Nouveaux procédés d'oxydation chimique pour l'élimination des rejets aqueux phénolés

Pour faire face au problème posé par les rejets aqueux chargés en phénol, deux procédés d'épuration par voie chimique sont proposés. Les deux méthodes font appel au peroxyde d'hydrogène. Celui-ci joue le rôle de promoteur de radicaux lors de l'oxydation de la charge organique par l'oxygène moléculaire dans le premier procédé qui s'inspire de la technique « Wet Air Oxidation » et constitue l'agent oxydant dans le second procédé intitulé « Wet Peroxide Oxidation ».L'introduction en continu de peroxyde d'hydrogène permet d'initier la réaction d'oxydation du phénol par l'oxygène moléculaire et de réduire considérable-ment les conditions de température et de pression de fonctionnement de la technique WAO classique. La réduction de la Demande Chimique en Oxygène de l'effluent dépasse 95 % à 160 °C en introduisant du peroxyde d'hydrogène à raison de 10 % de la quantité stoechiométrique nécessaire pour l'oxydation complète du phénol. Le second procédé consiste à utiliser l'oxydation par le peroxyde d'hydrogène en présence de fer ferreux (réactif de Fenton) dans des conditions de température (environ 120 °C) conduisant à un abattement important de la charge organique de l'effluent. A température élevée, la compétition entre la réaction de décomposition du peroxyde en oxygène moléculaire inactif et celle de décomposition en radicaux qui développent le processus d'oxydation engendre des conditions opératoires optimales pour lesquelles l'efficacité du procédé est maximale.Ces deux procédés apportent une solution technique satisfaisante pour traiter, avec un abattement important de la demande chimique en oxygène et du carbone organique, les effluents aqueux assez fortement chargés en composés phénolés.Despite of a growing concern about the problems of wastes elimination during the previous years, there is still a lack of processes in order to treat industrial aqueous wastes. Organic aqueous wastes and specially phenolic wastes, that can be either nonbiodegradable or toxic, give rise to one of the main problems. Landfilling disposal and related methods are a priori rejected as they appear to leaving the legacy of a problem we have net been able to solve rather than to considering our environment as being borrowed from the future mankind. Various oxidation techniques are suited for the elimination of this class of wastes. But, because of the environmental and economical drawbacks of incineration, it seems that liquid phase oxidation techniques should be preferred.The paper reviews : two liquid phase purification techniques using the chemical oxidation route; phenol being used as a test compound. The first technique is adapted from the wet air oxidation (WAO) process and uses molecular oxygen as the oxidizing agent. In the meantime, hydrogen peroxide is added at a low dosage and promotes the radicle reactions. Thus, the reaction temperature and pressure can be set at lower values (typically 160 °C, 25 bar) than usually. In this way, the conventional WAO process, which is very capital intensive because of temperature and pressure constraints is turned into a more affordable process. The second technique uses hydrogen peroxide as the oxidizer. it is associated to a ferrous salt as in the Fenton's reagent but it is run out under temperature (about 120 °C) so that a very important total organic carbon (TOC) removal efficiency con be obtained. This technique was named wet peroxide oxidation (WPO) process. As opposed to WAO, WPO needs only limited capital but generates higher running colts. Yet, both techniques can be regarded as efficient and economically satisfying in order to treat organic aqueous wastes containing fair amounts of phenol or phenolic compounds.The test compound was selected considering the frequent occurrence of phenol within the wastewaters of refineries, steel works and chemical industries. Their biological treatment is still very difficult for high concentrations despite of an important research activity. Treatment times and efficiencies of physicochemical methods are not but seldom satisfactory. Then, liquid phase oxidation methods have their whole interest. As it was reported that phenolic compounds (methylphenols, chloro-phenols) oxidation proceeds in a similar way than for phenol, the last molecule was considered for assessing the efficiency of both oxidation methods.The first method (WAO) was tested using a completely mixed batch reactor (stirred autoclave): The cold reactor was loaded with a phenol (2100 mg. 1-1) and ferrous sulfate (10 mg. l-11) solution al the convenient pH value (3.5). After heating at the rated temperature, the run was started by injecting instantaneously a large amount of oxygen (10 times the amount necessary). At the same time, a dosing pump was started and fed continuously hydrogen peroxide within the reactor all along the run (90 minutes). The total amount injected was usually 10 % of the amount necessary for a stoechiometric oxidation. The promoting effect of hydrogen peroxide on molecular oxygen is evidenced on figure 2 where the initiating period is shortened and on figure 3 where the oxidation efficiency actually obtained (curve 3) is greater than expected by adding the efficiencies of molecular oxygen and hydrogen peroxide oxidations if separated (curve 2). WAO promoted with hydrogen peroxide gave after 90 minutes better oxidation efficiencies at 160 °C than conventional WAO at 220 °C, then turning into a medium pressure process a high pressure one. The promoting effect of the peroxide is more marked at 160 °C than above 200 °C where a rapid decomposition occurs; dosages greater 15 % do not significantly increase the efficiency and dosages as small as 0,2 % have already a significant affect (see figure 5). Various compounds have been identified and the oxidation sequence is as follows : phenol -> dihydroxy-benzenes -> maleic acid -> oxalic, formic, acetic acids. Most of the remaining chemical oxygen demand (COD) of the oxidized solutions is acetic acid. Only more drastic experimental conditions allow its total removal.The WPO runs (second oxidation method) were conducted into a similar reactor. It was batch loaded with the phenol (2300 mg. 1-1) and ferrous sulfate (30 mg. l-1) solution at pH 3.5. After heating at 120 °C, the run was started and hydrogen peroxide was continuously fed using a dosing pump. The total amount injected all along the run (60 minutes) was the amount necessary for a stoechiometric oxidation. A similar oxidation sequence than reported hereon was observed; pyrocatechol, bydroquinone and oxalic acid were evidenced (figure 9) but, in this case, only very limited amounts of formic and acetic acids were detected. For the two processes, tables 2 and 3 summarize the material balances of the various products as a function of the oxidation time. A 90 % COD removal efficiency and a 70 % total organic carbon (TOC) removal efficiency is reported on figure 10. This result has to be compared with the TOC removal efficiencies (< 25 %) reported for the usual Fenton’s reagent at room temperature. The changes of the pH value and of the COD/TOC ratio (figure 11) during the run are easily explained by considering that oxalic acid is quite the sole product remaining after oxidation contrarily to promoted WAO where acetic acid is the major remaining product. Besides the production of radicles that bring on the oxidation process, a side-reaction decomposes hydrogen peroxide into molecular oxygen which is net active at such a low temperature. The competition between the two reactions makes optimum operating conditions to exist and to lead to a maximum efficiency of the process.Both processes bring on new methods in order to treat fairly concentrated phenolic solutions with a typical 90 % COD removal efficiency. The products remaining after oxidation (mainly acetic acid or oxalic acid) should not be regarded as a drawback of these processes. In actual fact, such compounds can be easily treated by adding a biological post-treatment unit to the chemical oxidation

Oxydation humide des polluants organiques par l'oxygène moléculaire activée par le couple H²O²/Fe²+: Optimisation des paramètres opératoires

L'oxydation humide par l'oxygène moléculaire (procédé WAO) activée par le couple (H202/Fe2+) a été mise en oeuvre pour l'oxydation de la pollution organique aqueuse à travers deux composés modèles: l'acide succinique, normalement oxydable, et l'acide acétique, réputé réfractaire. L'influence des différents facteurs a été étudiée par la planification d'expériences. Après leur recensement, une étape préliminaire de criblage a été menée à bien en utilisant une matrice de Plackett et Burman. Seuls les paramètres les plus influents ont été gardés pour l'étape ultérieure d'établissement de modèles prévisionnels à partir d'une matrice composite centrée orthogonale. Les modèles établis ont été validés et ont permis de déterminer les conditions optimales de fonctionnement. L'effet de la température fait apparaître un optimum, à environ 200 °C, au-delà duquel la décomposition du peroxyde devient trop rapide. L'effet de la quantité de peroxyde d'hydrogène introduit est déterminant et l'ajout de moins de 20 % de la quantité stoechiomé- trique permet d'obtenir à 200 °C, avec environ 10 ppm de sels de fer, une efficacité de traitement d'environ 70% pour un composé normalement oxydable. Dans des conditions analogues, le procédé conventionnel sans promoteur conduit à une efficacité inférieure à 5 %.Wet air oxidation (WAO) is a liquid phase oxidation process using molecular oxygen at high temperature (250-300°C) and high pressure (50-150 bar). It can help treating toxic organic aqueous wastes from chemical industries with efficiencies up to 98% after 1 hour. The process can also help treating sludges from domestic sewage treatment facilities. It is usually very cost effective because of the very high operating pressure.This paper deals with the promoted wet air oxidation of acetic acid, rnodel compound for refractory wastes, and succinic acid, model for readily oxidized wastes. The study was conducted in order to determine the promoting effect when adding small dosages of hydrogen peroxide (with iron salts) during oxidation by molecular oxygen. It was previously shown that the initiating step is very temperature dependent (Reaction I) and limits the overall oxidation process The addition of small amounts of H2O2/Fe2+ (Fenton's reagent) can promote the forrnation of very reactive OH• radicals able to develop R• radicals (Reaction IV), even at a low temperature. Then, the oxidation (Reactions VI and VII) continues using molecular oxygen, but the peroxide should be added continuously during a batch test in order to maintain the initiating step.An optimal design methodology was used in order to assess the dependency of the oxidation effrciency on the various parameters and mainly on the promotors. At frrst, a Plackett and Burman design of experiments (PE1) was used to screen the most important variables among those likely to have an effect. The design of experiments, the conditions of the runs and the results (tables 1 to 3) allowed the determination of a new experimental domain and the selection of the four most important variables for the further design of experiments. At the same time, the effect of an addition of phenol (able to reduce iron to the ferrous species, more efficient) was considered. For succinic acid oxidation, a central composite optimal design (PE2) was used (tables 4 and 5). The results allowed us to establish a predictive model (Relationship lX, table 6 and figure 2) and typical results are presented in figures 3 and 4. Approximately 50% oxidation efficiencies could be obtained at 200°C; without peroxide addition, only 5% efficiency is obtained under similar conditions. Moreover, it was observed that the optimum temperature is around 205°C and that phenol is not compatible with peroxide as a promotor. A third optimal design (PE3) was used to predict the efficiency of the method for the treatrnent of acetic acid, a model for a refractory waste. It is composed only of a fractional factorial design (table 7 and 8) and the bias corresponds to the main quadratic effect of temperature (Relationship XIII and table 10). The optimum temperâture is also 205°C and greater than 20% oxidation efficiencies are obtained; at such a temperature, acetic acid cannot be oxidized with the conventional process.The results obtained for the two model compounds validate this oxidation technique. The addition of about 10 ppm of ferrous iron and of less than 20% of the stoichiometric amount in hydrogen peroxide can turn a high pressure WAO process into a medium pressure one

Reducing waste generated by international students- mobility-improving user experience with object detectionn

International student mobility is on the rise. Even though international exchange programs foster intercultural development, some contend that the environmental impact must be considered more. This work project focuses on one piece of the complex puzzle: overconsumption. In line with SDG 12, we propose an application called Repurpose, aimed at effectively repurposing everyday items new international students buy but would otherwise throw away at the end of their curriculum. The application is tailored to the global Gen Z audience, leveraging AI for convenient experiences and considering the time gap when international students leave and arrive. Due to its scalable SaaS nature and considerate business model, the app has the chance to grow into a critical application for international students worldwide. This report contains both common part prepared by the project team together and an individual part that was about object detection and how it can be implemented in a low code environment to improve the user experience

Resource allocation methods for quality-of-service provisioning in heterogeneous wireless networks

The increased use of mobile wireless devices that we have recently been witnessing, such as smartphones, tablets, e-readers, and WiFi enabled devices in general, is driving an unprecedented increase in the amount of data traffic. This fast market adoption of the wireless technology along with the tremendous success of multimedia applications brought about higher capacity, connectivity, and Quality of Service (QoS) requirements that can no longer be met with traditional networking paradigms. As a result, heterogeneous wireless networks have recently emerged as a potential solution for meeting such new requirements. Hybrid wireless mesh networks and femtocell/macrocell networks are examples of these newly emerging heterogeneous networks. While mesh networks are viewed as the backbone/core network, femtocell and cellular networks are viewed as the access networks linking end-users with the backbone networks. In this dissertation, we address the problem of resource allocation in heterogeneous networks. We investigate both types of networks/architectures: next-generation wireless backbone networks or simply wireless mesh networks (WMNs) and next-generation wireless access networks or simply femtocell (FC) networks. WMNs were first introduced to foster the availability of Internet services anywhere and at anytime. However, capacity limitation has been a fundamental challenge to WMNs, mainly due to the interference arising from the wireless nature of the environment as well as to the scarcity of the radio/channel resources. To overcome this problem, we propose in this dissertation an efficient scheduling scheme that reduces interference among active links via wise time and frequency assignments to the wireless mesh routers. The developed scheme is traffic aware in that it maximizes the capacity of wireless links but while accounting for their traffic loads, thus meeting the end-to-end bandwidth requirements as much as possible. In the second part of this thesis, we focus on developing power allocation techniques for FC networks. FCs have recently emerged as a key networking solution that has great potential for improving the capacity and coverage of traditional macrocell (MC) networks through high-speed indoor coverage. Their deployment, however, has given rise to new interference challenges which are mainly due to the FCs' autonomous nature and to the unreliability of the wireless medium. Driven by this fact, in the second part of this thesis, we first design a fully-distributed estimation-based power allocation scheme that aims at fairly maximizing the capacity of FC networks. Second, we propose a novel distributed stochastic power control scheme that aims at maintaining the users' minimum= required QoS. Finally, we provide cross-layer performance analysis of two-tier FC networks, in which we characterize the uplink interference and study its impact on the data-link layer QoS performance in FC networks

DNA Methylation Dynamics in the Female Germline and Maternal-Effect Mutations That Disrupt Genomic Imprinting.

Genomic imprinting is an epigenetic marking process that results in the monoallelic expression of a subset of genes. Many of these 'imprinted' genes in mice and humans are involved in embryonic and extraembryonic growth and development, and some have life-long impacts on metabolism. During mammalian development, the genome undergoes waves of (re)programming of DNA methylation and other epigenetic marks. Disturbances in these events can cause imprinting disorders and compromise development. Multi-locus imprinting disturbance (MLID) is a condition by which imprinting defects touch more than one locus. Although most cases with MLID present with clinical features characteristic of one imprinting disorder. Imprinting defects also occur in 'molar' pregnancies-which are characterized by highly compromised embryonic development-and in other forms of reproductive compromise presenting clinically as infertility or early pregnancy loss. Pathogenic variants in some of the genes encoding proteins of the subcortical maternal complex (SCMC), a multi-protein complex in the mammalian oocyte, are responsible for a rare subgroup of moles, biparental complete hydatidiform mole (BiCHM), and other adverse reproductive outcomes which have been associated with altered imprinting status of the oocyte, embryo and/or placenta. The finding that defects in a cytoplasmic protein complex could have severe impacts on genomic methylation at critical times in gamete or early embryo development has wider implications beyond these relatively rare disorders. It signifies a potential for adverse maternal physiology, nutrition, or assisted reproduction to cause epigenetic defects at imprinted or other genes. Here, we review key milestones in DNA methylation patterning in the female germline and the embryo focusing on humans. We provide an overview of recent findings regarding DNA methylation deficits causing BiCHM, MLID, and early embryonic arrest. We also summarize identified SCMC mutations with regard to early embryonic arrest, BiCHM, and MLID

Loss of the Maternal Effect Gene Nlrp2 Alters the Transcriptome of Ovulated Mouse Oocytes and Impacts Expression of Histone Demethylase KDM1B

The subcortical maternal complex (SCMC) is a multiprotein complex in oocytes and preimplantation embryos that is encoded by maternal effect genes. The SCMC is essential for zygote-to-embryo transition, early embryogenesis, and critical zygotic cellular processes, including spindle positioning and symmetric division. Maternal deletion of Nlrp2, which encodes an SCMC protein, results in increased early embryonic loss and abnormal DNA methylation in embryos. We performed RNA sequencing on pools of meiosis II (MII) oocytes from wild-type and Nlrp2-null female mice that were isolated from cumulus-oocyte complexes (COCs) after ovarian stimulation. Using a mouse reference genome-based analysis, we found 231 differentially expressed genes (DEGs) in Nlrp2-null compared to WT oocytes (123 up- and 108 downregulated; adjusted p\u3c0.05). The upregulated genes include Kdm1b, a H3K4 histone demethylase required during oocyte development for the establishment of DNA methylation marks at CpG islands, including those at imprinted genes. The identified DEGs are enriched for processes involved in neurogenesis, gland morphogenesis, and protein metabolism and for post-translationally methylated proteins. When we compared our RNA sequencing data to an oocyte-specific reference transcriptome that contains many previously unannotated transcripts, we found 228 DEGs, including genes not identified with the first analysis. Interestingly, 68% and 56% of DEGs from the first and second analyses, respectively, overlap with oocyte-specific hyper- and hypomethylated domains. This study shows that there are substantial changes in the transcriptome of mouse MII oocytes from female mice with loss of function of Nlrp2, a maternal effect gene that encodes a member of the SCMC

Comparison of Four Protocols for In Vitro Differentiation of Human Embryonic Stem Cells into Trophoblast Lineages by BMP4 and Dual Inhibition of Activin/Nodal and FGF2 Signaling

Human embryonic stem cells (hESCs) cultured in media containing bone morphogenic protein 4 (BMP4; B) differentiate into trophoblast-like cells. Supplementing media with inhibitors of activin/nodal signaling (A83-01) and of fibroblast growth factor 2 (PD173074) suppresses mesoderm and endoderm formation and improves specification of trophoblast-like lineages, but with variable effectiveness. We compared differentiation in four BMP4-containing media: mTeSR1-BMP4 only, mTeSR1-BAP, basal medium with BAP (basal-BAP), and a newly defined medium, E7-BAP. These media variably drive early differentiation towards trophoblast-like lineages with upregulation of early trophoblast markers CDX2 and KRT7 and downregulation of pluripotency markers (OCT4 and NANOG). As expected, based on differences between media in FGF2 and its inhibitors, downregulation of mesendoderm marker EOMES was variable between media. By day 7, only hESCs grown in E7-BAP or basal-BAP expressed HLA-G protein, indicating the presence of cells with extravillous trophoblast characteristics. Expression of HLA-G and other differentiation markers (hCG, KRT7, and GCM1) was highest in basal-BAP, suggesting a faster differentiation in this medium, but those cultures were more inhomogeneous and still expressed some endodermal and pluripotency markers. In E7-BAP, HLA-G expression increased later and was lower. There was also a low but maintained expression of some C19MC miRNAs, with more CpG hypomethylation of the ELF5 promoter, suggesting that E7-BAP cultures differentiate slower along the trophoblast lineage. We conclude that while all protocols drive differentiation into trophoblast lineages with varying efficiency, they have advantages and disadvantages that must be considered when selecting a protocol for specific experiments

Reconstruction 3D de sténoses par modélisation markovienne à partir de plus de deux images d'angiographie rotative par rayons X

- Dans cette contribution, nous proposons une méthode de reconstruction tridimensionnelle (3D) locale de sténoses à partir de plus de deux images ou projections extraites d'une séquence d'images d'angiographie rotative par rayons X. Cette méthode utilise une modélisation markovienne dont l'énergie comprend un terme décrivant l'a priori sur la structure vasculaire à reconstruire ainsi qu'un terme d'ajustement aux projections. Cette modélisation est une généralisation de celle introduite dans [1]. En effet, l'énergie d'ajustement est modifiée afin de prendre en compte un nombre de projections supérieur à deux. Cette généralisation augmente le nombre de contraintes ce qui diminue le nombre de minima globaux de l'énergie markovienne. Les simulations réalisées dans ce travail montre que cela améliore sensiblement la qualité de la reconstruction dans le cas de présence de sténoses de formes complexes

Modeling-based optimization approaches for the development of Anti- Agrobacterium tumefaciens activity using Streptomyces sp TN71

A new aerobic bacterium TN71 was isolated from Tunisian Saharan soil and has been selected for its antimicrobial activity against phytopathogenic bacteria. Based on cellular morphology, physiological characterization and phylogenetic analysis, this isolate has been assigned as Streptomyces sp. TN71 strain. In an attempt to increase its anti-Agrobacterium tumefaciens activity, GYM + S (glucose, yeast extract, malt extract and starch) medium was selected out of five different production media and the medium composition was optimized. Plackett-Burman design (PBD) was used to select starch, malt extract and glucose as parameters having significant effects on antibacterial activity and a Box-Behnken design was applied for further optimization. The analysis revealed that the optimum concentrations for anti-A. tumefaciens activity of the tested variables were 19.49 g/L for starch, 5.06 g/L for malt extract and 2.07 g/L for glucose. Several Artificial Neural Networks (ANN): the Multilayer perceptron (MLP) and the Radial basis function (RBF) were also constructed to predict anti-A. tumefaciens activity. The comparison between experimental with predicted outputs from ANN and Response Surface Methodology (RSM) were studied. ANN model presents an improvement of 12.36% in terms of determination coefficients of anti A. tumefaciens activity. To our knowledge, this is the first work reporting the statistical versus artificial intelligence based modeling for optimization of bioactive molecules against phytopathogen

Adaptive Beacon Broadcast in Opportunistic Routing for VANETs

Broadcast of beacon messages including geographic coordinates, node speeds, and directions are among the most commonly used methods in routing protocols of VANETs to obtain neighboring positions. Broadcast of periodic beacon messages in fixed time intervals will reduce network performance due to increased channel load and contention. In this paper, an adaptive update strategy for sending beacon messages according to the VANETs’ characteristics (position, speed, and direction) and the nature of broadcast wireless channel in an opportunistic routing strategy is studied. It is based on two rules: 1) an estimation of the lifetime of the links between vehicles’ beacon messages are sent after the expiration of the estimated time to inform their local topology and 2) if the forwarding set of consecutively received data packets is changed, a beacon message is sent to maintain the accuracy of the topology. The simulation results show that the proposed strategy significantly reduces the cost of routing and improves network performance in terms of packet-delivery ratios, average end-to-end delay, and routing overhead