covers.

Subtitle D of the Resource Conservation and Recovery Act (RCRA) requires a post closure period of 30 years for non hazardous wastes in landfills. Post closure care (PCC) activities under Subtitle D include leachate collection and treatment, groundwater monitoring, inspection and maintenance of the final cover, and monitoring to ensure that landfill gas does not migrate off site or into on site buildings. The decision to reduce PCC duration requires exploration of a performance based methodology to Florida landfills. PCC should be based on whether the landfill is a threat to human health or the environment. Historically no risk based procedure has been available to establish an early end to PCC. Landfill stability depends on a number of factors that include variables that relate to operations both before and after the closure of a landfill cell. Therefore, PCC decisions should be based on location specific factors, operational factors, design factors, post closure performance, end use, and risk analysis. The question of appropriate PCC period for Florida’s landfills requires in depth case studies focusing on the analysis of the performance data from closed landfills in Florida. Based on data availability, Davie Landfill was identified as case study site for a case by case analysis of landfill stability. The performance based PCC decision system developed by Geosyntec Consultants was used for the assessment of site conditions to project PCC needs. The available data for leachate and gas quantity and quality, ground water quality, and cap conditions were evaluated. The quality and quantity data for leachate and gas were analyzed to project the levels of pollutants in leachate and groundwater in reference to maximum contaminant level (MCL). In addition, the projected amount of gas quantity was estimated. A set of contaminants (including metals and organics) were identified as contaminants detected in groundwater for health risk assessment. These contaminants were selected based on their detection frequency and levels in leachate and ground water; and their historical and projected trends. During the evaluations a range of discrepancies and problems that related to the collection and documentation were encountered and possible solutions made. Based on the results of PCC performance integrated with risk assessment, projection of future PCC monitoring needs and sustainable waste management options were identified. According to these results, landfill gas monitoring can be terminated, leachate and groundwater monitoring for parameters above MCL and surveying of the cap integrity should be continued. The parameters which cause longer monitoring periods can be eliminated for the future sustainable landfills. As a conclusion, 30 year PCC period can be reduced for some of the landfill components based on their potential impacts to human health and environment (HH&E).

Esta pesquisa apresenta uma revisão bibliográfica sobre as emissões de metano em aterros sanitários, os conceitos de geração de gases em aterros sanitários, movimentações de gases em aterro, apresenta os métodos de medição de gases in situ, tipos de cobertura finais para aterros e a oxidação do metano na camada de cobertura. A pesquisa também tem como objetivo medir as emissões de gases e avaliar a infiltração das águas pluviais através da camada de cobertura do aterro sanitário da CTR Nova Iguaçu. As medições foram realizadas nos meses de julho a novembro de 2010, na camada de cobertura monolítica existente e em outra construída sobre uma barreira capilar. Sensores para medir temperatura e umidade foram instalados em profundidade nas duas camadas. Foram realizados ensaios de placa de fluxo para medir a composição dos gases e o fluxo através dos dois tipos de camadas, e avaliadas duas situações: com os poços de extração de gás ativos e desligados. Os sensores indicaram que em período de baixa pluviosidade, a barreira capilar apresenta uma eficácia superior à camada monolítica, e com a intensificação das chuvas, as umidades medidas nos dois tipos de camadas aumentam, e na barreira capilar o gradiente estabelecido entre os sensores diminui, indicando uma possível tendência à saturação desta barreira capilar. Porém, com a paralisação das chuvas, recupera e retoma sua condição inicial. Os resultados de medidas dos gases demostraram a eficiência do sistema de extração de gás quando ativado, resultando em emissões quase nulas de metano e gás carbônico nos dois tipos de camadas. No entanto, quando o sistema está desativado, as emissões através da camada monolítica são cerca de 3 vezes maiores do que através da barreira capilar. / This research presents a literature review on methane emissions from landfills, the concepts of landfill gas generation, the landfill internal gas flow, introduces the methods of measurement of gases "in situ", types of final landfill coverage and the methane oxidation in the cover layer. The research also purposes to measure greenhouse gas emissions and to evaluate the infiltration of rainwater through the landfill cover layer of the CTR Nova Iguaçu. Measurements were made in the months from July to November 2010, the existing monolithic cover layer and another built on a capillary barrier. Sensors to measure temperature and humidity were installed in two layers in depth. Plate assays were performed to measure the flow of the gas composition and flow through the two types of layers, and evaluated two situations with the gas extraction wells active and off. The sensors have indicated that in times of low rainfall, the capillary barrier has superior efficacy to the monolithic layer, and with the intensification of rain, the moisture content measured on two types of layers increase, the capillary barrier and the gradient established between sensors decreases, indicating a possible trend to saturation of capillary barrier. However, with the stoppage of rain, recovers and returns to its initial condition. The results of measurements of gases demonstrated the efficiency of extraction of gas when activated, resulting in near zero emissions of methane and carbon dioxide in the two types of layers. However, when the system is off, the emissions through the monolithic layer is about three times larger than through the capillary barrier.

Este trabalho apresenta uma revisão bibliográfica sobre os conceitos de solos não saturados e descreve os diversos tipos de camada de cobertura usadas em aterro de resíduos sólidos urbanos. Apresenta trabalhos científicos que contemplam curvas características de solos tropicais brasileiros. Caracteriza o solo usado antigamente como camada de cobertura do Aterro Morro do Céu e este solo com adição de 5% de bentonita. Determina a curva característica desses dois solos pelo Método do Papel Filtro e pela Placa de Sucção e, em seguida, Placa de Pressão. As curvas obtidas por esses métodos apresentaram diferenças. A adição da bentonita no solo teve como objetivo avaliar o desempenho do mesmo. O solo com adição de bentonita apresentou maior plasticidade, menor permeabilidade e maior capacidade de retenção de água no solo. Apresenta a modelagem de camadas monolíticas, camadas monolíticas evapotranspirativas, barreiras capilares, barreiras capilares evapotranspirativas através do uso do Programa VADOSE/W como ferramenta para aferição. / This study is a review about unsatured soils concepts and describes some types of soil cover systems used in landfills. It presents scientific works about Brazilian tropical soils Water Retention Curve. It characterizes the soil that was used as a cover layer system used at Morro do Céu landfill and the same soil with addition of 5% of bentonite. It determinates the soil water retention curve by Filter Paper Method and Suction Plate and, after that, Pressure Plate. The curves obtained by these two methods showed differences. The objective of the addition of the bentonite in the soil is to evaluate its performance. The soil with the addition of bentonite shows higher plasticity, lower hydraulic conductivity and higher moisture storage. It presents the modeling of monolithic covers, evapotranspirative monolithic covers, capillary barriers and evapotranspirative capillary barriers by the use of VADOSE/W Program as a tool for gauging.

Esta pesquisa apresenta uma revisão bibliográfica sobre as emissões de metano em aterros sanitários, os conceitos de geração de gases em aterros sanitários, movimentações de gases em aterro, apresenta os métodos de medição de gases in situ, tipos de cobertura finais para aterros e a oxidação do metano na camada de cobertura. A pesquisa também tem como objetivo medir as emissões de gases e avaliar a infiltração das águas pluviais através da camada de cobertura do aterro sanitário da CTR Nova Iguaçu. As medições foram realizadas nos meses de julho a novembro de 2010, na camada de cobertura monolítica existente e em outra construída sobre uma barreira capilar. Sensores para medir temperatura e umidade foram instalados em profundidade nas duas camadas. Foram realizados ensaios de placa de fluxo para medir a composição dos gases e o fluxo através dos dois tipos de camadas, e avaliadas duas situações: com os poços de extração de gás ativos e desligados. Os sensores indicaram que em período de baixa pluviosidade, a barreira capilar apresenta uma eficácia superior à camada monolítica, e com a intensificação das chuvas, as umidades medidas nos dois tipos de camadas aumentam, e na barreira capilar o gradiente estabelecido entre os sensores diminui, indicando uma possível tendência à saturação desta barreira capilar. Porém, com a paralisação das chuvas, recupera e retoma sua condição inicial. Os resultados de medidas dos gases demostraram a eficiência do sistema de extração de gás quando ativado, resultando em emissões quase nulas de metano e gás carbônico nos dois tipos de camadas. No entanto, quando o sistema está desativado, as emissões através da camada monolítica são cerca de 3 vezes maiores do que através da barreira capilar. / This research presents a literature review on methane emissions from landfills, the concepts of landfill gas generation, the landfill internal gas flow, introduces the methods of measurement of gases "in situ", types of final landfill coverage and the methane oxidation in the cover layer. The research also purposes to measure greenhouse gas emissions and to evaluate the infiltration of rainwater through the landfill cover layer of the CTR Nova Iguaçu. Measurements were made in the months from July to November 2010, the existing monolithic cover layer and another built on a capillary barrier. Sensors to measure temperature and humidity were installed in two layers in depth. Plate assays were performed to measure the flow of the gas composition and flow through the two types of layers, and evaluated two situations with the gas extraction wells active and off. The sensors have indicated that in times of low rainfall, the capillary barrier has superior efficacy to the monolithic layer, and with the intensification of rain, the moisture content measured on two types of layers increase, the capillary barrier and the gradient established between sensors decreases, indicating a possible trend to saturation of capillary barrier. However, with the stoppage of rain, recovers and returns to its initial condition. The results of measurements of gases demonstrated the efficiency of extraction of gas when activated, resulting in near zero emissions of methane and carbon dioxide in the two types of layers. However, when the system is off, the emissions through the monolithic layer is about three times larger than through the capillary barrier.

Este trabalho apresenta uma revisão bibliográfica sobre os conceitos de solos não saturados e descreve os diversos tipos de camada de cobertura usadas em aterro de resíduos sólidos urbanos. Apresenta trabalhos científicos que contemplam curvas características de solos tropicais brasileiros. Caracteriza o solo usado antigamente como camada de cobertura do Aterro Morro do Céu e este solo com adição de 5% de bentonita. Determina a curva característica desses dois solos pelo Método do Papel Filtro e pela Placa de Sucção e, em seguida, Placa de Pressão. As curvas obtidas por esses métodos apresentaram diferenças. A adição da bentonita no solo teve como objetivo avaliar o desempenho do mesmo. O solo com adição de bentonita apresentou maior plasticidade, menor permeabilidade e maior capacidade de retenção de água no solo. Apresenta a modelagem de camadas monolíticas, camadas monolíticas evapotranspirativas, barreiras capilares, barreiras capilares evapotranspirativas através do uso do Programa VADOSE/W como ferramenta para aferição. / This study is a review about unsatured soils concepts and describes some types of soil cover systems used in landfills. It presents scientific works about Brazilian tropical soils Water Retention Curve. It characterizes the soil that was used as a cover layer system used at Morro do Céu landfill and the same soil with addition of 5% of bentonite. It determinates the soil water retention curve by Filter Paper Method and Suction Plate and, after that, Pressure Plate. The curves obtained by these two methods showed differences. The objective of the addition of the bentonite in the soil is to evaluate its performance. The soil with the addition of bentonite shows higher plasticity, lower hydraulic conductivity and higher moisture storage. It presents the modeling of monolithic covers, evapotranspirative monolithic covers, capillary barriers and evapotranspirative capillary barriers by the use of VADOSE/W Program as a tool for gauging.