Biolixiviation des métaux lourds et stabilisation des boues municipales: effet de la forme du souffre élémentaire utilisé comme substrat

La présence de concentrations élevées en métaux lourds retrouvés dans les boues de stations d'épuration est un facteur important limitant ainsi leurs différents modes de dispositions (rejet en mer, enfouissement, incinération, ou même recyclage comme fertilisant agricole ou forestier) par crainte de dégâts considérables qui pourraient être causés à l'environnement. L'objectif de ce travail consistait à mettre au point un procédé qui permettrait conjointement la stabilisation des boues municipales et l'enlèvement des métaux lourds qui y sont associés. L'approche poursuivie dans cette étude était de vérifier si ce procédé microbien, conçu pour enlever les métaux lourds associés aux boues municipales, pourrait éventuellement remplacer les procédés conventionnels de stabilisation des boues municipales, ce qui réduirait considérablement les temps et coûts de traitement. Ce procédé microbien consiste à utiliser des souches de thiobacilles qui oxydent le soufre élémentaire, produisant ainsi de l'acide sulfurique, et par la même occasion une forte baisse de pH (1.5). Les résultats obtenus en cultures discontinues, en bioréacteurs, avec des boues primaires provenant de la station d'épuration de la Communauté Urbaine de Québec (C.U.Q.- Est) montrent que cette chute de pH entraîne une solubilisation importante des métaux (Cr: 56 %, Cu: 97 %, Fe: 30 à 40 %, Pb: 69 %, Zn: 98 % ), du phosphore (52 %), ainsi qu'une réduction appréciable des matières volatiles en suspension (40 à 50 % ), et ce, après seulement 7 jours de traitement. Le soufre nécessaire à la biolixiviation- stabilisation est introduit, dans le cas de notre étude, sous forme de granules ou de blocs. Ce choix de la forme de soufre influe beaucoup sur la qualité de la boue produite, ainsi que sur son pouvoir acidophile après neutralisation. Le soufre en blocs s'avère plus efficace et aussi préférable au soufre en granules quant au pouvoir acidophile, après neutralisation, de la boue produite.Given the potential geochemical mobility and recognizd toxicity of heavy metals, their presence at high concentrations in sewage sludges imposes serious limitations on various sludge disposal practices (ocean disposal, landfill, incineration, or use as a fertilizer in agriculture or forestry), The objectve of this work was to develop a process that would permit the simultaneous stabilization of sewage sludges and the removal of heavy metals associated with them. The approach followed was to verify if this microbial leaching procedure could eventually replace conventional sludge stabilization processes and hence considerably reduce the time and cost of treatment. The microbial process consists of using thiobacillus strains which, in the presence of air, oxidize elemental sulfur to sulfuric acid, thus reducing the pH to very acidic levels (pH 1.5). This biological oxidation of elemental sulfur is brought about by two groups of sulfur-oxidizing bacteria, the less-acidophilic and the acidophilic thiobacilli. The initial acid production and pH reduction is due to the less-acidophilic bactena (Thiobacillus thioparus) which lower the pH to about 4.0. This is followed by the growth of acidophilic bacteria (Thiobacillus thiooxidans) and fruther pH reduction.Batch culture experiments were carried out in 30 L and 8 L reactors with primary sludges obtained from the Quebec urban community's wastewater treatment centre. Elemental sulfur and inoculum were added at the beginning of each experiment The inoculum was prepared by adding 1 % tyndalized sulfur powder to fresh secondary sludge and incubating for 8 days (final pH 1.5 to 2.0). A small portion (5 %) of this acidified sludge was then used as an inoculum for another batch of fresh sludge and this process was repeated several times until an acclimatized inoculum was obtained which could oxidize elemental sulfur rapidly, without an appreciable lag phase. The elemental sulfur necessary as substrate for the simultaneous bioleaching and sludge stabilization was introduced in the form of granules (2.4 to 4 mm diameter) or blocks (25 mm diameter).Sludge pH and ORP were measured at 24 hour intervals and all other measurements were carried out at 48 hour intervals. The results demonstrate that the addition of elemental sulfur and inoculum resulted in a considerable lowering of the sludge pH during the incubation period. Such pH lowering was not observed in cultures to which sulfur and inoculum were not added. This lowering of pH (2.1) was related to the quantity of substrate (sulfur) and inoculum present in the medium. An increase in the medium ORP (from -50 to about 500 mV) was also observed. Acidification of the medium along with the elevated ORP levels resulted in the solubilization of metals initially present in the sludge. This pH reduction, after only 7 days of treatment, effected an important metal solubilization (Cr: 56 %, Cu: 97 %, Be: 30-40 %, Pb: 69 %, Zn: 98 %), as well as an appreciable reduction in phosphorus (52 %) and in the volatile suspended solids concentration (40-50 %). In addition, the sludge which initially had a highly repulsive odour was rendered odourless.In a previous study we had showm that for an optimum rate of acidification of the sludge a minimum concentration of elemental sulfur (2 g/L) was necessary, even though only 40 % of this sulfur was oxidized. In the present experiment the physical form of the sulfur was shown to influence both the quality of sludge produced and its acid-generating capacity after neutralization. Sulfur in the form of blocks was more efficient than granules in that the elemental sulfur could be readily separated from the sludge at the end of the treatment, yielding a sludge after neutralization that had a low acid-generating capacity. In the case of granules, the unused sulfur was broken down into a fine powder during the course of the bioleaching experiment and could not be separated from the leached sludge - even after neutralization, the leached sludge exhibited a high acid-generating capacity, which would limit its use as a fertilizer on agricultural land

The Role of Mirror Dichroic in Tandem Solar Cell GaAs/Si

The good choice of the mirror dichroic between two solar cells was key to the development of the first two-terminal monolithic, multi-junction solar cell. In this paper describes a simulation for mirror dichroic between the first cell (GaAs) and second cell (Si ). In the simulation, Spectrum of the mirror Issued to first cell is changed the 0.3 ?m to0.6 ?m and the rest of the spectrum turns to the second cell. the By varying the mirror dichroic was demonstrate in the form of current-voltage(I-V) characteristics and quantum efficiency (QE). Keywords: multi-junction, mirror dichroic, quantum efficiency

Simulation of Hetero-junction (GaInP/GaAs) Solar Cell Using AMPS-1D

Photovoltaic conversion is the direct conversion of electromagnetic energy into electrical energy continuously. This electromagnetic energy is the most solar radiation. In this work we performed a computer modelling using AMPS 1D optimization of hetero-junction solar cells GaInP / GaAs configuration for p/n. We studied the influence of the thickness the base layer in the cell offers on the open circuit voltage, the short circuit current and efficiency

Eclipses observed by LYRA - a sensitive tool to test the models for the solar irradiance

We analyze the light curves of the recent solar eclipses measured by the Herzberg channel (200-220 nm) of the Large Yield RAdiometer (LYRA) onboard PROBA-2. The measurements allow us to accurately retrieve the center- to-limb variations (CLV) of the solar brightness. The formation height of the radiation depends on the observing angle so the examination of the CLV provide information about a broad range of heights in the solar atmosphere. We employ the 1D NLTE radiative transfer COde for Solar Irradiance (COSI) to model the measured light curves and corresponding CLV dependencies. The modeling is used to test and constrain the existing 1D models of the solar atmosphere, e.g. the temperature structure of the photosphere and the treatment of the pseudo- continuum opacities in the Herzberg continuum range. We show that COSI can accurately reproduce not only the irradiance from the entire solar disk, but also the measured CLV. It hence can be used as a reliable tool for modeling the variability of the spectral solar irradiance.Comment: 19 pages, 9 figures, Solar Physic

Milk exosomes: beyond dietary microRNAs

Extracellular vesicles deliver a variety of cargos to recipient cells, including the delivery of cargos in dietary vesicles from bovine milk to non-bovine species. The rate of discovery in this important line of research is slowed by a controversy whether the delivery and bioactivity of a single class of vesicle cargos, microRNAs, are real or not. This opinion paper argues that the evidence in support of the bioavailability of microRNAs encapsulated in dietary exosomes outweighs the evidence produced by scholars doubting that phenomenon is real. Importantly, this paper posits that the time is ripe to look beyond microRNA cargos and pursue innovative pathways through which dietary exosomes alter metabolism. Here, we highlight potentially fruitful lines of exploration

Chemical vapour deposition synthetic diamond: materials, technology and applications

Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synthesized in planar form, however non-planar geometries are also possible and enable a number of key applications. This article reviews the material properties and characteristics of single crystal and polycrystalline CVD diamond, and how these can be utilized, focusing particularly on optics, electronics and electrochemistry. It also summarizes how CVD diamond can be tailored for specific applications, based on the ability to synthesize a consistent and engineered high performance product.Comment: 51 pages, 16 figure

Water Vapor Vertical Profiles on Mars in Dust Storms Observed by TGO/NOMAD

It has been suggested that dust storms efficiently transport water vapor from the near‐surface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to mid‐September 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162–260° and Ls = 298–345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40–100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°S‐60°N at the growth phase of the dust storm (Ls = 195°–220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°–260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two cells) to the solstitial one (a single pole‐to‐pole cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322–327°), in particular at latitudes greater than 60°S

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points