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Ollivier P.,Bureau de Recherches Geologiques et Minieres | Ollivier P.,CNRS Earth Sciences Institute of Orleans | Surdyk N.,Bureau de Recherches Geologiques et Minieres | Azaroual M.,Bureau de Recherches Geologiques et Minieres | And 4 more authors.
Chemical Geology | Year: 2013

The spatial and temporal evolution of the physical properties and chemical composition of water and soil during the infiltration of treated wastewater through a reactive soil column at the pilot scale (25m3) were investigated for 18months. Major and trace elements, and organic carbon were measured monthly in treated wastewater, output water and pore water. O2, CO2, CH4, N2O, N2, H2S and H2 were measured occasionally in soil air. Geochemical processes occurring in the soil changed rapidly over the study period. Nitrification was effective in the top 1.5m of soil during the first 8months. Thereafter, the organic carbon load from treated wastewater and the treated wastewater left above the infiltration surface due to clogging (organic matter accumulation and precipitation of carbonates) created anaerobic conditions that led to denitrification and reductive dissolution of Mn oxides in the soil. The latter led to the release of both Mn (exceeding the WHO drinking water limit by a factor of up to 2) and Ni that was strongly associated with the Mn oxides. Forty-five percent of the Ni that had accumulated in the soil during the first year was released. Dissolved element concentrations were non-uniform because of the spatial and temporal distribution of redox reactions in the soil due to the heterogeneous distribution of organic matter and/or non-uniform flow (water saturation, residence time). The soil was very effective in removing phosphate, Fe, and Li, and removing/degrading organic carbon and NH4. In contrast, Ba, NO3 and, to a lesser extent, Ca were exported. Removal rates were moderate for As and total nitrogen, and low for K, Na, Ni and Mn. However, removal rates of nitrogen species (NH4, NO3), total nitrogen, Mn, Fe, Ni and As were strongly dependent on redox conditions which varied during the experiment. The evolution of geochemical processes occurring in the soil column therefore has significant implications on the quality of water moving from the soil to groundwater and provides key knowledge for the management of groundwater under artificial recharge. © 2013 Elsevier B.V. Source


Guionet A.,CNRS Institute of Pharmacology and Structural Biology | Guionet A.,Toulouse 1 University Capitole | David F.,VERI | Zaepffel C.,ONERA | And 8 more authors.
Bioelectrochemistry | Year: 2015

One of the different ways to eradicate microorganisms, and particularly bacteria that might have an impact on health consists in the delivery of pulsed electric fields (PEFs). The technologies of millisecond (ms) or microsecond (μs) PEF are still well known and used for instance in the process of fruit juice sterilization. However, this concept is costly in terms of delivered energy which might be too expensive for some other industrial processes.Nanosecond pulsed electric fields (nsPEFs) might be an alternative at least for lower energetic cost. However, only few insights were available and stipulate a gain in cost and in efficiency as well. Using Escherichia coli, the impact of frequency and low rate on eradication and energy consumption by msPEF, μsPEF and nsPEF have been studied and compared. While a 1 log10 was reached with an energy cost of 100 and 158kJ/L with micro- and millisecond PEFs respectively, nsPEF reached the reduction for similar energy consumption. The best condition was obtained for a 1 log10 deactivation in 0.5h, for energy consumption of 143kJ/L corresponding to 0.04W·h when the field was around 100kV/cm. Improvement can also be expected by producing a generator capable to increase the electric field. © 2014 Elsevier B.V. Source


Gal F.,Bureau de Recherches Geologiques et Minieres | Lions J.,Bureau de Recherches Geologiques et Minieres | Pokryszka Z.,INERIS | Gombert P.,INERIS | And 4 more authors.
Energy Procedia | Year: 2014

Geological storage of CO2 in deep saline aquifers is one of the options considered for the mitigation of CO2 emissions into the atmosphere. A deep geological CO2 storage is not expected to leak but potential leakage monitoring is required by legislation, as e.g. the EU Directive relative to Geological Storage of CO2. To ensure that the storage will be permanent and safe for the environment and human health, the legislation require that the CCS operators monitor the injection, the storage complex and if needed the environment to detect any CO2 leakage and its hazardous effects on the environment. Various monitoring methods are available for the monitoring of CO2 storage sites and the environment as listed by the IEA-GHG and the monitoring selection tool. Geophysical based methods have a greater area of investigation but may suffer from insufficient sensitivities to detect small leakages. At the opposite, geochemical monitoring methods may have insufficient investigation area but may be able to detect more subtle changes even if monitoring in deep environments is not straightforward. Leakage detection is not yet well constrained and research efforts and tests are required to gain confidence into monitoring strategies. In the framework of the CIPRES project, funded by the French Research Agency, a shallow CO2 release experiment has been performed in October 2013 in a chalk aquifer from the Paris basin. The Catenoy site has been characterised since March 2013 through several wells set on a straight line oriented along the local flow (see Gombert et al., this conference). Such an experiment is designed to gain confidence in leakage detection in subsurface environments by understanding processes and principles governing seepage occurrence. Contrary to other experiments such as ZERT or CO2 FieldLab ones, where gaseous CO2 was injected directly in the water, the injection was done with water saturated with CO2 at atmospheric pressure. 10 m3 of water were pumped from the aquifer, then saturated with 20 kg of food-grade CO2 and injected during 40 hours between 12 and 25 m depth. Daily monitoring of soil gases and water was performed during injection and post-injection phases (2 weeks duration) in the area previously delimited by a tracer test. The aim is to determine if geochemical methods are accurate enough to allow detecting small release in shallow environments. If successful, such an experiment can help to gain confidence in leakage detection. As expected, no change was noticed in the unsaturated zone. The shape of gas concentrations distribution at the surface (CO2, O2, N2, 4He, 222Rn) observed during the injection is strictly similar to the repartition of gas species observed since March 2013. The main process observed is respiration and no change linked to the injection was highlighted, only seasonal effects. Slight changes were observed in the saturated zone. The water was collected at 15 m deep excepted for one stratified borehole where water was sampled at 15 and 18 m. The pH of the injected water was lower (mean value: 5.3±0.1) than the initial pH of the aquifer (7.1-7.2) due to CO2 dissolution. Only two monitoring boreholes set 10 m and 20 m downstream from the injection well may be considered as influenced by the experiment. A probable enrichment in HCO3linked to interaction of the CO2 saturated water with chalk was noticed, with an enrichment close to +8 to +10% of the initial value. For one borehole the pH value remained nearly stable in relation with pH buffering and in the other borehole a slight decrease was observed (-0.1 to -0.15 pH unit). However this decrease is significant as it is above the instrumental uncertainty of the electrodes. In addition, a slight increase of the electrical conductivity was noticed but it did not exceed +6% compared to baseline data. Such slight changes in the physico-chemical parameters are related to small variations in dissolved elements. Apart from HCO3, the other major ion affected by CO2-water rock-interaction is Ca as the aquifer is mainly composed by calcite. Concentrations increases by +8 to +9% whose amplitude is in agreement with the increase of HCO3. Trace elements were also little affected, the main change concerned Sr (+8 to +10% increase). Modifications occurring during this CO2 release experiment have small amplitude as expected but these results highlight that geochemical methods are able to detect small leakages. Consequently, effects were noticed only during a short period of time. It is not possible to determine if all the injected CO2 has migrated downwards in the direction of flow or if partial lateral migration has occurred, but post-injection monitoring and boreholes logging 12 days after the stop of injection did not reveal any discrepancy in the water columns. On the other hand, the magnitude of the pH change is consistent with the behaviour of the co-injected tracer (dilution ratio ∼30). In the perspective of getting more information on the remobilisation of trace metal elements, a push-pull test will be performed in 2014 on the basis of the learning of this first experiment. © 2014 The Authors. Published by Elsevier Ltd. Source


Guionet A.,CNRS Institute of Pharmacology and Structural Biology | Guionet A.,Toulouse 1 University Capitole | David F.,VERI | Zaepffel C.,ONERA | And 8 more authors.
Bioelectrochemistry | Year: 2014

One of the different ways to eradicate microorganisms, and particularly bacteria that might have an impact on health consists in the delivery of pulsed electric fields (PEFs). The technologies of millisecond (ms) or microsecond (μs) PEF are still well known and used for instance in the process of fruit juice sterilization. However, this concept is costly in terms of delivered energy which might be too expensive for some other industrial processes.Nanosecond pulsed electric fields (nsPEFs) might be an alternative at least for lower energetic cost. However, only few insights were available and stipulate a gain in cost and in efficiency as well. Using Escherichia coli, the impact of frequency and low rate on eradication and energy consumption by msPEF, μsPEF and nsPEF have been studied and compared. While a 1 log10 was reached with an energy cost of 100 and 158kJ/L with micro- and millisecond PEFs respectively, nsPEF reached the reduction for similar energy consumption. The best condition was obtained for a 1 log10 deactivation in 0.5h, for energy consumption of 143kJ/L corresponding to 0.04W·h when the field was around 100kV/cm. Improvement can also be expected by producing a generator capable to increase the electric field. © 2014 Elsevier B.V. Source


Teixeira G.,VERI | Van De Steene L.,CIRAD - Agricultural Research for Development | Salvador S.,Albi-Carmaux School of Engineering | Gelix F.,VERI | And 2 more authors.
Chemical Engineering Transactions | Year: 2014

The current paper presents a study combining experimentation and modelling of char gasification in a continuous fixed bed reactor. The char bed gasification was experimentally characterized using the Continuous Fixed Bed reactor (CFiB) at CIRAD (Montpellier, France). This reactor replicates the gasification zone taking place in the co-current, multi-stage gasification technology. It is instrumented to specifically allow the measurement of thermal and chemical profiles: measurements of temperature, pressure, and gas composition are performed every 10 cm along the bed. We also investigate the char bed compaction during gasification. For this purpose, a char bed sampling was carried out to measure char bed density and particle velocities along the char bed. A model of wood char gasification in a continuous fixed bed reactor was thus developed using COMSOL software. It couples heat and mass transfer phenomena with heterogeneous and homogenous chemical reactions taking place inside the bed. In particular, this model considers char bed compaction to predict evolution of char bed density and velocity. As an innovative approach, three simple functions to calculate char particle conversion rate of the heterogeneous reactions were proposed. Copyright © 2014,AIDIC Servizi S.r.l. Source

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