Retention and diffusion of radioactive and toxic species on cementitious systems: Main outcome of the CEBAMA project

Cement-based materials are key components in radioactive waste repository barrier systems. To improve the available knowledge base, the European CEBAMA (Cement-based materials) project aimed to provide insight on general processes and phenomena that can be easily transferred to different applications. A bottom up approach was used to study radionuclide retention by cementitious materials, encompassing both individual cement mineral phases and hardened cement pastes. Solubility experiments were conducted with Be, Mo and Se under high pH conditions to provide realistic solubility limits and radionuclide speciation schemes as a prerequisite for meaningful adsorption studies. A number of retention mechanisms were addressed including adsorption, solid solution formation and precipitation of radionuclides within new solid phases formed during cement hydration and evolution. Sorption/desorption experiments were carried out on several anionic radionuclides and/or toxic elements which have received less attention to date, namely: Be, Mo, Tc, I, Se, Cl, Ra and 14C. Solid solution formation between radionuclides in a range of oxidation states (Se, I and Mo) with the main aqueous components (OH−, SO4 −2, Cl−) of cementitious systems on AFm phases were also investigated

Bio-encrassement par micro-irrigation : influence des conditions hydrodynamiques sur la structure et les communautés microbiennes des biofilms

International audienceBiofilm formation (accumulation of microorganisms, particles and algae) is a major factor in fouling of microirrigation systems using treated wastewater. Emitter Dripper clogging is significantly related to the flow characteristics but little is known about the effect of this factor on the biofilm development in a the reuse context. Moreover, the microbial community of these biofilms is unknown and sanitary questions related to these biofilms appear. In order to understand bioclogging biofouling phenomenon, the hydrodynamic effects must be understood and analyzed. Microirrigation system at lab scale have been set up with several drippers (1, 2 & 4 L.h-1), which were fed by treated wastewater. Evolution of biofilms was followed characterized by Optical tomography coherence (OCT) and microbiological analysis (qPCR & MiSeq Illumina) to determine the kinetics of development of the biofilmand possible pathogen accumulations (Escherichia coli quantification). To date, these measurements allowed to highlight different structures of biofilms and growing kinetic of biofilms (porosity, thickness) according to the dripper types and flow behaviors . The density of biofilms in drippers 2 and 4 L.h-1 were higher and a stratification of biofilms appeared with time . Microbial analysis and Escherichia coli quantification will be realized to explore the microorganisms responsible of this biofouling and the pathogen risk in a case of detachment

Drip irrigation biofouling with treated wastewater: bacterial selection revealed by high-throughput sequencing

International audienceClogging of drippers due to the development of biofilms weakens the advantages and impedes the implementation of drip irrigation technology. The objective of this study was to characterise the bacterial community of biofilms that develop in a drip irrigation system supplied with treated wastewater. High-throughput sequencing of 16S rRNA gene amplicons indicated that the bacterial community composition differed between drippers and pipes, mainly due to changes in the abundance of the genus Aquabacterium. Cyanobacteria were found to be involved in the biological fouling of drippers. Moreover, bacterial genera including opportunistic pathogenic bacteria such as Legionella and Pseudomonas were more abundant in dripper and pipe biofilms than in the incoming water. Some genera such as Pseudomonas were mostly recovered from drippers, while others (ie Bacillus, Brevundimonas) mainly occurred in pipes. Variations in the hydraulic conditions and properties of the materials likely explain the shift in bacterial communities observed between pipes and drippers

Characterization of chemical and biological clogging and there interaction in a micro-irrigation system in the context of treated waste water reuse

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L'expérimentation agronomique à l'heure du matériel lowcost : cas de la plaine agricole de Chenoua (Tipaza)

International audienceDes essais expérimentaux sur des cultures de concombre sous abri ont été conduits dans la plaine agricole de Chenoua (Tipaza) pour déterminer les conditions de fonctionnement des réseaux de goutte à goutte existants utilisant des eaux d'épuration et des eaux de nappe. Nous montrons que grâce à du matériel de mesure "lowcost", il est possible de produire de l'information utile qui permet d'établir un bilan d'eau et d'azote (modélisation agronomique) d'une part, et de dégager des relations débit-pression susceptibles de comprendre le fonctionnement des réseaux de goutte à goutte d'autre part. Des gaines de goutte à goutte également low cost ont été installées pour une durée d'une à deux années. Des mesures de débits par la méthode volumétrique (éprouvette) et de la pression à l'aide de manomètres à basse pression (< 1 bar) ont été effectuées au niveau des goutteurs dans deux serres de concombre. Les mesures de débit ont concerné 16 goutteurs bien répartis soient quatre rampes, sur chacune quatre goutteurs ont été sélectionnés : 2 aux extrémités et 2 au milieu. Quand à la pression elle a été prise en 3points : à l'entrée, au milieu de la serre et à la sortie pour diagnostiquer un éventuel effet de la position des goutteurs sur le colmatage. Un suivi horaire de la température et de l'humidité à l'intérieur de la serre a été réalisé par l'utilisation des thermohygromètres et ce afin d'établir un bilan hydrique dans la serre

Parameters controlling chemical deposits in micro-irrigation with treated wastewater

International audienceMicro-irrigation with treated wastewater has the potential to be the most efficient irrigation technique, especially in water scarce areas. Its main disadvantage is the high sensitivity of the drippers to clog. This study focused only on the chemical precipitation mechanisms. In a batch chemical process in parallel with PHREEQC software, two temperatures (22 and 55°C), four pH (8, 8.5, 9 and 9.5) and CO2 partial pressure were tested. The aim was to analyze the quantity of precipitates and their crystalline nature and calculate the effects of these factors on the behavior of dissolved chemical elements in treated wastewater to be able to validate and calibrate a geochemical software in order to predict chemical precipitation. The amount of precipitate increases by increasing pH and temperature. Precipitates were analyzed using thermo gravimetric analysis (TGA) and X-ray diffraction (XRD). Calcium carbonate (CaCO3) in the form of calcite was found to be the predominant precipitate. Experimental and model results showed that the saturation index (SI) of calcite was found to be the factor that most frequently affected calcite precipitation. Calcite SI is pH, temperature and CO2 partial pressure dependent. In the case of irrigation, water equilibrium with atmospheric CO2 minimizes precipitation of calcite

Applicabilité du concept d'analyse du cycle de vie à l'agriculture irriguée avec des eaux usées traitées, l'exemple de Tipaza, Algérie

International audienceAlgeria is in the category of water-scarce countries according to the scarcity threshold set by the United Nations Development Program (UNDP) or the World Bank, which is 1,000 cubic meters per capita and year. The resource is currently estimated at 500 m3 and will only be 430 m3 in 2020, according GIECC projections. Accessible resources in Algeria are estimated at 18 billion m3, of which 10 billion are superficial resources (MRE, 2015). Agriculture is the largest consumer of water using about 64% of total water resources (Benmouffok, 2004). The controlled reuse of treated wastewater (Reuse) is seen as a solution for the future, requiring the implementation of a new interdisciplinary approach. These practices may impact the environment and a life-cycle analysis (LCA) approach makes it possible to understand and evaluate the technological options with regard to their respective impacts

Développement du biofilm à forte concentration en DCO et en particules minérales : application au cas des goutteurs de micro-irrigation pour la réutilisation des eaux usées

International audienceWastewater reuse can properly supply irrigation demand by adopting suitable techniques and practices. Micro-irrigation optimizes water application and minimizes health hazards and crop contamination risks. Nevertheless, clogging is a common problem when using drip irrigation. In this study, we focus on emitters clogging due to biological and physical deposits. Experiments were carried out to investigate the interaction between biofilm growth and mineral particle deposits on 3 types of online emitters using a 200 mg/L COD synthetic effluent with and without mineral particles (size range: 0 to 80 µm). Emitter performance was monitored using flow rate measurement. Moreover the deposits of mineral particles and biofilms were analyzed optically, collected and dried at 105°C for 24 hours. Biofilm and mineral deposit induces flow rate decrease from the 30th day of the experiment. However, without mineral particles, emitter flow rate decrease was more significant. Thus, mineral particles seem to have an abrasive effect on biofilm depending on flow structure.La réutilisation des eaux usées traitées (REUSE) peut subvenir à la demande en eau d'irrigation en utilisant des techniques économes en eau. La micro-irrigation permet d'optimiser les apports en eau et de réduire les risques sanitaires liés à la REUSE. Cependant, le colmatage des systèmes d'irrigation est un inconvénient majeur. Dans cette étude, nous nous intéressons au colmatage d'origine physique et biologique. Des expérimentations ont été réalisées pour étudier l'interaction entre le développement de biofilm et le dépôt de particules minérales dans 3 types de goutteurs en utilisant un effluent synthétique à 200 mg/L en DCO avec ou sans particules minérales (taille variant entre 0 et 80 µm). Le débit des goutteurs a été suivi au cours de l'expérimentation. De plus, les dépôts ont été analysés optiquement puis prélevés et séchés à 105°C pendant 24h. Le débit diminue à partir du 30ème jour d'expérimentation suite au développement de biofilm et au dépôt de particules. Cependant, la diminution du débit est plus importante sans l'ajout de particules minérales qui semblent avoir un effet abrasif sur le biofilm en fonction des conditions d'écoulement