Micromechanical insight into the undrained instability of granular materials: deformation characteristics of geomaterials.

There is no agreement between experimental researchers whether the point where a granular material responds with a large change of stresses, strains or excess pore water pressure given a prescribed small input of some of the same variables defines a straight line or a curve in the stress space. This line, known as the instability line, may also vary in shape and position if the onset of instability is measured from drained or undrained triaxial tests. Failure of granular materials, which might be preceded by the onset of instability, is a subject that the geotechnical engineers have to deal with in the daily practice, and generally speaking it is associated to different phenomena observed not only in laboratory tests but also in the field. Examples of this are the liquefaction of loose sands subjected to undrained loading conditions and the diffuse instability under drained loading conditions. This research presents results of DEM simulations of undrained triaxial tests with the aim of studying the influence of stress history and relative density on the onset of instability in granular materials. Micro-mechanical analysis including the evolution of coordination numbers and fabric tensors is performed aiming to gain further insight on the particle-scale interactions that underlie the occurrence of this instability. In addition to provide a greater understanding, the results presented here may be useful as input for macro-scale constitutive models that enable the prediction of the onset of instability in boundary value problems.

Exploring the effects of stress history on the drained and undrained cyclic behaviour of granular materials.

This paper presents the results of 3D DEM simulations of granular materials subject to cyclic loading. While both the drained and undrained conditions are considered, the effects of depositional history and consolidation stress history on the stress-strain response are specifically evaluated. It is demonstrated that the different stress histories have a significant effect on soil response and that such effects can be attributed to differences in the initial particle arrangement (fabric).

Evaluaci?n de la aplicaci?n de carb?n activado granular en la filtraci?n del agua clarificada del r?o Cauca

El constante deterioro de las fuentes h?dricas y su uso como recurso en el abastecimiento de agua para consumo humano han conllevado a la b?squeda de la optimizaci?n de los procesos de tratamiento de forma tal que se alcancen condiciones de agua segura con el menor riesgo posible de afectaciones a la salud de la poblaci?n. Es por esto que los sistemas de abastecimiento de agua potable han adoptado estrategias enmarcadas dentro de los planes de seguridad del agua mediante la reducci?n de la contaminaci?n en la fuente de abastecimiento, la remoci?n o reducci?n de diferentes contaminantes mediante los procesos de tratamiento y la prevenci?n de la contaminaci?n del agua en el sistema de almacenamiento y distribuci?n al usuario final. Al observar que la filtraci?n es una de las etapas m?s cr?ticas dentro del tratamiento por ser la ?ltima barrera f?sica para la remoci?n de part?culas presentes en el agua; se plante? este proyecto de grado para estudiar a escala de laboratorio el uso de carb?n activado granular en el proceso de filtraci?n de agua clarificada del Rio Cauca, con el fin de analizar la eficiencia de remoci?n de turbiedad y materia org?nica medida como UV254 y as? establecer el alcance de los valores l?mite recomendados por las entidades internacionales para la disminuci?n del riesgo microbiol?gico y el riesgo cr?nico que pueda estar asociado a la presencia de materia org?nica en el agua para consumo humano. Se emple? carb?n activado granular de origen bituminoso y arena en seis diferentes configuraciones como medio filtrante principal en la etapa de filtraci?n (50%CAG ? 50% Arena, 65% CAG ? 35% Arena, 75% CAG ? 25% Arena, 85% CAG ? 15% Arena, 90% CAG ? 10% Arena y 100% CAG). Se consider? adem?s una configuraci?n con antracita y arena (70% Antracita ? 30% Arena) para comparar el comportamiento de ambos materiales filtrantes en el tratamiento de agua resultante del proceso de clarificaci?n efectuado por la Planta de Tratamiento de Agua Potable Puerto Mallarino en la ciudad de Cali. Se emple? un sistema de filtraci?n en columnas con distribuci?n de agua mediante conducciones reguladas a un caudal constante de 12 mL/min. El efluente de cada unidad de filtros fue evaluado y comparado con el afluente mediante la medici?n de Color Aparente, Turbiedad, UV254, pH y Conductividad. Se obtuvo como resultado que la configuraci?n C5 con 90% de CAG y 10% Arena logr? una mayor estabilidad de la turbiedad obteniendo valores m?nimos por debajo de 2 UNT (MAVDT), 0.5 UNT (WHO) y 0.15 UNT (EPA) y aunque no tuvo diferencias significativas comparado con el filtro de Antracita y Arena, si present? un mejor desempe?o en la remoci?n de turbiedad debido al alcance de un mayor n?mero de datos por debajo de 0.3 UNT. En cuanto a la eficiencia de remoci?n de materia org?nica en el agua medida como UV254 se observaron mejores resultados para la configuraci?n C4 con 85% de CAG y 15% Arena y aunque las eficiencias de remoci?n de materia org?nica no fueron significativamente altas se observa claramente la ventaja que presenta el uso de CAG como medio filtrante adsorbente comparado con el medio convencional de Antracita y Arena. La obtenci?n de bajas eficiencias de remoci?n fue debido al contenido de material en suspensi?n ya que los filtros de CAG trabajaron en la retenci?n de dicho material afectando considerablemente la capacidad de adsorci?n. Mediante esta investigaci?n se comprob? que la selecci?n adecuada de las condiciones operacionales de los filtros de CAG puede generar agua comparativamente similar o superior a los filtros conformados con materiales convencionales como Antracita y arena. De igual forma, el uso de CAG como medio filtrante para el tratamiento de agua del Rio Cauca es un insumo que puede aportar a una posible estrategia para disminuir el riesgo microbiol?gico y el riesgo cr?nico asociado con el contenido de materia org?nica en el agua distribuida a la poblaci?n cale?a

Análise experimental e numérica do comportamento de estruturas de solo reforçado com geossintéticos : solo granular versus fino

As estruturas de solo reforçado com geossintéticos são normalmente constituídas por solos granulares com boas propriedades físicas e mecânicas. O uso de apenas este tipo de solos pode proporcionar o aumento, por vezes insustentável, do custo da execução das estruturas e o aumento do seu impacto ambiental. Deste modo, as estruturas de solo reforçado perdem a sua vantagem competitiva em relação a outros tipos de estruturas (muros de betão, muros de gravidade, muros de gabiões, etc.). Para resolver este problema podem ser utilizados outros tipos de solos (solos locais, finos, com propriedades físicas e mecânicas piores mas, no entanto, mais baratos) para a execução deste tipo de estruturas. De forma geral, com este estudo pretendeu-se contribuir para o incremento do conhecimento sobre a utilização de solos finos para a construção de estruturas de solo reforçado (muros e taludes). Para tal avaliaram-se as diferenças no comportamento mecânico dos materiais compósitos (solo granular reforçado versus solo fino reforçado) e das estruturas de solo reforçado constituídas com os dois tipos de solos. Assim, os objetivos deste estudo foram avaliar: a influência de vários parâmetros nas propriedades mecânicas e na capacidade de carga dos solos reforçados com geossintéticos; a influência de vários parâmetros no dimensionamento das estruturas de solo reforçado; e o comportamento das estruturas dimensionadas (incluindo a estabilidade global e a influência do processo construtivo) recorrendo a uma ferramenta numérica (PLAXIS). Para cumprir os objetivos propostos foram realizadas análises experimentais em laboratório (análise do comportamento do solo reforçado através de ensaios triaxiais e de California Bearing Ratio) e análises numéricas (dimensionamento de estruturas de solo reforçado; modelação numérica do comportamento através de uma ferramenta numérica comercial com o método dos elementos finitos). Os resultados dos ensaios experimentais mostraram que o comportamento mecânico e a capacidade de carga do solo foram incrementados com a inclusão das camadas de geossintético. Este efeito variou com os diversos parâmetros analisados mas, de forma geral, foi mais importante no solo fino (solo com propriedades mecânicas piores). As análises numéricas mostraram que as estruturas de solo fino precisaram de maior densidade de reforços para serem estáveis. Além disso, as estruturas de solo fino foram mais deformáveis e o efeito do seu processo construtivo foi mais importante (principalmente para estruturas de solo fino saturado).

Measuring nitrous oxide emissions from conventional and controlled release fertilisers in south-east Queensland pineapple production

Nitrous oxide (N2O) is a potent greenhouse gas with a global warming potential 298 times higher than carbon dioxide. Soils are a natural source of N2O, contributing 65% of global emissions. This paper is the first in Australia to measure and compare N2O emissions from pre-plant controlled release (CR) and conventional granular (CV) fertilisers in pineapple production using static PVC chambers to capture N2O emissions. Farm 1 cumulative emissions from the CR fertiliser were 3.22 kg ha-1 compared to 6.09 kg ha-1 produced by the CV. At farm 2 the CV blend emitted 2.36 kg ha-1 in comparison to the CR blend of 2.92 kg ha-1. Daily N2O flux rates showed a relationship of direct response to rainfall and soil moisture availability. High emissions were observed for wheel tracks where increased N2O emissions may be linked to soil compaction and waterlogging that creates anaerobic conditions after rain events. Emission measurements over three months highlighted the inconsistencies found in other studies relative to reducing emissions through controlled release nitrogen. More investigations are required to verify the benefits associated with controlled release fertiliser use in pineapples, placement and seasonal timing to address N2O emissions in pineapples.

Anaerobic digestion process for biogas and biomolecules production: microflora identification and characterization

The anaerobic process was efficient in organic matter removal. During the process, an interesting compound as quercetin was produced inside of reactor. Phylogenetic analysis showed the presence of phylotypes affiliated with gamma-Proteobacteria, Choroflexi, and Bacteroidetes. Archaea were represented by phylotypes belonging to the genus Methanosarcina and Methanosaeta.

Bioactive compounds through anaerobic digestion of heterotrophic microalgae residues

Several important biomolecules are available into anaerobically digested effluents that were obtained from the biodiesel production process using heterotrophically grown microalga Chlorella protothecoides. Defatted microalgae residues and crude glycerol may undergo anaerobic digestion, separately and in admixture, providing methane/hydrogen and a digestate exploitable for agriculture applications. Furthermore, industrial interesting bioactive compounds such as polyphenols provided with antioxidant activity can be obtained. Anaerobic process offers a promising chance and can be advantageously combined with algae lipid-extraction techniques in order to make it more sustainable.

Life cycle assessment of advanced bioethanol production from pulp and paper sludge

This work evaluates the environmental performance of using pulp and paper sludge as feedstock for the production of second generation ethanol. An ethanol plant for converting 5400 tons of dry sludge/year was modelled and evaluated using a cradle-to-gate life cycle assessment approach. The sludge is a burden for pulp and paper mills that is mainly disposed in landfilling. The studied system allows for the valorisation of the waste, which due to its high polysaccharide content is a valuable feedstock for bioethanol production. Eleven impact categories were analysed and the results showed that enzymatic hydrolysis and neutralisation of the CaCO3 are the environmental hotspots of the system contributing up to 85% to the overall impacts. Two optimisation scenarios were evaluated: (1) using a reduced HCl amount in the neutralisation stage and (2) co-fermentation of xylose and glucose, for maximal ethanol yield. Both scenarios displayed significant environmental impact improvements.

Segregation predictions for a binary mixture of granular material under flow conditions in a continuum mechanics framework

Abstract not available

Crassaminicella profunda gen. nov., sp nov., an anaerobic marine bacterium isolated from deep-sea sediments

A novel, anaerobic, chemo-organotrophic bacterium, designated strain Ra1766HT, was isolated from sediments of the Guaymas basin (Gulf of California, Mexico) taken from a depth of 2002 m. Cells were thin, motile, Gram-stain-positive, flexible rods forming terminal endospores. Strain Ra1766H(T) grew at temperatures of 25-45 degrees C (optimum 30 degrees C), pH 6.7-8.1 (optimum 7.5) and in a salinity of 5-60 g l(-1) NaCl (optimum 30 g l(-1)). It was an obligate heterotrophic bacterium fermenting carbohydrates (glucose and mannose) and organic acids (pyruvate and succinate). Casamino acids and amino acids (glutamate, aspartate and glycine) were also fermented. The main end products from glucose fermentation were acetate, butyrate, ethanol, H-2 and CO2. Sulfate, sulfite, thiosulfate, elemental sulfur, fumarate, nitrate, nitrite and Fe(III) were not used as terminal electron acceptors. The predominant cellular fatty acids were C-14 : 0, C-16:1 omega 7, C-16:1 omega 7 DMA and C-16:0. The main polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phospholipids. The G +C content of the genomic DNA was 33.7 molo/o. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Ra1766H(T) was affiliated to cluster XI of the order Clostridia les, phylum Firmicutes. The closest phylogenetic relative of Ra1766H(T) was Geosporobacter subterraneus (94.2% 16S rRNA gene sequence similarity). On the basis of phylogenetic inference and phenotypic properties, strain Ra1766H(T) (=DSM 27501(T)=JCM 19377(T)) is proposed to be the type strain of a novel species of a novel genus, named Crassaminicella pro funda.

Anaerobic oxidation of methane at a marine methane seep in a forearc sediment basin off Sumatra, Indian Ocean

A cold methane seep was discovered in a forearc sediment basin off the island Sumatra, exhibiting a methane-seep adapted microbial community. A defined seep center of activity, like in mud volcanoes, was not discovered. The seep area was rather characterized by a patchy distribution of active spots. The relevance of anaerobic oxidation of methane (AOM) was reflected by C-13-depleted isotopic signatures of dissolved inorganic carbon. The anaerobic conversion of methane to CO2 was confirmed in a C-13-labeling experiment. Methane fueled a vital microbial community with cell numbers of up to 4 x 10(9) cells cm(-3) sediment. The microbial community was analyzed by total cell counting, catalyzed reporter deposition fluorescence in situ hybridization (CARD FISH), quantitative real-time PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). CARD FISH cell counts and qPCR measurements showed the presence of Bacteria and Archaea, but only small numbers of Eukarya. The archaeal community comprised largely members of ANME-1 and ANME-2. Furthermore, members of the Crenarchaeota were frequently detected in the DGGE analysis. Three major bacterial phylogenetic groups (delta-Proteobacteria, candidate division OP9, and Anaerolineaceae) were abundant across the study area. Several of these sequences were closely related to the genus Desulfococcus of the family Desulfobacteraceae, which is in good agreement with previously described AOM sites. In conclusion, the majority of the microbial community at the seep consisted of AOM-related microorganisms, while the relevance of higher hydrocarbons as microbial substrates was negligible.

Towards a better understanding of granular material processes: The coupling of a computational fluid dynamics framework with micro-mechanical models

Abstract not available

Object-Oriented Modeling Simulation and Control of Activated Sludge Process

Object-oriented modeling is spreading in current simulation of wastewater treatments plants through the use of the individual components of the process and its relations to define the underlying dynamic equations. In this paper, we describe the use of the free-software OpenModelica simulation environment for the object-oriented modeling of an activated sludge process under feedback control. The performance of the controlled system was analyzed both under normal conditions and in the presence of disturbances. The object-oriented described approach represents a valuable tool in teaching provides a practical insight in wastewater process control field.

CERAMIC MATERIAL FROM SEWAGE SLUDGE AS SUPPORT MATERIAL SUPPLY WATER FILTRATION

This study shows a possibility of using municipal sewage sludge after thermal treatment in the production of a filtering material to water treatment. Due to the fast urbanization and implementation of high standards for effluent in many countries in recent years, the sewage sludge is being produced in an ever increasing amount. Therefore, the use of sludge is a suitable solution for the expected large quantity of sludge. Dehydration of sludge was performed by controlled heating at temperatures of 1100 degrees C, 850 degrees C, 650 degrees C, 350 degrees C for 3 hours. After thermal treatment the sludge was characterized by X-ray fluorescence, TG/DTG/DTA, residue solubilization and residue lixiviation tests. The aim of the present work was to observe, thought the characterization techniques, if the treated sewage sludge is or not adequate to be used as filter material to water treatment. It will be verified which treatment temperature of the sludge offer possibility to its use in water treatment without carrying pollutants in concentrations out of the standards.