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  • Investigation of the dielectric properties of nanofiltration membranes

     Oatley, Darren Lee; Llenas Argelaguet, Laia; Aljohani, Nasser H M; Williams, Paul Melvyn; Martínez Lladó, Xavier; Rovira Boixaderas, Miquel; Pablo Ribas, Joan de
    Desalination
    Date of publication: 2013-04-15
    Journal article

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    Membrane nanofiltration is extremely complex and is dependent on the micro-hydrodynamics and interfacial events occurring at the membrane surface and within the membrane nanopores. There is significant debate as to the exact nature of these complex phenomena and rejection is typically attributed to a combination of steric and electrical effects. The electrical effects are less well understood and in particular the contribution of dielectric exclusion. There is a real need to determine a suitable description for dielectric exclusion for use in membrane modelling for the ab initio design and development of new membrane separation processes and for the scale up and optimisation of existing processes. In this paper the currently accepted separation mechanisms of membrane nanofiltration are explored in order to justify the use of porous models. Furthermore, the Desal-5-DK membrane is characterised by performing a series of rejection experiments of 0.01 M salt solutions at the membrane isoelectric point. This has the advantage of effectively neutralising the membrane fixed charge and facilitating an independent study of the dielectric partitioning at the membrane surface. A simplistic model based on Born theory was tested and found to be remarkably accurate, indicating that ion solvation may be the appropriate dielectric exclusion mechanism for true nanofiltration membranes

  • Uranium speciation studies at alkaline pH and in the presence of hydrogen peroxide using time-resolved laser-induced fluorescence spectroscopy

     Martinez Torrents, Albert; Meca, Sandra; Baumann, Nils; Marti Gregorio, Vicenç; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Casas Pons, Ignasi
    Polyhedron
    Date of publication: 2013-05
    Journal article

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    Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to study the speciation of uranium(VI) at very alkaline pH (11-13), at room temperature and in the absence of CO2. In this case, at pH = 11, two different fluorescence lifetimes appeared, which were attributed to the species UO2(OH)(3)(-) and (UO2)(3)(OH)(7)(-). At pH = 13, no fluorescence was detected, indicating that the predominant species, UO2(OH)(4)(2-), is not fluorescent. At pH = 12, the lifetime obtained is attributed to the predominant species UO2(OH)(3). Because of the absence of fluorescence of the UO2(OH)(4)(2-) species at room temperature, measurements at 10 K were made, obtaining two different lifetimes in the pH range between 12 and 13.5, indicating the presence of two different species: UO2(OH)(3)(-) and UO2(OH)(4)(2-). The difference between the lifetimes allowed the calculation of the contribution of each species to the total fluorescence signal intensity. From the experiments carried out in the presence of hydrogen peroxide, it was observed that hydrogen peroxide produces a quenching effect to the fluorescence of the uranium species. At pH 12 the quenching is static, which points to the formation of a non-fluorescent complex between U(VI) and hydrogen peroxide. Using the Stern-Volmer equation for static quenching, the equilibrium formation constant of the first species, UO2O2(OH)(2)(2-), was calculated to be logK(0) = 28.7 +/- 0.4, which is similar to the one determined using UV-Visible spectrometry, 28.1 +/- 0.2 Meca et al. (2011) [42]. (C) 2013 Elsevier Ltd. All rights reserved.

    Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to study the speciation of uranium(VI) at very alkaline pH (11–13), at room temperature and in the absence of CO2. In this case, at pH = 11, two different fluorescence lifetimes appeared, which were attributed to the species UO2(OH)3− and (UO2)3(OH)7−. At pH = 13, no fluorescence was detected, indicating that the predominant species, UO2(OH)42−, is not fluorescent. At pH = 12, the lifetime obtained is attributed to the predominant species UO2(OH)3−. Because of the absence of fluorescence of the UO2(OH)42− species at room temperature, measurements at 10 K were made, obtaining two different lifetimes in the pH range between 12 and 13.5, indicating the presence of two different species: UO2(OH)3− and UO2(OH)42−. The difference between the lifetimes allowed the calculation of the contribution of each species to the total fluorescence signal intensity. From the experiments carried out in the presence of hydrogen peroxide, it was observed that hydrogen peroxide produces a quenching effect to the fluorescence of the uranium species. At pH 12 the quenching is static, which points to the formation of a non-fluorescent complex between U(VI) and hydrogen peroxide. Using the Stern–Volmer equation for static quenching, the equilibrium formation constant of the first species, UO2O2(OH)22−, was calculated to be logK0 = 28.7 ± 0.4, which is similar to the one determined using UV–Visible spectrometry, 28.1 ± 0.2 Meca et al. (2011) [42].

  • Dynamic leaching studies of 48 MWd/kgU UO2 commercial spent nuclear fuel under oxic conditions

     Serrano Purroy, D.; Casas Pons, Ignasi; Gonzalez Robles, E.; Glatz, Jean Paul; Wegen, D.H.; Clarens Blanco, Frederic; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Martínez Esparza, A.
    Journal of nuclear materials
    Date of publication: 2013-03
    Journal article

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    The leaching of a high-burn-up spent nuclear fuel (48 MWd/KgU) has been studied in a carbonate-containing solution and under oxic conditions using a Continuously Stirred Tank Flow-Through Reactor (CSTR). Two samples of the fuel, one prepared from the centre of the pellet (labelled CORE) and another one from the fuel pellet periphery, enriched with the so-called High Burn-Up Structure (HBS, labelled OUT) have been used. For uranium and actinides, the results showed that U, Np, Am and Cm gave very similar normalized dissolution rates, while Pu showed slower dissolution rates for both samples. In addition, dissolution rates were consistently two to four times lower for OUT sample compared to CORE sample. Considering the fission products release the main results are that Y, Tc, La and Nd dissolved very similar to uranium; while Cs, Sr, Mo and Rb have up to 10 times higher dissolution rates. Rh, Ru and Zr seemed to have lower dissolution rates than uranium. The lowest dissolution rates were found for OUT sample. Three different contributions were detected on uranium release, modelled and attributed to oxidation layer, fines and matrix release.

  • Anaerobic digestion of animal by-products. Pre-treatments and co-digestion

     Rodríguez Abalde, Ángela
    Defense's date: 2013-11-18
    Department of Agri-Food Engineering and Biotechnology, Universitat Politècnica de Catalunya
    Theses

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  • Study of methods for the improvement of the anaerobic digestion of lipids and long chain fatty acids  Open access

     Affes, Rim
    Defense's date: 2013-05-14
    Department of Agri-Food Engineering and Biotechnology, Universitat Politècnica de Catalunya
    Theses

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    Anaerobic digestion is a biochemical process that transforms diverse categories of biomass feedstock to renewable energy, in the form of methane, and contributes to resources conservation and greenhouse gases emission mitigation. Lipid-rich waste and wastewaters have a high energy potential, however efficient methane recovery with conventional anaerobic digestion technology is not easy to achieve because of a wide assortment of operational problems mainly related to the accumulation of long chain fatty acids (LCFA), products of lipids hydrolysis, in the system. The objective of the present dissertation is to test and to evaluate new methodologies and strategies to improve the anaerobic digestion of high-strength lipid waste. In a preliminary approach, the suitability and the attractiveness of high-strength lipid wastes and slaughterhouse wastes for biogas production was confirmed, suffice to control the applied organic load. The obtained results reinforced the existing knowledge describing the flotation and wash-out of substrate/biomass and the inhibition phenomena affecting the microbial population, as the main process drawbacks. The results of studies submitting anaerobic reactors to increasing concentrations of lipids/LCFA underlined the importance of the adsorption of LCFA onto the microbial cell membrane as limiting factor, guiding further research to found new technical approaches in order to control the biomass-LCFA adsorption dynamics. The use of inorganic adsorbents to capture LCFA prior to the anaerobic digestion process or the application of sequential low-energy ultrasonic pulses in order to control the adsorption-desorption kinetics were tested with interesting results. However, the effectiveness of these strategies was limited by the proportion of inorganic adsorbent/LCFA and the cumulative damaging effect of ultrasonic treatment over biomass, respectively. Further studies are thus required to optimize the efficiency and the applicability of these strategies. Efficient conversion of complex high-strength lipid waste to methane was proved to be possible in a novel reactor system configuration combining saponification pre-treatment and digested solids recirculation to the anaerobic digestion process, to increase solids retention time. A start-up step consisting on pulse-feeding cycles of the fatty waste prior to the semi-continuous process promoted an adapted microbial community for LCFA mineralization. The feasibility of this system configuration for solid slaughterhouse fatty waste was evidenced at lab scale reactors, reaching organic matter removal efficiencies higher than 90%. The comparison of this configuration with systems without saponification or without digested solids recirculation confirmed the synergistic effect of both strategies. The use of high throughput sequencing approach (454-pyrosequencing) to characterize the evolution of the biodiversity and the phylogenetic structure of the microbial community during the operation of the tested configurations concluded that a selection of a defined functional acidogenic population (ß-oxidizers) was induced by substrate pretreatment. Contrary, the solids recirculation resulted in an enrichment of the methanogenic biodiversity, mainly of hydrogenotrophic archaea. Based on the satisfactory results obtained with the strategies studied in the present dissertation, it is expected that lipid-rich waste valorization will be a real alternative to increase renewable energy production through anaerobic digestion process.

  • Developing tools to evaluate the environmental status of Andean basins with mining activities  Open access

     Yacoub Lopez, Cristina
    Defense's date: 2013-05-13
    Department of Chemical Engineering, Universitat Politècnica de Catalunya
    Theses

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    The water quality status of an Andean river basin was characterised and the pressures from anthropogenic activities were evaluated to enhance the available knowledge of the environment within an ecosystem in Peru. This investigation was conducted to assess the environmental status of the basin as a first step to introducing river management plans and specific water quality programmes. A continuous simulation model and an environmental monitoring program were developed, taking into account the European water framework directive (WFD) requirements. To prioritise the integrated water resources management (IWRM), an applied environmental model, the Soil and Water Assessment tool (SWAT) was used. The model was calibrated and validated for the Jequetepeque river basin using the SCE-UA algorithm and a relatively small amount of data (11 years). Five different cases of sub-basin discretisation were evaluated with and without a slope criterion. Very good hydrographs and statistics (NSE, RSR and PBIAS) were obtained for all cases. Environmental monitoring methods and tools for water quality evaluation were developed. The sources of contamination were identified and levels of contamination were quantified to evaluate pollution emissions. The degree of pollution by different substances, the associated risks, and the potential effects on aquatic life and human health were considered in the development of the tools and environmental monitoring methods. Water monitoring, sediment monitoring, and ecological monitoring, including a complementary effort to collect available data at the basin scale, were conducted in this study. The concentrations of trace elements were determined from the results of four water and sediment monitoring campaigns conducted between November 2008 and June 2010, and an ecological survey was evaluated. The results obtained from analysis of the water and sediment data indicated trace element pollution near mine sites, enabling us to quantify the impact of the mines on the Jequetepeque basin. Analysis of the water samples indicated that the most polluted water in the basin was located downstream from the Sipán SL Mine. The levels of Cr and As indicated adverse effects, whereas the levels of Al, Cd, Cu, Fe and Pb indicated significant effects on human health, mainly near the mining areas. Considering the lack of water facilities and trace element remediation in the region, special attention should be paid to regulatory policies and palliative countermeasures. Analysis of the sediment samples indicated that the most polluted sediment was located downstream from the Yanacocha Mine site and poses a significant threat to the environment in terms of Cd, Zn, Pb, and As pollution, regardless of the season. The sequential extraction analysis indicated higher mobility for Cd, Cu, Hg, Ni, and Zn. Those trace elements are released to the water column depending on the environmental conditions. The kinetics of the most prevalent trace elements in the basin were also evaluated. A diffusion model and two first-order models were used successfully to describe the kinetic extraction of Cu, Pb, and Zn. These trace elements can be significant only under extremely acidic conditions (pH=1); this should be taken into account in the potential scenario of acid mine drainage. The Ecological Status of Andean Rivers protocol was used to assess the upper part of the Jequetepeque river basin. At all the reference sites, the water quality status was very good or good. Only the sites located near mines exhibited alterations in the water quality, confirming the trends observed in the water and sediment monitoring. This protocol, which is an easy-to-use and economical qualitative tool, has proven to be very useful in assessing significant trends in ecological pollution of the basin.

    Estado de la calidad del agua fue caracterizado y las presiones de las actividades antropogénicas fueron evaluadas en una cuenca andina con el fin de promover y mejorar el conocimiento del medio ambiente dentro de un enfoque eco-sistémico en el Perú. Esta investigación fue desarrollada como un primer paso para introducir planes de gestión de programas, específicamente de calidad del agua. Para ello, un modelo de simulación continua y un programa de vigilancia ambiental se han desarrollado teniendo en cuenta las exigencias de la Directiva Marco del Agua (DMA). La dinámica de la cuenca se caracteriza por la Herramienta de Evaluación de Suelo y Agua (SWAT). Los resultados obtenidos a partir del agua y datos de sedimentos visualizan la contaminación de elementos traza cerca de las minas y cuantificar el impacto en la cuenca, principalmente para As, Cd, Cu, Pb y Zn. El estado ecológico reportado fue bueno o muy bueno para todas las muestras. Sin embargo, los puntos localizados cerca de las minas mostraron alteraciones con las mismas tendencias observadas en los monitoreos de agua y sedimento.

  • Q-00207

     Pablo Ribas, Joan de
    Participation in a competitive project

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  • Evaluation of sheep manure for in-situ acid mine drainage treatment

     Gibert Agullo, Oriol; Cortina Pallas, Jose Luis; Ayora Ibáñez, Carlos; Pablo Ribas, Joan de
    Date of publication: 2012
    Book chapter

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  • Comparison of nanofiltration membranes' performance in flat sheet and spiral wound configurations: a scale-up study

     Ribera, Gemma; Llenas Argelaguet, Laia; Martínez Lladó, Xavier; Rovira Boixaderas, Miquel; Pablo Ribas, Joan de
    Desalination and water treatment
    Date of publication: 2012-08-10
    Journal article

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    Nanofiltration (NF) membranes have been largely developed and commercialised over the past decade and are currently one of the most promising technologies for the separation of neutral and charged solutes in aqueous solutions. Sometimes NF is defined as a process between ultrafiltration and reverse osmosis; however, the separation mechanisms of this kind of membranes are not clear enough, and even today there are some questions remaining about how NF membranes work. Nowadays, there are many different types of NF membranes commercially available, so the first step before developing a new NF treatment plant is to know which one is going to be the most suitable membrane. There are two main configurations in which NF can be used: flat sheet and spiral wound module. The cross-flow module using flat sheet membranes is the simplest option to test an NF membrane but at the industrial scale, NF is basically used in the spiral wound configuration. Currently, there are no studies available regarding the difference of using both configurations. The objective of this work is to do an experimental study regarding the performance of two different NF membranes, NF270 (Dow Chemical) and ESNA 1-LF2 (Hydranautics), in two different scales, laboratory and pilot plant, using the most typical configurations in each case: flat sheet and spiral wound respectively. Using the same feed water, the operating conditions and the rejections of the membranes in both configurations will be studied in order to check if both operating scales can be comparable.

  • Pilot plant comparison study of two commercial nanofiltration membranes in a drinking water treatment plant

     Ribera, Gemma; Llenas Argelaguet, Laia; Rovira Boixaderas, Miquel; Pablo Ribas, Joan de; Martínez Lladó, Xavier
    Desalination and water treatment
    Date of publication: 2012-08-06
    Journal article

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    A wide range of commercial membranes were tested and compared at laboratory scale in order to select the most appropriate for improving the final water quality of a real drinking water treatment plant (DWTP). Most of the membranes tested showed a reduction of trihalomethanes formation potential (THMFP) higher than 90%. In this work, several NF membranes were tested at laboratory scale in order to evaluate the most suitable NF membrane to reduce THMFP. NF270 (Dow Chemical) and ESNA1LF2 (Hydranautics) were finally selected based on their permeability and inorganic salt rejection. These two membranes were tested in parallel in a pilot-scale plant. The effectiveness in THMPF removal was evident for all membranes tested. The comparison of both membranes was carried out simultaneously in a pilot plant installed in the DWTP of Manresa. In the spiral wound configuration, both membranes also showed effective separation of trihalomethanes (THM) precursors, reducing THMFP in treated water at values of approximately 90%, depending on the season.

  • Biogenic hydroxypatite (Apatite II TM) dissolution kinetics and metal removal from acid mine drainage

     Oliva Moncunill, Josep; Cama Robert, Jordi; Ayora Ibañez, Carlos; Cortina Pallas, Jose Luis; Pablo Ribas, Joan de
    Journal of hazardous materials
    Date of publication: 2012-04-30
    Journal article

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  • Kinetics of hydrogen peroxide consumption in aqueous phase at different hydrogen partial pressures

     Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Sureda Pastor, Rosa Maria; Pablo Ribas, Joan de
    Radiochimica acta
    Date of publication: 2012
    Journal article

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  • Uranium speciation in river sediments contaminated by phosphate ores

     Meca, S.; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Marti Gregorio, Vicenç; Pablo Ribas, Joan de
    Environmental chemistry letters
    Date of publication: 2012-03
    Journal article

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    Large amounts of phosphate ores with high concentrations of uranium were dumped by a phosphate plant into the Flix water reservoir in the Ebre River, Catalonia, NE Spain. These phosphate wastes have been mixed over the years with effluents from other industries as well as with the sediments of the river, resulting in a complex mixture of solid wastes and sediments. No investigations on uranium speciation in such sediments were made because of the complexity of the sediments composition as well as the relatively low uranium content. However, these studies are necessary in order to predict the release of the uranium to the river waters. Here, we studied uranium speciation in sediments from two sampling points of the Flix water reservoir and at depths from 5 to 113 cm. We used room temperature time-resolved laser fluorescence spectroscopy and a three-step sequential extraction procedure described by the Standards, Measurements, and Testing Programme of the European Union. We found that uranium was mainly present in the sediment samples as meta-autunite [Ca(UO2)2(PO4)2 10–12H2O], whose low solubility will result in a low release of uranium to the river waters. In addition, we found that some uranium was linked to sediments by forming surface complexes. We therefore made the first study of uranium speciation in the sediments of the Flix water reservoir.

  • Instant release fraction and matrix release of high burn-up UO2 spent nuclear fuel: Effect of high burn-up structure and leaching solution composition

     Serrano Purroya, D.; Clarens Blanco, Frederic; Gonzalez Robles, E.; Glatz, Jean Paul; Wegen, D.H.; Pablo Ribas, Joan de; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Martínez Esparza, A.
    Journal of nuclear materials
    Date of publication: 2012-08
    Journal article

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    wo weak points in Performance Assessment (PA) exercises regarding the alteration of Spent Nuclear Fuel (SNF) are the contribution of the so-called Instant Release Fraction (IRF) and the effect of High Burn-Up Structure (HBS). This manuscript focuses on the effect of HBS in matrix (long term) and instant release of a Pressurised Water Reactor (PWR) SNF irradiated in a commercial reactor with a mean Burn-Up (BU) of 60 GWd/tU. In order to study the HBS contribution, two samples from different radial positions have been prepared. One from the centre of the SNF, labelled CORE, and one from the periphery, enriched with HBS and labelled OUT. Static leaching experiments have been carried out with two synthetic leaching solutions: bicarbonate (BIC) and Bentonitic Granitic Groundwater (BGW), and in all cases under oxidising conditions. IRF values have been calculated from the determined Fraction of Inventory in Aqueous Phase (FIAP). In all studied cases, some radionuclides (RN): Rb, Sr and Cs, have shown higher release rates than uranium, especially at the beginning of the experiment, and have been considered as IRF. Redox sensitive RN like Mo and Tc have been found to dissolve slightly faster than uranium and further studies might be needed to confirm if they can also be considered part of the IRF. Most of the remaining studied RN, mainly actinides and lanthanides, have been found to dissolve congruently with the uranium matrix. Finally, Zr, Ru and Rh presented lower release rates than the matrix. Higher matrix release has been determined for CORE than for OUT samples showing that the formation of HBS might have a protective effect against the oxidative corrosion of the SNF. On the contrary, no significant differences have been observed between the two studied leaching solutions (BIC and BGW).

  • Modeling Biotechnological Processes under Uncertainty. Anaerobic Digestion as Case Study  Open access

     Juznic Zonta, Zivko
    Defense's date: 2012-10-26
    Department of Engineering Design, Universitat Politècnica de Catalunya
    Theses

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    En la pràctica de l’enginyeria, quan un model explícit d’un procés està disponible, es poden realitzar experiments numèrics per tal de predir el comportament futur del sistema, explicar o descriure el seu estat ocult, guiar la recopilació de dades,... Generalment, les dinàmiques del sistema són complexes i difícils d’observar amb precisió. Qualsevol aproximació de la realitat observada per mitjà d’un modelatge implica necessàriament incertesa. Per fomentar la confiança en els resultats del model, aquesta incertesa ha de ser caracteritzada i quantificada de forma explícita. En aquest projecte de tesi, particular atenció es proporciona a la incertesa associada als paràmetres del model i les seves implicacions per a l’optimització de bio-processos. Com a cas d’estudi, es considera per a la modelització la digestió anaeròbia. La producció controlada de biogàs per digestió anaeròbica s'ha trobat una activitat rendible, a més de ser una font d'energia renovable. No obstant això, els marges de millora per a aquesta tecnologia són amplis. La co-digestió anaeròbia amb dos o més materials d’entrada és una manera de fer que la biomassa de baixa producció de biogàs sigui aplicable a escala industrial. Entre els possibles co-substrats, els residus orgànics rics en lípids resulten atractius pel seu alt potencial energètic. El principal factor limitant per a aquesta estratègia és la inhibició de la digestió anaeròbica pels àcids grassos de cadena llarga. La modelització matemàtica ofereix una aproximació útil de la complexa i delicada activitat microbiologia d’aquest sistema de digestió anaeròbica. L’objectiu subjacent del projecte de tesi és millorar el procés de tractament d'aigües residuals amb l’ajuda de la modelització i l’anàlisi d’incertesa. D’acord amb aquest objectiu, es desenvolupa un entorn de simulació anomenat “planta virtual” (VP) amb la fi de aplicar-lo al modelatge de la co-digestió anaeròbia i fangs activats. A l’entorn de la VP, es proposa i testeja noves dinàmiques fonamentals del procés d’inhibició pels àcids grassos de cadena llarga i es compara diferents procediments d’inferència per l’estimació del la incertesa dels paràmetres. D’altra banda, es proposa una anàlisi de criteris múltiples en condicions d’incertesa. El mètode s’aplica a una planta industrial de co-digestió anaeròbica. Com a conclusió, l’eina de la "planta virtual" es va trobar fiable i fàcil d’usar en el modelat dels processos de tractament biològics com fangs activats i digestió anaeròbia. El model d’inhibició per àcids grassos a cadena llarga ha estat capaç de reproduir i interpretar les dades experimentals obtingudes en prèvies investigacions. No obstant això, l’estimació de la incertesa dels paràmetres i la falsificació del model d’inhibició són tasques d’investigació futura. El procediment d’inferència Bayesiana s’ha demostrat útil per enfrontar-se amb èxit al problema de l’estimació de la incertesa dels paràmetres relatius a models de la digestió anaeròbia i dels fangs activats. La anàlisi de criteris múltiples sota incertesa ha permès una considerable millora en l’eficiència i de la fiabilitat d’operació d’una planta industrial de biogàs. No obstant això, com a treball futur es fa necessari millorar el procediment d’obtenció de les entrades a l’anàlisi de criteris múltiples i disminuir la càrrega computacional requerida per aquesta anàlisi.

    In engineering practice, when an explicit model of a system is available, numerical experiments can be performed in order to predict the future behavior of the system, explain or describe its hidden state, guide data collection, etc. Typically, the dynamics of the system are complex and difficult to observe with precision. Any approximation of the observed reality within an explicit model necessary implies uncertainty, which should be characterized and quantified to build confidence over model results. Uncertainty associated with model-parameter and its implications for bio-process optimization are of main concern in this PhD work. As a bio-process case study, the anaerobic digestion is considered for modeling. The production of biogas by controlled anaerobic digestion could be a profitable activity, apart of being a renewable energy source. However, the margins to improve this technology are wide. Anaerobic co-digestion with two or more input materials is a way to make low biogas yield biomass applicable at industrial scale. Among the possible co-substrates, lipids-rich wastes are attractive for their high energetic potential. The main limiting factor for this strategy is the inhibition of anaerobic digestion by long chain fatty acids. Modeling provides a useful approximation of the complex and delicate microbiology activity of this anaerobic digestion system. The underlying goal of the PhD project is to improve biotechnological processes with the aid of modeling and uncertainty analysis. With this goal in mind, a general purpose, user-friendly, simulation environment called “virtual plant” (VP) was build and applied to anaerobic co-digestion and activated sludge modeling. Within the VP tool, new core dynamics of the long chain fatty acids (LCFA) inhibition process were proposed and tested and different inferential procedures for the estimation of parameter-uncertainty were compared. Finally, a proposed multi-criteria analysis under uncertainty and multiplicity was applied to an industrial anaerobic co-digestion biogas plant. In conclusion, the developed VP toolkit was found reliable and user-friendly when modeling activated sludge and anaerobic digestion systems. The proposed LCFA-inhibition model was able to reproduce correctly the experimental data at hand and enabled its interpretation. However, uncertainty estimation of parameters and falsification of the proposed model of LCFA-inhibition are still missing. The Bayesian procedure was proved useful when addressing the estimation of parameter uncertainty of anaerobic digestion and activated sludge models. A considerable improvement in the operation efficiency and reliability of an industrial biogas plant was possible within the proposed multi-criteria analysis. However, future work is needed to improve the procedure of elicitation of the inputs for this multi-criteria analysis and decrease its computational burden.

    En la práctica de la ingeniería, cuando un modelo explícito de un proceso está disponible, se pueden realizar experimentos numéricos para predecir el comportamiento futuro del sistema, explicar o describir su estado oculto, guiar la recopilación de datos,. . . Generalmente, las dinámicas del sistema son complejas y difíciles de observar con precisión. Cualquier aproximación de la realidad observada a través de un modelado implica necesariamente incertidumbre. Para fomentar la confianza en los resultados del modelo, esta incertidumbre debe ser caracterizada y cuantificada de forma explícita. En este proyecto de tesis, particular atención se proporciona a la incertidumbre asociada a los parámetros del modelo y sus implicaciones para la optimización de bio-procesos. Como caso de estudio, se considera para la modelización la digestión anaerobia. La producción controlada de biogás por digestión anaeróbica se ha encontrado una actividad rentable, además de ser una fuente de energía renovable. Sin embargo, los márgenes de mejora para esta tecnología son amplios. La co-digestión anaerobia con dos o más materiales de entrada es una manera de hacer que la biomasa de baja producción de biogás sea aplicable a escala industrial. Entre los posibles co-sustratos, los residuos orgánicos ricos en lípidos resultan atractivos por su alto potencial energético. El principal factor limitante para esta estrategia es la inhibición de la digestión anaeróbica por los ácidos grasos de cadena larga. La modelización matemática ofrece una aproximación útil de la compleja y delicada actividad microbiológica de este sistema de digestión anaeróbica. El objetivo subyacente del proyecto de tesis es mejorar los procesos biotecnológicos con la ayuda de la modelización y el análisis de incertidumbre. De acuerdo con este objetivo, se desarrolla un entorno de simulación llamado “planta virtual” (VP) con el fin de aplicarlo al modelado de la co-digestión anaerobia y fangos activados. En el entorno de la VP, se propone y testea nuevas dinámicas fundamentales del proceso de inhibición por ácidos grasos de cadena larga y se compara diferentes procedimientos de inferencia para la estimación del la incertidumbre de los parámetros. Por otra parte, se propone un análisis de criterios múltiples en condiciones de incertidumbre y multiplicidad de equilibrios. El método se aplica a una planta industrial de co-digestión anaeróbica. Como conclusión, la herramienta de la “planta virtual” se encontró fiable y fácil de usar en el modelado de los procesos de tratamiento biológicos como lodos activados y digestión anaerobia. El modelo de inhibición por ácidos grasos a cadena larga ha sido capaz de reproducir y ha permitido de interpretar los datos experimentales obtenidos en previas investigaciones. Sin embargo, la estimación de la incertidumbre de los parámetros y la falsificación del modelo de inhibición son tareas de investigación futura. El procedimiento de inferencia Bayesiana se ha demostrado útil para enfrentarse con éxito al problema de la estimación de la incertidumbre de los parámetros relativos a modelos de la digestión anaerobia y de los lodos activados. La propuesta análisis de criterios múltiples ha permitido una considerable mejora en la eficiencia y de la fiabilidad de operación de una planta industrial de biogás. Sin embargo, como trabajo futuro se rende necesario mejorar el procedimiento de obtención de las entradas al análisis de criterios múltiples y disminuir la carga computacional requerida por tal análisis.

  • Estudio de la viabilidad técnico-económica y ambiental de la gestión de fangos EDAR por adición de CaO para su valorización en la industria cementera  Open access

     Granados Granados, Ricardo Jose
    Defense's date: 2012-05-11
    Department of Engineering Design, Universitat Politècnica de Catalunya
    Theses

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    Urban wastewater treatment plants produce a variety of residuals during their operation, the typology of which are in function of the design of the treatment process. The problem aborded in the present thesis refers to the sludge produced as a result of the treatment. After the banning of disposal to continental and/or marine waters, established at the EU through Directive 91/271 CEE and then in Spain trough Royal Decree [RD 11/95] those sludges should be object, essentially after treatment, of controlled using or disposition. Previously to the using or disposition a previous treatment can be required, that could be organic (essentially composting with other amendments), drying or other physic-chemical treatment, between those last alkaline stabilization. Alkaline stabilization can accomplish on a single step reduction or elimination of pathogen vectors, smell elimination and a reduction in the putrefaction potential. Its base is the alteration of the physic-chemical characteristics of the environment of the sludge by addition of alkaline material. One of the processes of inertization, object of the analysis proposed in the present thesis, is the treatment realized trough addition of calcium oxide. Essentially it is a physic-chemical treatment trough which it is possible to obtain a dry product with the addition of calcium oxide (quicklime) to the urban wastewater sludge. The result of the chemical reactions and water evaporation is oriented to obtain a dry product (10% humidity) as powder and with a reduction of mass in relation to the original wastewater sludge of about 40%. The realized work have been developed over the basis of the analysis of the technical, economical and environmental feasibility of the proposed alternative, using though normalized methodology on each of the different concrete aspects that are developed. A very important part of the experimental work which validates the technology under study has been developed at pilot plant level. Additionally, the proposed management alternative of the sludge includes using the inertized sludge as a secondary raw material in Portland cement clínker production, having been developed a industrial pilot test to validate the theoretical hypothesis been established. The thesis has been developed in the core of task 6b of Project Sostaqua in program CENIT, promoted by the Centro para el Desarrollo Tecnológico e Industrial (CDTI). This had as an objective the creation of new knowledge to contribute to the development of a sustainable water life cycle. Being the sludge part of that cycle, task 6b has intended demonstrate the feasibility of the treatment with addition of alkaline agents, in this case with addition of calcium oxide. Over the basis of the obtained results it has been considered that the proposed process constitutes a feasible alternative to the management of the urban wastewater sludge. Considering that this management it is a difficult task to abroad, due to the technical difficulties implied, it should be convenient to diversify the alternatives in order to have backup treatment capacity in order to avoid the final disposition to landfill.

  • FAST INSTANT RELEASE OF SAFETY RELEVANT RADIONUCLIDES FROM SPENT NUCLEAR FUEL

     Pablo Ribas, Joan de
    Participation in a competitive project

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  • Comportamiento de actidos y productos de fisión en el medio ambiente

     Pablo Ribas, Joan de
    Participation in a competitive project

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  • SUSTAINABLE HUMAN DEVELOPMENT FOR MED COUNTRIES

     Pablo Ribas, Joan de
    Participation in a competitive project

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  • Chromium recovery from exhausted baths generated in plating processes and its reuse in the tanning industry

     Torras Grane, Josep; Buj Corral, Irene; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de
    Journal of hazardous materials
    Date of publication: 2012-03-30
    Journal article

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  • Removal of cadmium, copper, nickel, cobalt and mercury from water by Apatite IITM: column experiments

     Oliva Moncunill, Josep; Pablo Ribas, Joan de; Cortina Pallas, Jose Luis; Cama Robert, Jordi; Ayora Ibañez, Carlos
    Journal of hazardous materials
    Date of publication: 2011-10-30
    Journal article

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  • Solution-diffusion-film model for the description of pressure-driven trans-membrane transfer of electrolyte mixtures: One dominant salt and trace ions

     Yaroshchuk, Andriy; Martínez Lladó, Xavier; Llenas Argelaguet, Laia; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de
    Journal of membrane science
    Date of publication: 2011-02-15
    Journal article

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  • Nanofiltration as pretreatment for scale prevention in seawater reverse osmosis desalination

     Llenas Argelaguet, Laia; Yaroshchuk, Andriy; Rovira Boixaderas, Miguel Arcangel; Martínez Lladó, Xavier; Pablo Ribas, Joan de
    Desalination and water treatment
    Date of publication: 2011-12
    Journal article

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  • In-situ remediation of acid mine drainage using a permeable reactive barrier in Aznalcóllar (Sw Spain)

     Gibert Agullo, Oriol; Rötting, Tobias; Cortina Pallas, Jose Luis; Pablo Ribas, Joan de; Carrera, J.; Ayora Ibañez, Carlos; Bolzicco, J,
    Journal of hazardous materials
    Date of publication: 2011-07-15
    Journal article

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  • Valorization of brines in the chlor-alkali industry. Integration of precipitation and membrane processes

     Casas Garriga, Sandra
    Defense's date: 2011-12-15
    Department of Engineering Design, Universitat Politècnica de Catalunya
    Theses

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  • Study of Radionuclide Release in commercials UO2 Spent Nuclear Fuels

     Gonzalez-robles Corrales, Ernesto
    Defense's date: 2011-11-22
    Department of Chemical Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Avaluació i caracterització d'una apatita biogènica pel tractament in situ d'aigües subterrànies i sòls contaminats per activitats mineres

     Oliva Moncunill, Josep
    Defense's date: 2011-04-27
    Department of Mining Engineering and Natural Resources, Universitat Politècnica de Catalunya
    Theses

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    Determination of the equilibrium formation constants of two U(VI)-peroxide complexes at alkaline pH  Open access

     Meca, S.; Martinez Torrents, Albert; Marti Gregorio, Vicenç; Gimenez Izquierdo, Francisco Javier; Casas Pons, Ignasi; Pablo Ribas, Joan de
    Dalton transactions
    Date of publication: 2011
    Journal article

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    The formation of uranyl-peroxide complexes was studied at alkaline media by using UV-Visible spectrophotometry and the STAR code. Two different complexes were found at a H2O2/U(VI) ratio lower than 2. A graphical method was used in order to obtain the formation constants of such complexes and the STAR program was used to refine the formation constants values because of its capacity to treat multiwavelength absorbance data and refining equilibrium constants. The values obtained for the two complexes identified [...] At hydrogen peroxide concentrations higher than 10-5 mol dm-3, and in the absence of carbonate, the UO2(O2)2(OH)2 4- complex is predominant in solution, indicating the significant peroxide affinity of peroxide ions for uranium and the strong complexes of uranium(VI) with peroxide.

  • Effects of ionizing radiation and temperature on uranyl silicates: Soddyite (UO2)2(SiO4)(H2O)2 and uranophane Ca(UO2)2(SiO3OH)2 3.5H2O

     Sureda Pastor, Rosa Maria; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Quiñones Ruiz, Jose Miguel; Zhang, Jun-Ying; Ewing, R.C.
    Environmental science and technology
    Date of publication: 2011-03-15
    Journal article

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  • Semi-dynamic leaching tests of nickel containing wastes stabilized/solidified with magnesium potassium phosphate cements

     Torras Grane, Josep; Buj Corral, Irene; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de
    Journal of hazardous materials
    Date of publication: 2011-02-28
    Journal article

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    Herein is presented a study on the long-term leaching behaviour of nickel containing wastes stabilized/solidified with magnesium potassium phosphate cements. Two different semi-dynamic leaching tests were carried out on monolithic materials: ANS16.1 test with liquid-to-solid ratio (L/S) of 10dm3 kg−1 and increasing renewal times, and ASTM C1308 test with liquid-to-solid ratio (L/S) of 100dm3 kg−1 and constant renewal time of 1 day. ASTM C1308 provides a lower degree of saturation of the leachant with respect to the leached material. The effectiveness of magnesium potassium phosphate cements for the inertization of nickel was proved. XRD analyses showed the presence of bobierrite on the monolith’s surface after the leaching test, which had not been detected prior to the leaching test. In addition, the calculated cumulative release of the main components of the stabilization matrix (Mg2+, total P and K+)was represented versus time in logarithmic scale and it was determined if the leaching mechanism corresponds to diffusion. Potassium is released by diffusion, while total phosphorous and magnesium show dissolution. Magnesium release in ANS 16.1 is slowed down because of saturation of the leachant. Experimental results demonstrate the importance of L/S ratio and renewal times in semi-dynamic leaching tests.

  • Transport of strontium through a Ca-bentonite (Almeria, Spain) and comparison with MX-80 Na-bentonite: experimental and modelling

     Valderrama Angel, Cesar Alberto; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Martínez Martínez, María R.
    Water, air and soil pollution
    Date of publication: 2011-06
    Journal article

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  • Sorption and mobility of Sb(V) in calcareous soils of Catalonia (NE Spain): Batch and column experiments

     Martínez Lladó, Xavier; Valderrama Angel, Cesar Alberto; Rovira Boixaderas, Miguel Arcangel; Marti Gregorio, Vicenç; Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de
    Geoderma
    Date of publication: 2011-01-15
    Journal article

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    The sorption of Sb(V) onto natural calcareous soils was studied in batch and column experiments as a function of physicochemical properties of the soil, namely: organic matter, the active fraction of Fe and Al and the pH of the soils. Batch experiments were performed in order to determine the sorption capacity and the kinetic rate of the sorption. Freundlich isotherm described properly the equilibrium experimental data and the kinetic results show that the sorption was very slow in all the soils studied (equilibrium after 7 days) when compared with literature data for Sb(V) sorption onto soils with higher iron content. Column experiments were carried out in order to determine the mobility of Sb(V) in the soils. The Thomas model can describe partially the breakthrough curves obtained for the Sb(V) sorption on the soils. The fitting of the model to the experimental data would indicate that transport and kinetic parameters also affected the dynamic sorption behavior. The experimental breakthrough curves can be properly described by the convective–dispersive equation (CDE) by using the CXTFIT code, and the parameters obtained by the model were in concordance to the sorption capacity reported in the column experiments. This study indicates that sorption of Sb(V) onto the soils is mainly affected in batch experiments by their ‘active’ Fe and Al content; while in column experiments organic matter content appeared as an important parameter. Desorption experiments resulted in a metalloid recovery above 90%, which indicates a fast and effective method to recover Sb(V) from calcareous soils and has implications for its geochemical behavior (vertical mobility in soil profiles) as a result of its relatively low Sb retention.

  • Statistical testing based methodology for the analysis of soil pollution evidence

     Marti Gregorio, Vicenç; Pablo Ribas, Joan de; Gibert Agullo, Oriol; Gimenez Izquierdo, Francisco Javier; Martínez Lladó, Xavier; De Fays, Isolda
    International UFZ-Deltares/TNO Conference, on Management of Soil, Groundwater and Sediments
    Presentation's date: 2010-09-22
    Presentation of work at congresses

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  • Assessment of heterotrophic and autotrophic denitrification in aquifers by using batch tests

     Calderer, M.; Marti Gregorio, Vicenç; Pablo Ribas, Joan de; Rovira Boixaderas, Miguel Arcangel; Gibert Agullo, Oriol; Gimenez Izquierdo, Francisco Javier
    International UFZ-Deltares/TNO Conference, on Management of Soil, Groundwater and Sediments
    Presentation's date: 2010-09-22
    Presentation of work at congresses

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  • Generic values for groundwater restoration in aquifers contaminated by point sources

     Orejudo, Emili; Espínola, M. R.; Rovira, María; Marti Gregorio, Vicenç; Pablo Ribas, Joan de; Rovira Boixaderas, Miguel Arcangel
    International UFZ-Deltares/TNO Conference, on Management of Soil, Groundwater and Sediments
    Presentation's date: 2010-09-22
    Presentation of work at congresses

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  • Leaching behaviour of magnesium phosphate cements containing high quantities of heavy metals

     Buj Corral, Irene; Torras Grane, Josep; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de
    Journal of hazardous materials
    Date of publication: 2010-03-15
    Journal article

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    Stabilization/solidification (S/S) is one of the most employed techniques for treating liquid wastes containing heavy metals. Magnesium potassium phosphate cements have been used in recent years as stabilizing agents with positive results. However, little information is available about the retention of the metals by magnesium potassium phosphate cements matrices with the exception of the results of compliance tests. In this work, several pastes were prepared by reaction between low grade MgO and KH2PO4 in the presence of different heavy metal nitrate solutions (containing Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) or Zn(II)). In all cases, the initial metal content of the dissolution was 25 g dm−3 and the oxide–phosphate ratio of the pastes was (50:50) in weight. Four different leaching tests were conducted on magnesium potassium phosphate cement pastes: simple batch test (EN 12457-2), equilibrium leaching test, availability test (NEN 7371) and acid neutralization capacity test (ANC). The metal leachate concentration was determined by means of ICP-MS. The stabilization of metals was successful in all cases, although the immobilizing system shows a better behaviour for Pb(II) and Cr(III) under acidic or neutral conditions.

  • Broadening of neutral solute band in electroosmotic flow through submicron channel with longitudinal non-uniformity of zeta potential

     Zholkovskij, Emilij K.; Yaroshchuk, Andriy; Masliyah, Jacob H.; Pablo Ribas, Joan de
    Colloids and surfaces A: physicochemical and engineering aspects
    Date of publication: 2010-02
    Journal article

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    The present study is concerned with broadening of neutral solute band in electrically driven flow through a straight channel with longitudinally varying zeta potential. The present analysis takes into account effects that are important for submicron channels, namely, variation of the excess conductivity in the diffuse part of the electric Double Layer and the non-uniformity of the velocity profile within the Double Layer. Initially, the combined, electroosmotic and pressure driven flow through a straight channel is addressed for the case of longitudinal variation of zeta potential. Using the obtained distribution of the hydrodynamic velocity, the plate height for a non-electrolyte neutral solute is interrelated with the longitudinal distribution of the electrokinetic potential. Several examples of cross-section geometry and electrolyte composition are discussed.

  • Modelling enhanced groundwater denitrification in batch micrococosm tests

     Calderer, M.; Jubany, Irene; Pérez Magrané, Ramon; Marti Gregorio, Vicenç; Pablo Ribas, Joan de
    Chemical engineering journal
    Date of publication: 2010
    Journal article

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  • In situ removal of arsenic from groundwater by using permeable reactive barriers of organic matter/limestone/zero-valent iron mixtures

     Gibert Agullo, Oriol; Pablo Ribas, Joan de; Cortina Pallas, Jose Luis; Ayora Ibáñez, Carlos
    Environmental geochemistry and health
    Date of publication: 2010-08
    Journal article

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    Abstract In this study, two mixtures of municipal compost, limestone and, optionally, zero-valent iron were assessed in two column experiments on acid mine treatment. The effluent solution was systematically analysed throughout the experiment and precipitates from both columns were withdrawn for scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry analysis and, from the column containing zero-valent iron, solid digestion and sequential extraction analysis. The results showed that waters were cleaned of arsenic, metals and acidity, but chemical and morphological analysis suggested that metal removal was not due predominantly to biogenic sulphide generation but to pH increase, i.e. metal (oxy)hydroxide and carbonate precipitation. Retained arsenic and metal removal were clearly associated to co-precipitation with and/or sorption on iron and aluminum (oxy)hydroxides. An improvement on the arsenic removal efficiency was achieved when the filling mixture contained zero-valent iron. Values of arsenic concentrations were then always below 10 lg/L.

  • Access to the full text
    The use of apatite II (TM) to remove divalent metal ions zinc (II), lead (II), manganese (II) and iron (II) from water in passive treatment systems: column experiments  Open access

     Oliva Moncunill, Josep; Pablo Ribas, Joan de; Cortina Pallas, Jose Luis; Cama Robert, Jordi; Ayora Ibáñez, Carlos
    Journal of hazardous materials
    Date of publication: 2010-12-15
    Journal article

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    Postprint (author’s final draft)

  • Study of Denitrification and Reductive Dechlorination Processes Applied to Groundwater Bioremediation  Open access

     Calderer Perich, Montserrat
    Defense's date: 2010-06-23
    Department of Chemical Engineering, Universitat Politècnica de Catalunya
    Theses

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    La present tesi es basa en l'estudi dels processos de bioremediació com a tecnologies de descontaminació d'aqüífers.Concretament, es pretén estudiar la desnitrificació i la decloració reductiva com a tecnologies de bioremediació per eliminar, respectivament, els nitrats i els hidrocarburs alifàtics clorats (o CAHs, de chlorinated aliphatic hydrocarbons) de les aigües subterrànies contaminades. A més, es pretén aplicar tecnologies avançades que permetin millorar en el coneixement d'aquests processos.L'aqüífer associat a la riera d'Argentona, situat a Argentona (Espanya), ha estat la zona d'estudi per tal d'investigar el procés de desnitrificació. En primer lloc, s'han dut a terme experiments en batch amb aigua subterrània i sòl subsuperficial del mencionat aqüífer. A partir d'aquests primers estudis, s'ha observat la baixa capacitat de l'aqüífer per eliminar els nitrats de manera natural, però alhora s'ha vist la viabilitat d'aplicar un procés de bioremediació com és l'addició de matèria orgànica. Paral·lelament, s'ha estudiat la influència de diferents factors com ara la presència d'oxigen i la tipologia de donador d'electrons sobre el procés de desnitrificació.Posteriorment, s'ha desenvolupat un model matemàtic per descriure el consum d'oxigen, de nitrats i de matèria orgànica per part de la població microbiana facultativa i heterotròfica present en el material d'aqüífer. Alguns paràmetres del model han estat calibrats i s'ha estudiat la qualitat d'aquests paràmetres. El model desenvolupat constitueix una primera aproximació per tal d'obtenir un model de desnitrificació in situ.Per tal d'avançar en l'estudi del procés de desnitrificació en condicions naturals, s'han realitzat experiments en dinàmic simulant el flux d'aigua subterrània a través de l'aqüífer. L'eficiència d'injectar matèria orgànica en aquestes condicions s'ha demostrat.Paral·lelament, s'han estudiat els efectes hidrodinàmics de l'aplicació de la bioremediació i, els resultats han demostrat la importància de dissenyar acuradament les tecnologies de bioremediació a escala de camp. Per altra banda, s'ha descrit la desnitrificació en condicions dinàmiques integrant en un model matemàtic les reaccions bioquímiques i els processos de transport que tenen lloc a la columna experimental.Finalment, s'han aplicat les noves tecnologies de biologia molecular per entendre els efectes de l'aplicació d'un procés de bioremediació a nivell microbià. Per una banda, l'aplicació de la tècnica de la reacció en cadena de la polimerasa a temps real (o real-time PCR, de real-time polymerase chain reaction) ha demostrat el creixement de la població microbiana i, concretament, de la població desnitrificant en el material d'aqüífer estimulat. Per altra banda, l'electroforesi en gel de gradient desnaturalitzant (o DGGE, de denaturing gradient gel electrophoresis) ha permès investigar els canvis en la població microbiana indígena del material d'aqüífer a causa de l'estimulació amb matèria orgànica.Amb l'objectiu d'avançar en el coneixement dels processos de bioremediació en aigües subterrànies, s'ha estudiat també la decloració reductiva de CAHs. En aquest cas, s'han aplicat metodologies experimentals destinades a l'estudi de la posible aplicació d'una barrera reactiva permeable per eliminar una ploma que conté majoritàriament cis-1,2-dicloroetilè i clorur de vinil, i que flueix cap al riu Zenne, prop de la ciutat de Brussel·les (Bèlgica).L'estudi ha inclòs experiments en batch per tal d'investigar el potencial degradatiu del material d'aqüífer i dels propis sediments del riu Zenne. Així mateix, també s'han dut a terme experiments en columna que simulaven el flux d'aigua subterrània a través dels sediments del riu o del material d'aqüífer. Els resultats han demostrat el gran potencial degradatiu dels sediments, que a la llarga es podrien potenciar com a biobarrera natural del sistema per tal de prevenir que les aigües contaminades arribin a l'aigua superficial del riu Zenne.

    This thesis is based on the study of bioremediation processes as reliable technologies to remove contaminants from groundwater.Specifically, it is aimed to study denitrification and reductive dechlorination as bioremediation technologies to remove nitrates and chlorinated aliphatic hydrocarbons (CAHs), respectively, from polluted groundwater. In addition, it is aimed to apply advanced technologies which allow improving on the knowledge of these processes.The aquifer associated to the Stream Argentona, located in Argentona, Catalunya (Spain), was selected as study site to investigate the denitrification process. In the first part, microcosm experiments containing groundwater and subsoil from the aquifer were performed. From these first studies it was observed the low capacity of the aquifer to eliminate nitrates under natural conditions, but, at the same time, it was noted the feasibility of applying a bioremediation process such as the addition of organic matter. In addition, the influence of different factors such as the presence of oxygen and the type of electron donor on the denitrification process was studied.Afterwards, a mathematical model was developed to explain the microbiological processes that occur when stimulating the aquifer material with an organic carbon source. The model could successfully explain the consumption of oxygen, nitrates and organic matter by the indigenous facultative heterotrophic microbial population from aquifer. Some parameters of the model were calibrated from experimental data and the quality of these parameters was investigated. The developed model constitutes a first approach in order to have reliable models for in situ denitrification.In order to advance in the study of the denitrification process in natural conditions, dynamic experiments were carried out simulating the groundwater flow through the aquifer. The efficiency of injecting organic matter under these conditions was demonstrated. At the same time, hydrodynamic effects of the process were observed, indicating the importance to design properly bioremediation technologies before its application in field-scale. Furthermore, an integrated model coupling the biochemical reactions and the transport processes inside the column was developed and applied to describe denitrification under dynamic conditions.Finally, molecular microbiological techniques were applied to investigate microbial changes due to the application of enhanced denitrification. On the one hand, real-time polymerase chain reaction (real-time PCR) assays revealed the growth of microbial population, specially of denitrifying bacteria in aquifer material stimulated with an organic carbon source. On the other hand, the denaturing gradient gel electrophoresis (DGGE) method allowed to investigate changes in the indigenous microbial community due to the amendment with organic matter.In order to advance in the knowledge of bioremediation processes in groundwater, reductive dechlorination of CAHs in groundwater was studied. In this case, experiments at laboratory scale were applied, aimed to study the possible application of a permeable reactive barrier (PRB) to eliminate a CAH-contaminated plume, containing basically cis-1,2-dichloroethene and vinyl chloride, which flows to the River Zenne near Brussels, Belgium.The study included batch experiments in order to investigate the degradation potential in aquifer and sediments of the River Zenne, as well as column experiments which simulated the groundwater flow through the sediments of the river or the aquifer material. The results demonstrated the high degradation potential of the sediments, which in the long term could be enhanced to act as a natural biobarrier of the system in order to prevent groundwater contaminants from arriving at the surface water of the River Zenne.

  • Sorption of strontium on uranyl peroxide: implications for a high-level nuclear waste repository

     Sureda Pastor, Rosa Maria; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Martínez Lladó, Xavier
    Journal of hazardous materials
    Date of publication: 2010-09-15
    Journal article

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    Strontium-90 is considered the most important radioactive isotope in the environment and one of the most frequently occurring radionuclides in groundwaters at nuclear facilities. The uranyl peroxide studtite (UO2O2 center dot 4H(2)O) has been observed to be formed in spent nuclear fuel leaching experiments and seems to have a relatively high sorption capacity for some radionuclides. In this work, the sorption of strontium onto studtite is studied as a function of time. strontium concentration in solution and pH. The main results obtained are (a) sorption is relatively fast although slower than for cesium; (b) strontium seems to be sorbed via a monolayer coverage of the studtite surface, (c) sorption has a strong dependence on ionic strength, is negligible at acidic pH, and increases at neutral to alkaline pH (almost 100% of the strontium in solution is sorbed above pH 10). These results point to uranium secondary solid phase formation on the spent nuclear fuel as an important mechanism for strontium retention in a high-level nuclear waste repository (HLNW). (C) 2010 Elsevier B.V. All rights reserved.

  • Reactive transport of arsenic(III) and arsenic(V) on natural hematite: Experimental and modeling

     Gimenez Izquierdo, Francisco Javier; Pablo Ribas, Joan de; Martínez Martínez, María R.; Rovira Boixaderas, Miguel Arcangel; Valderrama Angel, Cesar Alberto
    Journal of colloid and interface science
    Date of publication: 2010-08-01
    Journal article

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  • Cesium sorption on studtite (UO2O2·4H2O)

     Gimenez Izquierdo, Francisco Javier; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de; Casas Pons, Ignasi; Sureda Pastor, Rosa Maria; Martínez Lladó, Xavier; Martínez Esparza, A.
    Radiochimica acta
    Date of publication: 2010
    Journal article

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  • Denitrification in presence of acetate and glucose for bioremediation of nitrate-contaminated groundwater

     Calderer, M.; Gibert Agullo, Oriol; Marti Gregorio, Vicenç; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de; Jordana, S.; Guimera, J; Bruno Salgot, Jorge
    Environmental technology
    Date of publication: 2010
    Journal article

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  • Effect of temperature on studtite stability: Thermogravimetry and differential scanning calorimetry investigations

     Rey, A; Casas Pons, Ignasi; Gimenez Izquierdo, Francisco Javier; Quiñones Ruiz, Jose Miguel; Pablo Ribas, Joan de
    Journal of nuclear materials
    Date of publication: 2009-03
    Journal article

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  • Stability of uranium (VI) peroxide hydrates under ionizing radiation

     Rey, A; Utsunomiya, S; Gimenez, J; Casas Pons, Ignasi; Pablo Ribas, Joan de; Ewing, Rc
    American mineralogist
    Date of publication: 2009-03
    Journal article

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  • Thorium sorption onto magnetite and ferrihydrite in acidic conditions

     Rojo, I; Seco, F; Rovira Boixaderas, Miguel Arcangel; Giménez, J; Cervantes Torre-Marín, Gemma; Marti Gregorio, Vicenç; Pablo Ribas, Joan de
    Journal of nuclear materials
    Date of publication: 2009-03
    Journal article

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  • Sorption of Th(IV) onto Iron Corrosion Products: EXAFS Study

     Seco, F; Hennig, C; Pablo Ribas, Joan de; Rovira Boixaderas, Miguel Arcangel; Rojo, I; Marti Gregorio, Vicenç; Gimenez, J; Duro, L; Grive, M; BRUNO, J
    Environmental science and technology
    Date of publication: 2009-04
    Journal article

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  • Effect of heavy metals and water content on the strength of magnesium phosphate cements.

     Buj Corral, Irene; Torras Grane, Josep; Casellas Padro, Daniel; Rovira Boixaderas, Miguel Arcangel; Pablo Ribas, Joan de
    Journal of hazardous materials
    Date of publication: 2009-10
    Journal article

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