Physicochemical parameters in the generation of turbidity episodes in a water supply distribution system

This research was funded by EMALCSA. Agreement between EMALCSA and the University of Coruña (FUAC). Project INV01819/2019-2022.[Abstract:] Water is necessary for the development and support of human life. The ability of water to supply the different populations has different origins: water taken from river diversions, water from underground catchments, water from lakes and reservoirs, water from the recirculation of treated water, etc. Episodes of turbidity and color changes in the water supply in pipe distribution systems are non-isolated problems that occur in many cities and towns. In particular, sedimentation in water supply pipelines and the subsequent resuspension of these particles in the system have created the need to investigate the processes and variables that promote turbidity episodes, including why, when, and where these episodes occur. In this study, different physicochemical parameters were investigated and analyzed in the water supply distribution network of the city of La Coruña (northwest Spain) through a pipe monitoring panel under real operating conditions. The supply waters come from the Mero river basin, a basin made up of siliceous materials, a unique condition with respect to the majority of studies that have been carried out using waters coming from basins made of basic materials. In this case, the relationships between different variables were studied, including the number of particles, particle size, turbidity, color, concentration of particulate materials, and mineralogy. In this article, only those parameters that are better correlated have been noted. The results revealed a predominant relationship between color and the concentration and mineralogy of particulate materials, as well as between turbidity and the number and size of particles

Therapeutic characteristics of Galician mineral and thermal waters (NW-Spain) ascribed to their local/regional geological setting

[Abstract] Galicia is located in the NW corner of the Iberian Peninsula (Spain). From a geological point of view, the territory belongs to the Hercynian chain and, more specifically, to a large outcrop dominated by igneous and metamorphic rocks called the Hesperian Massif or Iberian Massif. In some sectors the Hesperian Massif is partially covered by more recent sedimentary deposits. The geology of Galicia is very complex due to the age of the rocks that make up its substrate and their diversity. Thus, the hydrogeological behaviour of the underground medium (hydrodynamic and hydrogeochemical characteristics) will determine the therapeutic properties of the water emanating from the surface. In Galicia, aquifers are generally shallow with low mineralization, except for those whose waters come from deep fractured mediums. The chemical characteristics of the water are directly related to the geological matrix. The groundwater flows through the geological medium and is mineralogically enriched by heterogeneous chemical reactions. Galicia turns out to be an area rich in the potential exploitation, applications and use of different water resources. These resources are thermal, mineral-natural and mineral-medicinal waters. In this work, we have developed a study that relates the geology, hydrogeological and hydrogeochemica

Size Effect and Other Effects on Mode I Fracture Toughness Using Two Testing Methods

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] Mode I fracture toughness (KIC) is an intrinsic material property that quantifies its resistance to tensile fracture propagation. The International Society for Rock Mechanics has endorsed four methods to determine the KIC of rock, namely, the short rod, chevron bend, cracked chevron notched Brazilian disc, and semi-circular bend (SCB) methods. In this study, we compare the results of the SCB technique with those of the recently proposed pseudo-compact tension (pCT) test, which has proven to be convenient for the assessment of KIC in both fragile and ductile rocks. We select the SCB as a benchmark method due to its popularity, simplicity, and straightforward testing configuration. We discuss the results of 146 tests performed with different lithologies (Arcera, Pinacas and Corvio sandstones, and Blanco Mera granite), different sample sizes (100, 50 and 38 mm diameter), and a range of notch lengths. We also assess test repeatability and intercomparability of the results obtained using the two techniques. Compared with the SCB test, the pCT test allows for improved control of the specimen behaviour after the peak load, which provides a greater wealth of fracture mechanics information. pCT specimens yield results with higher repeatability than SCB samples. Although we observe that KIC tends to decrease with an increase in the notch length ratio, this effect appears to be non-significant based on statistical assessments. Accordingly, the corresponding mean KIC values are comparable for medium- and large specimens. The influence of specimen size is more pronounced in the SCB tests, while the pCT tests show less dependence for harder lithologies. Therefore, to set up minimum specimen requirements for fracture toughness testing, in addition to geometrical constraints, some key lithology-dependent properties (strength, mineralogy, grain size, etc.) should also be considered. Further methodological considerations related to test execution are also discussed.This work was funded by Repsol S.A. and supported by the Xunta de Galicia, the European Union (European Social Fund - ESF) and the MINECO/AEI/FEDER EU project BIA2017-87066-R. Funding for open access charge: Universidade da Coruña/CISUG

Formulación numérica en elementos finitos de problemas de flujo multifásico no isotermo y transporte de solutos reactivos en medios porosos

En este artículo se presenta la formulación numérica del flujo multifásico no isotermo y del transporte reactivo de un sistema multicomponente de solutos en condiciones no isotermas. El modelo numérico ha sido implementado en un código (FADES-CORE c ?) el cual ha sido verificado y validado. En este artículo se describe el esquema de resolución utilizado y las distintas variantes del mismo. Para la discretización temporal se ha formulado un algoritmo de optimización del paso de tiempo autom´atico. Por último se incluye un ejemplo de validación del correcto funcionamiento del modelo.Peer Reviewe

Analysis and evaluation of groundwater protection alternatives during waste extraction operations (acid tars) in a lagoon in Arganda del Rey (Madrid)

[Resumen:] La Comunidad de Madrid está llevando a cabo la restauración integral de una antigua gravera contaminada con residuos peligrosos, mayoritariamente sulfonatos de petróleo (alquitranes ácidos), procedentes del tratamiento de aceites industriales usados. Parte de dichos vertidos, realizados en las décadas de los años 1970 y 1980, se depositaron en una laguna originada por la explotación de áridos por debajo del nivel piezométrico del acuífero, conformando una balsa con 50000 m3 de residuos peligrosos. La diversa ubicación, naturaleza y estado de los residuos requiere diferentes soluciones para su extracción y tratamiento, por lo que el proyecto de restauración consta de varias fases. Los residuos depositados producen un efecto de confinamiento en el acuífero, dado que la cota del fondo de los residuos es inferior al nivel piezométrico. Con estos condicionantes es crítico establecer un procedimiento de protección de las aguas subterráneas a la hora de acometer la próxima fase, consistente en la extracción de los residuos situados por debajo del nivel piezométrico. En este artículo se describe el proceso que se ha llevado a cabo para seleccionar la mejor alternativa desde el punto de vista hidrogeológico, considerando todos los datos disponibles obtenidos en las fases previas del proyecto. Una vez planteadas y caracterizadas todas las alternativas posibles se ha seleccionado de forma argumentada y razonada como mejor alternativa la realización de una barrera impermeabilizante perimetral a la balsa y empotrada en una capa de arcillas de 2 m de espesor situada en el subsuelo de la balsa.[Abstract:] The Community of Madrid is carrying out the integral restoration of an old gravel pit contaminated with hazardous waste, mostly petroleum sulphonates (acid tars), from the treatment of used industrial oil. Part of these discharges, from the 1970s and 1980s, were deposited in a lagoon generated by the exploitation of aggregates below the piezometric level of the aquifer, forming a raft with 50,000 m3 of hazardous waste. The different locations, nature and conditions of the waste require different solutions for its extraction and treatment, so the restoration project consists of several phases. The deposited waste produces an effect of confinement in the aquifer, since the bottom level of the waste is lower than the piezometric level. With these conditions, it is critical to establish a procedure for the protection of the groundwater when executing the next phase, consisting of the extraction of waste located below the piezometric level. This article describes the process that has been carried out to select the best alternative from a hydrogeological point of view, considering all the available data obtained in the previous phases of the project. Once all the possible alternatives had been considered and characterized in a reasoned way, we chose the construction of a perimeter barrier around the raft embedded in a clay layer of 2 m thick located in the base of the raft as the best option

Physicochemical Parameters in the Generation of Turbidity Episodes in a Water Supply Distribution System

Water is necessary for the development and support of human life. The ability of water to supply the different populations has different origins: water taken from river diversions, water from underground catchments, water from lakes and reservoirs, water from the recirculation of treated water, etc. Episodes of turbidity and color changes in the water supply in pipe distribution systems are non-isolated problems that occur in many cities and towns. In particular, sedimentation in water supply pipelines and the subsequent resuspension of these particles in the system have created the need to investigate the processes and variables that promote turbidity episodes, including why, when, and where these episodes occur. In this study, different physicochemical parameters were investigated and analyzed in the water supply distribution network of the city of La Coruña (northwest Spain) through a pipe monitoring panel under real operating conditions. The supply waters come from the Mero river basin, a basin made up of siliceous materials, a unique condition with respect to the majority of studies that have been carried out using waters coming from basins made of basic materials. In this case, the relationships between different variables were studied, including the number of particles, particle size, turbidity, color, concentration of particulate materials, and mineralogy. In this article, only those parameters that are better correlated have been noted. The results revealed a predominant relationship between color and the concentration and mineralogy of particulate materials, as well as between turbidity and the number and size of particles

A comparison of results obtained with two subsurface non-isothermal multiphase reactive transport simulators, FADES-CORE and TOUGHREACT

FADES-CORE and TOUGHREACT are codes used to model the non-isothermal multiphase flow with multicomponent reactive transport in porous media. Different flow and reactive transport problems were used to compare the FADES-CORE and TOUGHREACT codes. These problems take into account the different cases of multiphase flow with and without heat transport, conservative transport, and reactive transport. Consistent results were obtained from both codes, which use different numerical methods to solve the differential equations resulting from the various physicochemical processes. Here we present the results obtained from both codes for various cases. Some results are slightly different with minor discrepancies, which have been remedied, so that both codes would be able to reproduce the same processes using the same parameters. One of the discrepancies found is related to the different calculation for thermal conductivity in heat transport, which affects the calculation of the temperatures, as well as the pH of the reaction of calcite dissolution problem modeled. Therefore it is possible to affirm that the pH is highly sensitive to temperature. Generally speaking, the comparison was concluded to be highly satisfactory, leading to the complete verification of the FADES-CORE code. However, we must keep in mind that, as there are no analytical solutions available with which to verify the codes, the TOUGHREACT code has been thoroughly corroborated, given that the only possible way to prove that the code simulation is correct, is by comparing the results obtained with both codes for the identical problems, or to validate the simulation results with actual measured data

A comparison of results obtained with two subsurface non-isothermal multiphase reactive transport simulators, FADES-CORE and TOUGHREACT

FADES-CORE and TOUGHREACT are codes used to model the non-isothermal multiphase flow with multicomponent reactive transport in porous media. Different flow and reactive transport problems were used to compare the FADES-CORE and TOUGHREACT codes. These problems take into account the different cases of multiphase flow with and without heat transport, conservative transport, and reactive transport. Consistent results were obtained from both codes, which use different numerical methods to solve the differential equations resulting from the various physicochemical processes. Here we present the results obtained from both codes for various cases. Some results are slightly different with minor discrepancies, which have been remedied, so that both codes would be able to reproduce the same processes using the same parameters. One of the discrepancies found is related to the different calculation for thermal conductivity in heat transport, which affects the calculation of the temperatures, as well as the pH of the reaction of calcite dissolution problem modeled. Therefore it is possible to affirm that the pH is highly sensitive to temperature. Generally speaking, the comparison was concluded to be highly satisfactory, leading to the complete verification of the FADES-CORE code. However, we must keep in mind that, as there are no analytical solutions available with which to verify the codes, the TOUGHREACT code has been thoroughly corroborated, given that the only possible way to prove that the code simulation is correct, is by comparing the results obtained with both codes for the identical problems, or to validate the simulation results with actual measured data