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Formació, cursos, Esdeveniments i Seminaris

Reactive transport of solutes with pore-scale mixing limitation: Effective Lagrangian model and upcoming CFD investigations.

SEMINARIO GRUPO DE HIDROLOGIA SUBTERRÁNEA (UPC-CSIC)
 
 
A cargo de: Guillem Sole-Marí
 
Día:  Jueves 10 de Octubre
Hora: a las 12:15 h
Lugar: Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja


Abstract:
Non-reactive transport of solutes in porous media can be modeled (at least for low to moderate degrees of sub-scale heterogeneities) by the classical advection-dispersion-equation (ADE), with an upscaled dispersion coefficient that accounts for the local variability of sub-scale velocities. However, when chemical reactions are incorporated, reaction rates tend to be over-predicted. This is mainly due to the inability of the upscaled dispersion term in the ADE to treat spreading and mixing separately. That is, the implicit assumption of full-mixing at all scales below the scale of interest is often erroneous. A suitable model should be able to account for the local anti-correlated reactant concentration fluctuations that are generated during the macroscopic transport. What we propose is a particle-based method to simulate transport of solutes with mixing limitation at the local scale. Besides solute mass, particles also carry a local disequilibrium with respect to the macroscopic (averaged) concentration. The disequilibrium is naturally generated by the random displacements of particles, and relaxed by local mixing. Thus the local concentrations, which ultimately control the reactions, are not defined in the Eulerian space, but on particles instead. On the other hand, the averaged concentrations are well defined in space and controlled by the ADE. We show that the temporal evolution of the local concentration covariance in the proposed model is similar to Kapoor and Gelhar’s (1994) "concentration variance conservation equation". Then, we study the mixing state evolution for two simple cases of initial and boundary conditions, showing that the model reproduces the typical features and temporal scaling of physical systems. The proposed Lagrangian model is implemented to reproduce the laboratory experiment of Gramling et al. (2002). Our numerical results show close agreement with the experimental data for physically meaningful values of the parameters. Finally, we present the Computational Fluid Dynamics simulations that will be performed in order to validate the proposed model and to study the dependence of the model parameters on (i) the local Péclet number and (ii) the pore geometry.

 

Reductive dissolution of magnetite from iron mine tailings: potential impacts on coastal environments

 

a cargo de
 
Jordi Palau

Jueves 03 de Octubre a las 12:15 h
en
Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja


Abstract:

Adverse impacts of mine tailings on sediments and water quality are major worldwide environmental problems. Due to the environmental contamination associated with the deposition of mine tailings on land, an alternative option is submarine disposal, which is already performed in some countries. However, toxic effects on coastal sediments may result from the release of different metals (e.g. Cr, V, Cu, Zn, Ni) and metalloids (e.g. As) contained in the iron oxides (e.g. magnetite) in the tailings. At the moment, we have little knowledge on the microbial reductive dissolution of iron oxides under marine conditions and the related potential release of trace elements.
In this study, batch experiments were performed using a number of iron ore samples from Chilean and Swedish mines and a mine tailings sample. The goal was to study the extent and kinetics of magnetite bioreduction under marine conditions and the potential release of trace elements. The determined elemental composition of the magnetite in the tailings showed relatively high amounts of trace elements (e.g. Mn, Zn, Co) compared with those of the iron ore samples (LA-ICP-MS and EMPA analyses). This enrichment of trace elements in the tailings’ magnetite might occur during the separation process at the iron ore processing plant.
The batch experiments, which were prepared using synthetic seawater (pH 8.2), a marine microbial strain (Shewanella loihica) and lactate as electron donor and carbon source, were conducted at 10º C in the dark for up to 113 days. Samples were collected at different times to measure lactate, acetate, Fe(II) and trace element concentrations in solution. Based on the consumption of lactate and production of acetate and aqueous Fe(II), the magnitude of microbial reduction of Fe(III) was calculated using a geochemical model including Monod kinetics. Furthermore, the model was used to simulate and evaluate the release of the trace elements detected in solution (e.g. Mn, V, Ga, Cu and As).

Acid water – rock / Portland cement interaction and multicomponent reactive transport modeling


SEMINARIO GRUPO DE HIDROLOGIA SUBTERRÁNEA 
(UPC-CSIC)
 
 
A cargo de: Jordi Cama
 
Dia: Jueves 19 de Septiembre
Hora:a las 12:15 h
 
Lugar:Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja


Abstract:
This talk focuses on the benefits of using multicomponent reactive
transport modeling (MCRTM) to understand and quantify the interaction
between acid water and rocks or Portland cement (mortar, concrete) that
takes place during and after the injection of CO2 in deep aquifers
(geological CO2 storage) and in the treatment of acid mine drainage (AMD).

Incorporate biofilm into reactive transport modeling in porous media

SEMINARIO GRUPO DE HIDROLOGIA SUBTERRÁNEA (UPC-CSIC)

 

A cargo de: Jingjing Wang

Día: Jueves 12 de Septiembre
Hora: a las 12:15 h
 
Lugar: Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja


Abstract:

Reactive Transport modeling of organic contaminant in the presence of microorganisms in porous media is an important research area in biochemical and environmental engineering, e.g. bioremediation of groundwater and waste water treatment. It implies complex coupled processes, such as hydrodynamics biochemistry and heterogeneous reactions between different phases, on a wide variety of scales from pore scale to Darcy scale. Biofilms are a mixture of microorganisms and extracellular polymeric substance (EPS) attached to the surface of grains in porous media. Because of the low permeability of the biofilm, molecular diffusion is the only transport process and advection doesn’t take place. Moreover, it is the main place for bacterial metabolism.
In the presence of biofilm, species transport displays non equilibrium behavior due to diffusion, retardation and kinetic reactions. Both physical and mathematical theory has demonstrated that incorporating immobile biofilm phases into reactive transport is reasonable. Multirate Mass Transfer (MRMT) models consider tracer transport both in the mobile and immobile phase simultaneously with mass exchange between mobile and immobile regions through first order mass transfer. It avoids spatial discretization of the immobile domain, because it solves state variables of immobile zones as explicit functions of the state variables in the mobile domain, which facilitates incorporation of nonlinear phenomena, such as biochemical reactions. However, kinetic rates of biochemical reactions depend on species concentration in the immobile biofilm. Therefore, the incorporation of biochemical reactions into transport is still a challenge. By treating biochemical kinetics as source sink term for the species in the biofilm,

 

A long-term experiment for monitoring saltwater intrusion dynamics using time-lapse cross-hole ERT 

SEMINARIO GRUPO DE HIDROLOGIA SUBTERRÁNEA (UPC-CSIC)

 

A cargo de: Andrea Palacios (PhD Student)
Día: Jueves 05 de septiembre
Hora: a las 12:15 h
Lugar: Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja


Abstract:

Monitoring water salinity is critical for the management of water resources in coastal aquifers, because groundwater is exposed to and threatened by saltwater intrusion (SWI). The electrical conductivity (EC) of water is highly and positively correlated to water salinity, and pore water electrical conductivity contributes to the bulk electrical conductivity of rocks. Consequently, measurements of bulk EC are indirect measurements of water EC, and thus, of water salinity. Surface electrical resistivity tomography (ERT) is widely used for obtaining bulk EC models because it is minimally invasive and provides high spatial coverage, but it is also strongly affected by low resolution at depth. We hypothesize that the use of CHERT (cross-hole ERT) can partly overcome this resolution limitation since the electrodes are at depth, and the model will not lose resolution in the zone of interest. We have tested this hypothesis at the Argentona site, a highly instrumented site for the study of SWI and submarine groundwater discharge (SGD), located 40 km northeast of Barcelona. Five boreholes, equipped with permanent electrodes, allow the monitoring of SWI dynamics on a transect perpendicular to the coastline. The obtained bulk EC models prove that CHERT is, indeed, superior to surface ERT in terms of resolution and accuracy when measuring bulk EC. After two years of monitoring using CHERT, we observe long- and short-term variability in SWI related to seasonal dynamics, aquifer salinization attributed to long-term drought, and aquifer responses to meteorological phenomena such as heavy rains and storms. By comparing CHERT results with water EC from water samples and with bulk EC from electromagnetic logging tools, we conclude that CHERT is a reliable tool for monitoring SWI dynamics.

Lectura de tesis

LECTURA DE TESIS 

GRUPO DE HIDROLOGÍA SUBTERRANEA (Unidad Asociada UPC-CSIC)



 
Comunicamos,

El próximo 18 de julio de 2019 tendrá lugar la defensa de la Tesis Doctoral dentro del Programa de Doctorado en Ingeniería del Terreno;
On july 18th 2019, the following PhD. Thesis in Geothecnical Engineering and Geo-Sciences will be defended;


"Assessment of a groundwater system under global change scenarios: the case of Kwale (Kenya) "
 
Núria Ferrer Ramos
 
Thesis advisors: Albert Folch Sancho.

The defense will take place:
Thursday, july 18th 2019, 11:00 

Place:
UPC, Campus Nord
Building D2. Classroom: 212
C/Jordi Girona, 1-3
08034 Barcelona
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