WET SCRUBBING INTENSIFICATION APPLIED TO HYDROGEN SULPHIDE REMOVAL IN WASTE WATER TREATMENT PLANT

International audienceHydrogen sulphide removal in a Waste Water Treatment Plant at semi-industrial scale in a compact wet scrubber has been investigated. The gas residence time in the scrubber was reduced to 30 ms using a NaOCl caustic scrubbing solution. The contactor is composed of a wire mesh packing structure where liquid and gas flow co-currently at high velocity (> 12 m.s-1). H2S removal percentages higher than 95% could be achieved whereas a moderate pressure drop was measured (< 4000 Pa). Both the hydrodynamic and chemical conditions can influence the efficiency of the process. Correlations were developed to predict both the pressure drop and the H2S removal efficiency at given operating conditions

Traitement de composés organiques volatils par lavage chimique compact: recyclage de la solution de lavage par oxydation avancée O3/H2O2

National audienceThis study focuses on Volatile Organic Compounds (VOC) treatment in a compact chemical scrubber composed of a structured packing operating at co-current and high gas superficial velocity (> 10 m.s-1). The scrubbing liquid is composed of ozone and hydrogen peroxide to generate very reactive hydroxyl radicals. Results demonstrate a high mineralisation rate of the transferred VOC, even with low oxidant concentrations. Therefore, the scrubbing liquid can be recycled and recirculated at the top of the scrubber without efficiency drop over time. Neutral VOC removal efficiency increases with their solubility in water, from 14% for dimethyldisulfide to 86% for butanol using a mass flow rates ratio (L/G) of 2.5 and residence time of 20 ms. For trimethylamine, a basic VOC, the increased apparent solubility at pH = 8 leads to a high removal efficiency of 80%. Major by-products were identified and quantified. An absence of stripping in the treated gas emphasizes their innocuity.Cette étude porte sur le traitement de Composés Organiques Volatils (COV) dans un laveur chimique compact composé d’un garnissage structuré fonctionnant à co-courant et à vitesse superficielle du gaz élevée (> 10 m.s-1). La solution aqueuse de lavage se compose d’un mélange d’ozone et de peroxyde d’hydrogène afin de générer des radicaux hydroxyles très réactifs. Les résultats démontrent une minéralisation poussée des COV transférés même avec des concentrations en oxydants modestes. La solution de lavage peut donc être régénérée et réinjectée en tête du laveur sans diminution d’efficacité au cours du temps. L’abattement en phase gazeuse des COV neutres, observés pour un rapport des débits massiques L/G de 2,5, augmente avec leur solubilité en phase aqueuse, démarrant à 14% pour le dimethyldisulfide jusqu’à 86% pour le butanol en 20 ms de temps de contact. Pour la triméthylamine, composé basique, l’augmentation de la solubilité apparente à pH 8 permet d’atteindre un abattement élevé de 80%. Les sous-produits majoritaires ont été identifiés et quantifiés. L’absence de stripping dans le gaz traité met en évidence leur innocuité

Hydrogen sulphide removal in waste water treatment plant by compact oxidative scrubbing in Aquilair PlusTM process

International audienceRecently, the development of a high voidage contactor, named Aquilair Plus™, has demonstrated high efficiency for chemical scrubbing of hydrogen sulphide. Liquid and gas phases flow at co-current and high velocity, leading to a great dispersion of the liquid and then to an enhancement of the mass transfer rate by comparison with classical packed towers. This study focused on the results which obtained at semi-industrial scale with the Aquilair PlusTM process on a waste water treatment plant located in France. The scrubbing liquid consisted of a sodium hypochlorite alkaline solution. At once, pressure drop, H2S removal and reagents consumption were followed. The influence of the superficial gas velocity, liquid-to-gas mass ratio (L/G), pH, hypochlorite concentration of the scrubbing liquid and H2S inlet concentration was characterised. H2S removal percentages higher than 90% could be easily achieved with a moderate pressure drop (< 40 mbar). Both hydrodynamic and chemical conditions proved to influence performances. Reagents consumptions slightly higher than the predicted ones were measured

Incomplete tricarboxylic acid cycle and proton gradient in Pandoravirus massiliensis: is it still a virus?

The discovery of Acanthamoeba polyphaga Mimivirus, the first isolated giant virus of amoeba, challenged the historical hallmarks defining a virus. Giant virion sizes are known to reach up to 2.3µm, making them visible by optical microscopy. Their large genome sizes of up to 2.5Mb can encode proteins involved in the translation apparatus. We have investigated possible energy production in Pandoravirus massiliensis. Mitochondrial membrane markers allowed for the detection of a membrane potential in purified virions and this was enhanced by a regulator of the tricarboxylic acid cycle but abolished by the use of a depolarizing agent. Bioinformatics was employed to identify enzymes involved in virion proton gradient generation and this approach revealed that 8 putative P. massiliensis proteins exhibited low sequence identities with known cellular enzymes involved in the universal tricarboxylic acid cycle. Further, all 8 viral genes were transcribed during replication. The product of one of these genes, ORF132, was cloned and expressed in Escherichia coli, and shown to function as an isocitrate dehydrogenase, a key enzyme of the tricarboxylic acid cycle. Our findings show for the first time that a membrane potential can exist in Pandoraviruses, and this may be related to tricarboxylic acid cycle. The presence of a proton gradient in P. massiliensis makes this virus a form of life for which it is legitimate to ask the question ‘what is a virus?’

Green Edge ice camp campaigns : understanding the processes controlling the under-ice Arctic phytoplankton spring bloom

The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Qikiqtarjuaq Island in Baffin Bay (67.4797∘ N, 63.7895∘ W). During both expeditions, a large suite of physical, chemical and biological variables was measured beneath a consolidated sea-ice cover from the surface to the bottom (at 360 m depth) to better understand the factors driving the PSB. Key variables, such as conservative temperature, absolute salinity, radiance, irradiance, nutrient concentrations, chlorophyll a concentration, bacteria, phytoplankton and zooplankton abundance and taxonomy, and carbon stocks and fluxes were routinely measured at the ice camp. Meteorological and snow-relevant variables were also monitored. Here, we present the results of a joint effort to tidy and standardize the collected datasets, which will facilitate their reuse in other Arctic studies

Room-temperature single-phase Li insertion/extraction in nanoscale LixFePO4

Classical electrodes for Li-ion technology operate by either single-phase or two-phase Li insertion/de-insertion processes, with single-phase mechanisms presenting some intrinsic advantages with respect to various storage applications. We report the feasibility to drive the well-established two-phase room-temperature insertion process in LiFePO4 electrodes into a single-phase one by modifying the material's particle size and ion ordering. Electrodes made of LiFePO4 nanoparticles (40 nm) formed by a low-temperature precipitation process exhibit sloping voltage charge/discharge curves, characteristic of a single-phase behaviour. The presence of defects and cation vacancies, as deduced by chemical/physical analytical techniques, is crucial in accounting for our results. Whereas the interdependency of particle size, composition and structure complicate the theorists' attempts to model phase stability in nanoscale materials, it provides new opportunities for chemists and electrochemists because numerous electrode materials could exhibit a similar behaviour at the nanoscale once their syntheses have been correctly worked out

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century