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

Addressing Undernutrition in Nigeria: What Next?

This briefing sets out the Priorities for Action that emerged from an online discussion amongst experts from central and sub-national government, multilateral and bilateral development agencies, national and international non-governmental organisations, civil society organisations, and research institutions operating in different sectors and levels in Nigeria, and who share the same goal of ending undernutrition in Nigeria. Those advocating within and outside government for commitment and action to address undernutrition in Nigeria are encouraged to adopt and use these Priorities for Action to inform and guide their advocacy efforts

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

Semantic framework for context-aware monitoring of AAL ecosystems

International audienceThe Web of Objects is a new emerging concept that represents a new way of organizing physical or immaterial objects—or things—delivering a high level of services that can be discovered, composed, executed, and monitored. Building an ambient assisted living (AAL) ecosystem, according to this vision, is of great interest since it consists of multiple heterogeneous objects that need to be semantically and automatically interoperable. In this chapter, a new semantic framework for monitoring the AAL heterogeneous ecosystems is presented. This framework deals with context awareness and closed-world assumption (CWA) semantic reasoning in designing management rules and ontologies. It preserves, on one hand, the structural expressiveness provided by ontologies, through the compatibility with the W3C recommendations and, on the other hand, it takes advantage of the full benefit of the production rule reasoning. It is capable of dynamically detecting real-world objects and capturing their contexts, in order to identify the specific changes that are happening in the environment, to infer the current situation and to react accordingly. Context management is designed by combining the micro-concept ontology language into a set rules and queries using the SEMbySEM business rule language. These rules allow us to express high-level reasoning over context events, sent from the façade, while the queries allow us to generate high-level monitoring views, concerning manageable objects status and context, as well as their measures and produced activities. Conversely, the monitoring rules can trigger control actions that are translated, by the façade, into concrete operations on the targeted manageable object. In order to validate the proposed framework, a scenario dedicated to the safety of elderly people in smart homes is proposed and implemented hereby

Progress in Diesel Hcci Combustion Within the European Space Light Project

he purpose of the European "SPACE LIGHT" (Whole SPACE combustion for LIGHT duty diesel vehicles) 3-year project launched in 2001 is to research and develop an innovative Homogeneous internal mixture Charged Compression Ignition (HCCI) for passenger cars diesel engine where the combustion process can take place simultaneously in the whole SPACE of the combustion chamber while providing almost no NOx and particulates emissions. This paper presents the whole project with the main R&D tasks necessary to comply with the industrial and technical objectives of the project. The research approach adopted is briefly described. It is then followed by a detailed description of the most recent progress achieved during the tasks recently undertaken. The methodology adopted starts from the research study of the in-cylinder combustion specifications necessary to achieve HCCI combustion from experimental single-cylinder engines testing in premixed charged conditions. With such information collected, 1D CFD calculations are then used to evaluate the potential of different ways and concepts to provide the in-cylinder global conditions favorable to this combustion mode. Associated 3D CFD calculations complete these results by providing information about the potential of these concepts to achieve the specified local conditions inside the combustion chamber. Supported by all these calculations, by some optical diagnostics in transparent engines, by visualization and detailed characterization of the sprays of the new injection system developed, the design process of the most promising HCCI engine concept selected has been undertaken. It is based on a unique combination of flexible variable valve actuation technology, advanced injection system with "SPACE" spray pattern, air and EGR charging and mixing strategies,... The corresponding hardware has been manufactured and integrated in prototype single-cylinder engines. The most recent engine tests results achieved with the SPACE LIGHT diesel HCCI concept are presented and discussed. They already show impressive reduction of NOx and particulates as expected compared to conventional diesel combustion. The most interesting aspect is that the high efficiency of the best state-of-the-art diesel conventional combustion can be maintained. It opens a promising way to future powertrain engines mixing the highest efficiency of the diesel engines with the near-zero emission capability of the gasoline engine