Colmatage microbien des forages et circulation de l'eau - Résultats d'un « colmatomètre » expérimental

Un modèle physique est constitué de quatre éprouvettes de sable percolées à des vitesses de flux différentes par L'eau d'un forage colmaté.On a pu ainsi obtenir, en quelques semaines, un colmatage différentiel de deux éprouvettes percolées à des vitesses supérieures à 1 cm/s, et confirmer les hypothèses émises sur l'influence de La vitesse réelle des filets liquides dans L'apparition du colmatage, et sur ta nature bactérienne du processus colmatant.Ce modèle constitue un véritable "colmatomètre" qui a donné lieu au dépôt d'un brevet (BOURGUET et al., 1985). Avant La réalisation d'un champ captant nouveau, L'emploi d'un tel colmatomètre devrait permettre d'apprécier les risques de colmatage spécifiques au site, et de définir Les normes de crépinage et d'exploitation permettant de Les éviter, ou du moins de les minimiser.INTRODUCTIONA study on 300 wells drilled in the Ypresian aquifer, over 60 % of which were clogged, revealed that there were significant statistic relationships between the frequency of ctogging, the high velocities of the water close to the well screens and the presence of hydrogen sulfide in the water; the latter means the existence of sulfato-reducing bacterial activity.The experimental model described here was designed to check the effect of the velocity of the water in the aquifer on the creation of clogging, as well as its relationship with the development of the bacterial population induced by a sufficient nutrient flow rate.This model, comprising sterilized sand, through wich water from a clogged well percolated, was set up prior to a model which will soon be built, consisting of cores of Ypresian sand containing its own microorganisms.APPARATUS AND METHODSFour stainless-steel tubes (length 14 cm, inner diameter 26 mm) were filled with sterilized siliceous sand, the initial porosity of which was 35 %. The particle size distribution (40 to 140 µm) and the permeability were similar to those of the Ypresian sand. Tube seeding was carried out for a week by percolation with water from a clogged well; no clogging in the tubes was observed. This water was then percotated simultaneously through the tubes (figure 2) for 58 days at rates, maintained by weekly corrections, close to 1, 3, 12 and 30 mm/s respectively (figure 3).The microbiological analyses consisted in : direct numeration of bacterial bodies by epifluorescence microscopy, indirect numeration by counting revivifiable heterotrophic aerobic bacteria after 15 days incubation within a medium chosen to be the least selective possible and, lastly, the numeration of both permanent and casual anaerobia, as well as sulfatoreducing bacteria following Hungate's method.HYDRODYNAMIC RESULTS (figure 4)The reduction of permeability, which results from clogging, after 58 days of percolation was the following :- tube nb 1          0 % for an average percolation rate of 0.8 mm/s,- tube nb 2         2 % for an average percolation rate of 2.5 mm/s,- tube nb 3         29,5 % for an average percolation rate of 11.5 mm/s,- tube nb 4         59 % for an average percolation rate of 30.8 mm/s.Tubes nb 1, 2 and 4 were destroyed in order to carry out microbiological analyses. Tube nb 3, maintained in percolation, reached 99,4 % clogging after 142 days.MICROBIOLOGICAL RESULTS AND DISCUSSIONSampling procedures for analyses were set up by using tube nb 2. Three different samples of sand were used for analyses : from the inlet, from the middle and from the outlet of tubes nb 1 et 4. Moreover analyses were made on the percolation water upstream and downstream of tube nb 4.The revivifiable heterotrophic aerobic bacteria are more numerous in the water at the outlet of tube nb 4 than at the inlet, white direct counting shows a slight decrease.There are greater quantities of microorganisms in the sand than in the percolation water. The presence of sulfato-reducing bacteria can even be observed whereas they are too few to be counted in the percolation water. The filtering effect of the sand is not the only, element responsible for the increase amount of bacteria. Indeed the ratio between the number of revivifiable heterotrophic bacteria in the clogged tube and the non clogged tube was about 3 times greater than the ratio between their flow rates.The higher velocity in tube nb 4 induced favorable conditions for the development of certain species of bacteria, some of which generate hydrogen producing organic molecules, thus allowing the development of sulfato-reducing bacteria.Clogging itself should depend either on the increase of the biomass or on the development of microorganisms producing a significant quantity of organic molecules outside the cells. By taking into account the amount of bacteria and the volumes of percolated water, it can be seen that 2.01 x 1011 cells, i.e. 0.2 cm3 , were retained by filtration in tube nb 1, and 0.7 cm3 in tube nb 4. Basing the estimations on bacterial counts in the sand, biovolumes of 0.2 mm3 are obtained for tube nb 1 (non clogged), and 8 mm3 for tube nb 4 (clogged). Consequently the clogging substances consist mainly of products situated outside the cells.The tube is the center of chemolithotrophic organisms (made evident by C14 tracers), thus the aerobic heterotrophic microflora and the sulfato-reducing species are no doubt linked to the use of the metabolism products of these organisms.After 142 days percolation, the sand in tube nb 3 (clogged at 99,4 %) had a cell content of 1011 cells/cm3 of sand at the inlet (filamentous aggregates) and 107 cells/cm3 at the outlet (no aggregates). On an average, roughly a third of the pore volume is filled with cells, which is in agreement with a decrease in porosity from 35 to 27 % and therefore with the clogging in the tubes.CONCLUSIONTubes of sand could be clogged experimentalty and rapidly. The most significant clogging was obtained for the fastest percolation rate.It seems as though clogging is due to a proliferation of bacteria, essentially oligotrophic, and to the creation of a nutrient-chain rising to the sulfato-reducing bacteria (which are heterotrophic).The clogging process described in the case of the Ypresian sand aquifer is certainly similar to the processes occurring in other granular aquifers.The model " clog-meter" could be used by water supptiers exploiting aquifers fiable to clogging. Indeed it can determine the best flow rate, to avoid clogging in newly exploited pumping fields and decide on the most adequate well equipment, the number of wells needed in newly exploited areas and their exploitation yield in order to obtain the desired flow rates

Morphology and Orientation Selection of Non-Metallic Inclusions in Electrified Molten Metal

The effect of electric current on morphology and orientation selection of non-metallic inclusions in molten metal has been investigated using theoretical modelling and numerical calculation. Two geometric factors, namely the circularity (fc) and alignment ratio (fe) were introduced to describe the inclusions shape and configuration. Electric current free energy was calculated and the values were used to determine the thermodynamic preference between different microstructures. Electric current promotes the development of inclusion along the current direction by either expatiating directional growth or enhancing directional agglomeration. Reconfiguration of the inclusions to reduce the system electric resistance drives the phenomena. The morphology and orientation selection follows the routine to reduce electric free energy. The numerical results are in agreement with our experimental observations

The European language technology landscape in 2020 : language-centric and human-centric AI for cross-cultural communication in multilingual Europe

Multilingualism is a cultural cornerstone of Europe and firmly anchored in the European treaties including full language equality. However, language barriers impacting business, cross-lingual and cross-cultural communication are still omnipresent. Language Technologies (LTs) are a powerful means to break down these barriers. While the last decade has seen various initiatives that created a multitude of approaches and technologies tailored to Europe’s specific needs, there is still an immense level of fragmentation. At the same time, AI has become an increasingly important concept in the European Information and Communication Technology area. For a few years now, AI – including many opportunities, synergies but also misconceptions – has been overshadowing every other topic. We present an overview of the European LT landscape, describing funding programmes, activities, actions and challenges in the different countries with regard to LT, including the current state of play in industry and the LT market. We present a brief overview of the main LT-related activities on the EU level in the last ten years and develop strategic guidance with regard to four key dimensions

Antipollution pétrolière : caractérisation des produits dispersants par des essais de laboratoire (conférence)

L'emploi des dispersants pour lutter contre une pollution pétrolière vise à faciliter l'autoépuration du milieu chaque fois que les moyens mécaniques de récupération des hydrocarbures sont inemployables. Il s'agit de tensioactifs, souvent en solution dans des solvants, dont les propriétés permettent d'augmenter l'aire interfaciale huile/eau et ainsi accroître la cinétique de dégradation naturelle des fractions pétrolières dont la non-persistance est actuellement reconnue. Le choix des formulations des dispersants commerciaux doit répondre à des exigences écologiques quant à leurs propres toxicités vis-à-vis des êtres aquatiques et du personnel chargé de leur mise en oeuvre, dans un rapport dispersant/hydrocarbure qui doit être le plus faible possible. Malheureusement l'autoépuration des hydrocarbures dispersés n'étant pas magiquement immédiate, le milieu se trouve transitoirement au contact de la fraction pétrolière polluante qui, par le fait même de sa dispersion, est plus agressive pour les espèces les plus sensibles. La dispersion du pétrole est donc une arme difficile à manier et le choix des meilleurs produits dépend le plus souvent des conditions locales. Une présélection est possible et le Ministère de l'Environnement prépare un projet d'homologation basé sur les trois critères indépendants : efficacité du nettoyage, toxicité, dégradation du pétrole. Les méthodes de laboratoire n'ont pas la prétention de simuler les conditions naturelles, mais en plaçant tous les produits soumis à l'examen dans des conditions reproductibles, elles permettent d'observer et de mesurer des actions. Une méthode simple est actuellement proposée en vue de déterminer le rapport dispersant/hydrocarbure efficace pour obtenir une émulsion du pétrole et ensuite étudier les effets toxiques du mélange ainsi que sa biodégradation

Rapport VI.2. Conséquences d’un déversement d’hydrocarbures dans le sol et techniques applicables à une réhabilitation

Parameters on which depend the effects and the evolution of hydrocarbons in soil are now better known owing to fundamental studies and experience gained on the field. This knowledge of physico-chemical, biological, geological and technical nature will allow to assess the action of oil with regard to plants, soil microorganisms and groundwater. The study of soil conditions in case of chronic contact with petroleum components emphasizes the natural resistance of certain species (flora and microflora) and enables to determine the conditions that should be maintained to ensure their development. A programme for the rehabilitation of contaminated soil should take advantage of its natural ability for self-reclamation.Les paramètres qui conditionnent les effets des hydrocarbures dans le sol et leur évolution dans le temps sont maintenant mieux connus grâce à des études fondamentales associées à l’expérience acquise sur le terrain. Ces connaissances d’ordre physico-chimique, biologique, technologique et géologique permettent d’estimer le rôle des hydrocarbures vis-à-vis de la couverture végétale, des aquifères et des microorganismes du sol. L’examen de la situation des sols en contact chronique avec des fractions pétrolières met en évidence la résistance naturelle de certaines espèces (flore et microflore) et permet de définir les conditions à maintenir pour en assurer le développement. Un programme de réhabilitation d’un sol contaminé devrait tirer profit de son potentiel naturel d’autoépuration.Gatellier C., Gudin C., Rogier Ph. Rapport VI.2. Conséquences d’un déversement d’hydrocarbures dans le sol et techniques applicables à une réhabilitation. In: Influence des activités de l'homme sur le cycle hydrométéorologique. Compte-rendu des treizièmes journées de l'hydraulique. Paris, 16-18 septembre 1974. Tome 2, 1975

Le pétrole et son évolution après un épandage accidentel en mer. I. L'évolution primaire Oil and How It Evolves After an Accidental Offshore Spill. I. Primary Evolution

Cet article fait l'état des connaissances sur l'évolution au cours des premiers jours d'une coupe pétrolière accidentellement répandue en mer. Cette évolution primaire se fait sous les influences simultanées de l'étalement, de l'évaporation, de la dissolution, de la dispersion et parfois de la sédimentation. Au cours de cette évolution les modifications de la composition chimique des coupes pétrolières se traduisent par de nouvelles propriétés physiques, qui à leur tour influent sur le comportement du pétrole en mer. Un second article doit faire l'état des connaissances sur la suite des modifications que peut subir la coupe pétrolière quand, n'ayant pas disparu ou n'ayant pu être, ramassée, elle continue à évoluer. <br> This article reviews what is known about how on ail cut evolves during the first few days after having been accidentally spilled of sea. This initial evolution occurs under the simultaneous influences of spreading, evaporation, dissolution, dispersion and sometimes sédimentation. During this evolution, changes in the chemical composition of cil cuts are revealed by new physical properties which in turn influence the behavior of ail at sec. A second article will review what is known about the subsequent changes the ail cut moy undergo as if continues to evolve when it hos not disopoeared or been, oicked up

Etudes des relations oxydatives entre les lipides membranaires et la myoglobine in vitro

National audienc

Control of complex inclusions during metallurgical treatments on liquid and solid steels

Adequate physical and mechanical properties, for numerous steel grades, can be obtained only with a precise control of the composition, morphology and plasticity of oxide and sulphide inclusions that remain in the product. In liquid metal, the composition of complex inclusions can be monitored by appropriate deoxidation practice, calcium treatment and/or slag-metal reaction. Further transformation may occur during solidification or heat treatments prior to hotrolling: reaction between oxides and sulphides, as well as recrystallisation of oxides. An analysis of these factors and of tools (thermodynamic models and laboratory experiments) which have been developed to comprehend and control them is presented

A comparative study of macromolecular substances of a Coorongite and cell walls of the extant alga Botryococcus braunii

A Coorongite sample of Lake Balkash (Kazakhstan, CIS) was analyzed in detail by 13C-NMR, FTIR, Curie point pyrolysisgas chromatographymass spectrometry, and by fractionation and derivatization with dimethyldisulphide of an off-line pyrolysate. Both the spectroscopic and the pyrolysis data indicate that the Coorongite was derived almost entirely of organic matter of the green microalga Botryococcus braunii race A. Homologous series of n-alkanes and n-alk-1-en-9 in all pyrolysates indicated the presence of algaenan, a highly aliphatic and resistant cell wall biomacromolecule of B. Braunii race A. Highly specific pyrolysis products, in particular n-alkadienes, n-alkatrienes, alk-1-en-9-ones, and alk-1-en-10-ones with C27, C29, and C31 carbon atoms clearly indicated that C27, C29, and C31 alkadienes and alkatrienes, originally present in B. braunii race A as such, were cross-linked by oxygen during the very early stages of diagenesis under oxic conditions. Furthermore, several types of dialkenylethers, also present as soluble lipids in B. braunii race A, had undergone cross-linking by oxygen as well. These cross-linked lipids contribute significantly to the Coorongite and clearly demonstrate that under specific conditions kerogen consists of both preserved biomacromolecules and insoluble, cross-linked, low-molecular-weight lipids