Interaction entre l’élimination des polluants azotés et la formation des granules aérobies en réacteur biologique séquencé

Le procédé à boues granulaires aérobie constitue une technologie prometteuse pour le traitement des pollutions azotées\ud mais son application industrielle nécessite de comprendre certains verrous scientifiques de façon à optimiser les conditions de\ud fonctionnement notamment en minimisant les besoins énergétiques. La structure spécifique des granules aérobies génère\ud naturellement des limitations au transfert des polluants et une organisation spatiale beaucoup plus hétérogène que dans les flocs.\ud Les bactéries autotrophes et hétérotrophes sont alors en interaction ou en compétition. Ainsi l’objectif de ce travail est, au travers\ud de deux études expérimentales, de mieux comprendre les interactions entre la croissance/respiration en anoxie/aérobie et la\ud structuration des boues granulaires ainsi que leurs performances pour l’élimination de l’azote.\ud Dans la première expérience, deux réacteurs SBR sont étudiés parallèlement en maintenant une concentration en oxygène\ud de 1,8±0,8 mg L-1. Un seul des deux réacteurs reçoit une charge en nitrate (50-200 mg N L-1). Dans le réacteur alimenté en\ud nitrate les agrégats présentent des propriétés très proches de celles des granules aérobies alors que le système de référence\ud purement aérobie présente des propriétés de décantation plus comparables à celles des biomasses floculées. L’observation des\ud cinétiques et des bilans azote montre que la dénitrification a lieu à l’intérieur des agrégats dans des zones internes où l’oxygène\ud est très probablement limitant du fait des fortes activités spécifiques des agrégats microbiens et de la densification de ces\ud agrégats. Un modèle mathématique développé sous AQUASIM® permet de décrire les gradients de concentrations dans les\ud granules (1 dimension) et l’évolution des espèces au cours du temps dans le réacteur. Ce modèle intégrant les phénomènes de\ud respiration/croissance/stockage des espèces hétérotrophes en aérobie et en anoxie a permis de décrire l’effet des nitrates sur la\ud croissance hétérotrophe. Non seulement le profil de biomasse active montre une croissance plus en profondeur mais ceci génère\ud également plus de stockage de composés de réserve. Enfin le modèle traduit le fait que la croissance plus en profondeur (générée\ud par la présence de nitrates) constitue un moyen de mieux protéger la biomasse active du détachement par érosion.\ud Dans la deuxième expérience, deux réacteurs identiques de type «air-lift » sont opérés avec des stratégies d’aération\ud différentes : dans le premier un débit d’air relativement modéré (SAV=0,6 cm s-1) et une alternance anoxie/aérobie sont imposés\ud (un complément en nitrate est maintenu pour éviter l’anaérobie), alors que dans le deuxième réacteur le débit d’air est élevé\ud (SAV= 2,83 cm s-1) et les conditions principalement aérobies. Les résultats démontrent que l’alternance entre des conditions\ud d’excès « anoxie » et de famine « aérobie » permettent de favoriser le développement des granules aérobies (la taille des granules\ud est entre 500-1000 Bm) et la stabilisation des performances (nitrification en particulier). La caractérisation physique (taille et\ud cohésion) des agrégats biologiques montre que les granules sont des agrégats microbiens dont la densité est plus élevée que celle\ud des flocs et dont la cohésion est suffisante pour que leur taille ne soit pas calibrée par l’échelle de la turbulence ; la formation des\ud granules est caractérisée par plusieurs étapes : une phase de densification, une phase de croissance avec érosion (distribution\ud bimodale), puis une phase de croissance et de maturation.----------------------------------------------------------------------------------------------Aerobic granular sludge process is a feasible technology for the treatment of nitrogen pollution, but some key points need\ud to be further understood in order to optimize the operational conditions for its industrial application, especially considering the\ud minimization of energy requirements. The special structure of aerobic granules generates naturally the pollutants transfer limit\ud within granules. The spatial organization is much more heterogeneous than that in the flocs. The autotrophic bacteria and\ud heterotrophic bacteria are interacting or competing. Thus the goal of this work is, in two experimental studies, to better\ud understand the interactions between the growth / respiration under the anoxic/aerobic conditions and the structure of granular\ud sludge as well as their performance for nitrogen removal.\ud In the first experiment, two parallel SBR reactors are installed maintaining a dissolved oxygen concentration of 1.8±0.8\ud mg L-1. Nitrate (50-200 mg N L-1) was only added in the influent of one reactor, in which the aggregates properties were\ud comparable to aerobic granules, while the aggregates properties in the other reactor were more traditional (floc-like). The kinetic\ud observation and nitrogen measurement show that denitrification occurs within the aggregates where the DO is probably limited\ud because of high specific biological activities and the density of biological aggregates. A developing mathematical model by the\ud software tool AQUASIM® allows describing the concentration gradients of substrates in the granules (1 dimension) and the\ud evolution of biological species in the reactor. This model including the phenomena of respiration / growth / storage of\ud heterotrophic species in aerobic and anoxic conditions helps to describe the effect of nitrate on the heterotrophic growth. Not\ud only the profile of active biomass shows a growth in more depth but also generates more storage compounds. Finally, this model\ud reveals that heterotrophic growth in more depth (generated by the presence of nitrate) protect well the active biomass to avoid the\ud detachment by erosion.\ud In the second experiment, two airlift reactors worked on the different aeration strategies: a relatively moderate air flow\ud rate (SAV = 0.6 cm s-1) and alternating anoxic / aerobic conditions are applied in the first reactor (additional nitrate is maintained\ud to avoid anaerobic condition), whereas a high air flow rate (SAV = 2.83 cm s-1) and strictly aerobic conditions maintain in the\ud second reactor. The results show that the alternating anoxic feast / aerobic famine conditions encourage the formation of aerobic\ud granules (the size is between 500-1000 Bm) and the stabilization of nitrification performance. The aggregates strength test shows\ud that the density of aerobic granules is higher than the flocs. The size of aerobic granules is not calibrated by the Kolmogorov\ud micro-scale. The formation of granules is characterized by several stages: a stage of densification, an expansion phase with\ud particles erosion (bimodal distribution), then a growth phase and a maturation

Neutralizing antibody response in the patients with hand, foot and mouth disease to enterovirus 71 and its clinical implications

Enterovirus 71 (EV71) has emerged as a significant pathogen causing large outbreaks in China for the past 3 years. Developing an EV71 vaccine is urgently needed to stop the spread of the disease; however, the adaptive immune response of humans to EV71 infection remains unclear. We examined the neutralizing antibody titers in HFMD patients and compared them to those of asymptomatic healthy children and young adults. We found that 80% of HFMD patients became positive for neutralizing antibodies against EV71 (GMT = 24.3) one day after the onset of illness. The antibody titers in the patients peaked two days (GMT = 79.5) after the illness appeared and were comparable to the level of adults (GMT = 45.2). Noticeably, the antibody response was not correlated with disease severity, suggesting that cellular immune response, besides neutralizing antibodies, could play critical role in controlling the outcome of EV71 infection in humans

MSGNet: multi-source guidance network for fish segmentation in underwater videos

Fish segmentation in underwater videos provides basic data for fish measurements, which is vital information that supports fish habitat monitoring and fishery resources survey. However, because of water turbidity and insufficient lighting, fish segmentation in underwater videos has low accuracy and poor robustness. Most previous work has utilized static fish appearance information while ignoring fish motion in underwater videos. Considering that motion contains more detail, this paper proposes a method that simultaneously combines appearance and motion information to guide fish segmentation in underwater videos. First, underwater videos are preprocessed to highlight fish in motion, and obtain high-quality underwater optical flow. Then, a multi-source guidance network (MSGNet) is presented to segment fish in complex underwater videos with degraded visual features. To enhance both fish appearance and motion information, a non-local-based multiple co-attention guidance module (M-CAGM) is applied in the encoder stage, in which the appearance and motion features from the intra-frame salient fish and the moving fish in video sequences are reciprocally enhanced. In addition, a feature adaptive fusion module (FAFM) is introduced in the decoder stage to avoid errors accumulated in the video sequences due to blurred fish or inaccurate optical flow. Experiments based on three publicly available datasets were designed to test the performance of the proposed model. The mean pixel accuracy (mPA) and mean intersection over union (mIoU) of MSGNet were 91.89% and 88.91% respectively with the mixed dataset. Compared with those of the advanced underwater fish segmentation and video object segmentation models, the mPA and mIoU of the proposed model significantly improved. The results showed that MSGNet achieves excellent segmentation performance in complex underwater videos and can provide an effective segmentation solution for fisheries resource assessment and ocean observation. The proposed model and code are exposed via Github1

The Effect of Social Exclusion on Trust Among Youth Orphaned by HIV/AIDS: Evidence From an Event-Related Potentials Study

Grounded in a follow-up study among children who lost one or both parents to HIV in central China in the early 2000s, we conducted an event-related potentials (ERPs) experiment to explore the effect of social exclusion on trust and the corresponding neurophysiological mechanism among youth orphaned by HIV/AIDS (“AIDS orphans”). A sample of 31 AIDS orphans (26.16 ± 3.34 years old; 15 female) and 32 age and development status matched controls (25.02 ± 3.45 years old; 14 female) participated in the study. They were all assigned to play Cyberball, a virtual ball-tossing game that reliably induced social exclusion (15 orphans, 16 controls) and inclusion (16 orphans, 16 controls). Then, they played the Trust Game by taking the role of trustor with their electroencephalograms (EEGs) being recorded during the game. In the Trust Game, each participant was required to decide whether to trust their partners in over 150 trials (decision-making stage). The partner’s reciprocation strategies were pre-programmed by the experimenter (with an overall reciprocating rate of 50%). All participants were provided with post-decision feedback about the outcome of their decisions (gain or loss of game points) in each trial (outcome evaluation stage). We analyzed their behavioral responses at the decision-making stage and ERP components at the outcome evaluation stage. Behavioral results showed that the proportion of orphans choosing trust was significantly higher than the controls, and the trust ratio of the orphan exclusion (OE) group was significantly higher than that of the orphan inclusion (OI) group, control exclusion (CE) group, and control inclusion (CI) group. Furthermore, the response time of the OE group was significantly shorter than that of other groups. ERP results indicated that the amplitude of the feedback-related negativity (FRN) in the OI group was significantly more negative than that in the CI group with loss feedback, while there was no significant difference between the OE and OI groups. Similarly, the P300 amplitudes following outcome feedback were larger in the CI group than that in the OI group with gain feedback and had no significant difference between OE and OI

Light absorption enhancement of black carbon in urban Beijing in summer

The light absorption enhancement (E-abs) of black carbon (BC) caused by non-BC materials is an important source of uncertainty in radiative forcing estimate, yet remains poorly understood in relatively polluted environment such as the megacity Beijing. Here BC absorption enhancement at 630 nm was in-situ measured using a ther-modenuder coupled with a soot particle aerosol mass spectrometer and a single scattering albedo monitor in Beijing in summer. The project average (+/- 1 sigma) E-abs was 1.59 ( +/- 0.26), suggesting a significant amplification of BC absorption due to coating materials. E-abs presented a clear daytime increase due to enhanced photochemical processing, and a strong dependence on the mass ratios of non-BC coatings to BC (R-BC). Our results showed that the increase in E(abs )as a function of R-BC was mainly caused by the increased contributions of secondary aerosol. Further analysis showed that the BC absorption enhancement in summer in Beijing was mainly associated with secondary formation of nitrate, sulfate and highly oxidized secondary organic aerosol (SOA), while the formation of freshly and less oxidized SOA appeared not to play an important role.Peer reviewe

Efficacité de biofilms de bactéries As-oxydantes pour l'étape de traitement biologique d'eaux potabilisables arséniées

L'arsenic est un métalloïde toxique dont la présence, relativement fréquente, dans les eaux et les sols est liée soit au fond géochimique, soit aux activités humaines. En ce qui concerne les eaux destinées à la consommation, la législation impose une concentration maximale en arsenic de 10 µg.L-1. Les effets nocifs de l'arsenic sur la santé humaine rendent nécessaire le développement de technologies efficaces et peu couteuse pour éliminer cet élément des eaux potables, ainsi que dans les aquifères pollués et dans les effluents miniers (Wang et Zhao, 2009). Une unité de traitement biologique d'eaux potabilisable faiblement arséniée (As< 50µg/L), couplée à une unité de piégeage de l'As en sortie du bioréacteur, a été mise en œuvre sur un site réel afin d'étudier la robustesse du bioprocédé. Un bioréacteur contenant de la pouzzolane (matériau utilisé dans les traitements d'eaux) a été préalablement ensemencé par une souche bactérienne As(III) oxydante autotrophe (Thiomonas arsenivorans) (Battaglia-Brunet et al., 2002, Michon et al., 2010 ; Wan et al., 2010) puis alimenté par l'eau issue du forage à température ambiante (15-17°C) avec un fonctionnement discontinu (asservissement de l'alimentation du bioréacteur à la pompe du forage d'alimentation en eau). Le suivi du développement du biofilm As(III) oxydant au cours du traitement biologique a été réalisé par la recherche des gènes codant pour l'ARNr 16S (diversité bactérienne totale) et ceux codant pour une arsénite oxydase (aoxB) (diversité des bactéries As(III)-oxydantes). Ce suivi a montré une colonisation rapide et stable du support minéral par des bactéries endogènes de l'eau à traiter. Le rendement d'oxydation de l'étape d'oxydation biologique est compris entre 54 et 100 % avec des temps de séjour de 30 minutes à 7 minutes qui sont comparables à des temps de séjour de techniques classiques de traitement. Les concentrations résiduelles en As en sortie du procédé complet (oxydation biologique + piégeage) sont inférieures à 1 µg/L, et qui sont donc très encourageants pour une application industrielle

An emerging recombinant human enterovirus 71 responsible for the 2008 outbreak of Hand Foot and Mouth Disease in Fuyang city of China

Hand, foot and mouth disease (HFMD), a common contagious disease that usually affects children, is normally mild but can have life-threatening manifestations. It can be caused by enteroviruses, particularly Coxsackieviruses and human enterovirus 71 (HEV71) with highly variable clinical manifestations. In the spring of 2008, a large, unprecedented HFMD outbreak in Fuyang city of Anhui province in the central part of southeastern China resulted in a high aggregation of fatal cases. In this study, epidemiologic and clinical investigations, laboratory testing, and genetic analyses were performed to identify the causal pathogen of the outbreak. Of the 6,049 cases reported between 1 March and 9 May of 2008, 3023 (50%) were hospitalized, 353 (5.8%) were severe and 22 (0.36%) were fatal. HEV71 was confirmed as the etiological pathogen of the outbreak. Phylogenetic analyses of entire VP1 capsid protein sequence of 45 Fuyang HEV71 isolates showed that they belong to C4a cluster of the C4 subgenotype. In addition, genetic recombinations were found in the 3D region (RNA-dependent RNA polymerase, a major component of the viral replication complex of the genome) between the Fuyang HEV71 strain and Coxsackievirus A16 (CV-A16), resulting in a recombination virus. In conclusion, an emerging recombinant HEV71 was responsible for the HFMD outbreak in Fuyang City of China, 2008

Flux regulation through glycolysis and respiration is balanced by inositol pyrophosphates in yeast

Although many prokaryotes have glycolysis alternatives, it\u27s considered as the only energy-generating glucose catabolic pathway in eukaryotes. Here, we managed to create a hybrid-glycolysis yeast. Subsequently, we identified an inositol pyrophosphatase encoded by OCA5 that could regulate glycolysis and respiration by adjusting 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP7) levels. 5-InsP7 levels could regulate the expression of genes involved in glycolysis and respiration, representing a global mechanism that could sense ATP levels and regulate central carbon metabolism. The hybrid-glycolysis yeast did not produce ethanol during growth under excess glucose and could produce 2.68 g/L free fatty acids, which is the highest reported production in shake flask of Saccharomyces cerevisiae. This study demonstrated the significance of hybrid-glycolysis yeast and determined Oca5 as an inositol pyrophosphatase controlling the balance between glycolysis and respiration, which may shed light on the role of inositol pyrophosphates in regulating eukaryotic metabolism

Identifying a few foot-and-mouth disease virus signature nucleotide strings for computational genotyping

<p>Abstract</p> <p>Background</p> <p>Serotypes of the Foot-and-Mouth disease viruses (FMDVs) were generally determined by biological experiments. The computational genotyping is not well studied even with the availability of whole viral genomes, due to uneven evolution among genes as well as frequent genetic recombination. Naively using sequence comparison for genotyping is only able to achieve a limited extent of success.</p> <p>Results</p> <p>We used 129 FMDV strains with known serotype as training strains to select as many as 140 most serotype-specific nucleotide strings. We then constructed a linear-kernel Support Vector Machine classifier using these 140 strings. Under the leave-one-out cross validation scheme, this classifier was able to assign correct serotype to 127 of these 129 strains, achieving 98.45% accuracy. It also assigned serotype correctly to an independent test set of 83 other FMDV strains downloaded separately from NCBI GenBank.</p> <p>Conclusion</p> <p>Computational genotyping is much faster and much cheaper than the wet-lab based biological experiments, upon the availability of the detailed molecular sequences. The high accuracy of our proposed method suggests the potential of utilizing a few signature nucleotide strings instead of whole genomes to determine the serotypes of novel FMDV strains.</p

Record thermopower found in an IrMn-based spintronic stack

The Seebeck effect converts thermal gradients into electricity. As an approach to power technologies in the current Internet-of-Things era, on-chip energy harvesting is highly attractive, and to be effective, demands thin film materials with large Seebeck coefficients. In spintronics, the antiferromagnetic metal IrMn has been used as the pinning layer in magnetic tunnel junctions that form building blocks for magnetic random access memories and magnetic sensors. Spin pumping experiments revealed that IrMn Néel temperature is thickness-dependent and approaches room temperature when the layer is thin. Here, we report that the Seebeck coefficient is maximum at the Néel temperature of IrMn of 0.6 to 4.0 nm in thickness in IrMn-based half magnetic tunnel junctions. We obtain a record Seebeck coefficient 390 (±10) μV K-1 at room temperature. Our results demonstrate that IrMn-based magnetic devices could harvest the heat dissipation for magnetic sensors, thus contributing to the Power-of-Things paradigm