Formation des ions bromate dans une colonne à bulles: Effets du peroxyde d'hydrogène lors de l'ozonation

L'utilisation de l'ozone, aujourd'hui très répandue dans les filières de potabilisation, n'est pas sans effet secondaire. De nombreux sous-produits peuvent se former comme notamment les ions bromates, sous produits finaux d'oxydation des bromures contenus dans les eaux. Malheureusement, le mécanisme de production de cette espèce est complexe et dépend de nombreux paramètres difficiles à appréhender.Sur une installation pilote de type colonne à bulles fonctionnant à contre-courant, nous avons étudié l'influence de différents paramètres, comme le pH, le temps de contact, la dose d'ozone et la dose de peroxyde d'hydrogène, sur la formation des bromates et la dégradation des pesticides, représentée par l'atrazine.Les résultats de la littérature ont été confirmés lors de l'emploi unique de l'ozone. La formation des ions bromate est influencée par la présence du peroxyde d'hydrogène. Cet oxydant intervient de manière non négligeable sur la consommation des entités intermédiaires. Le couple HOBr/OBr- peut être oxydé par l'ozone moléculaire et le radical OH° mais peut également être réduit par l'ozone et par le peroxyde sous sa forme acide ou sa base conjuguée. En ce qui concerne la dégradation des pesticides, l'utilisation de peroxyde d'hydrogène couplé à l'ozone favorise l'oxydation de la molécule d'atrazine grâce à la présence plus importante de radicaux hydroxyles.Une pollution accidentelle en pesticides pourra être traitée par l'ajout ponctuel de peroxyde d'hydrogène avec une augmentation de pH, la formation des bromates sera, dans ce cas, faible. La désinfection sera alors assurée par l'étape de chloration.In drinking water treatment plants, ozonation is often used to disinfect, to remove micropollutants and to improve water taste and odour. Ozonation increases organic matter biodegradability before filtration through granular active carbon and reduces the concentration of haloform precursors that react in the final chlorination step. However, by-products that could be detrimental to human health could be formed. For example, bromates, which are classified as carcinogenic compounds by the I.A.R.C, are produced during the ozonation of bromide-containing water. The mechanism of bromate formation is complex, due to the participation of molecular ozone and radical (hydroxyl and carbonate) reactions. The optimisation of the process should allow for a good disinfection and a reduction in the levels of micropollutants, together with low by-product formation.Using a pilot-scale counter-current bubble column, we have measured the bromate concentration in relation to pesticide removal. Water spiked with bromide and atrazine was stored in a completely stirred-tank (2 m3) before being pumped to the top of the column. The inlet gaseous ozone was measured by an analyser using UV detection, the outlet gaseous ozone was monitored by the potassium iodide method, and the dissolved ozone concentration was determined by the indigo trisulfonate method. Bromides and bromates were quantified by ion chromatography with a conductimetric detector, with a sodium carbonate solution as the eluant. Samples for bromate analysis were pretreated by OnGuard-Ag and OnGuard-H cartridges in series before injection. Atrazine degradation was measured by high performance liquid chromatography with a diode array detector, with a CH3CN/H2O mixture as the eluant. The linearisation of atrazine removal allowed us to calculate the hydroxyl radical concentration in a series of a completely-stirred tank reactors and in a plug-flow reactor.We have studied the influence of several parameters on bromate formation, including pH, bromide concentration and hydrogen peroxide concentration. As bromate production is a function of bromide concentration, we have chosen to calculate the ratio between the real bromate concentration and the theoretical bromate concentration if all bromide were oxidised to bromate. The pH affects bromate formation: an increase in pH in the absence of hydrogen peroxide increases bromate production, but when this oxidant is applied bromate production decreases when the pH increases. If reaction progress is represented as a function of [O3]*TC, we note that the presence of hydrogen peroxide increases bromate formation because of the increase in hydroxyl radical concentration, which favours radical formation. Nevertheless, if we represent reaction progress as a function of [OH∘]*TC, hydrogen peroxide seems to be an initiator and a scavenger in the mechanism of bromate formation. If we calculate the rates of all the oxidation and reduction reactions for HOBr/OBr- species, the contribution to the reduction of HOBr/OBr- species by peroxide is very important in comparison to the oxidation reactions, which inhibits bromate production. Without the hydrogen peroxide, the contribution of oxidation is equal to that of the reduction reaction, and in this case bromate formation is effective. When, under the same initial operational conditions, we apply hydrogen peroxide with an increase in pH, we observe a decrease in bromate formation with a decrease of the dissolved ozone concentration, which hinders the desired disinfection. The main contribution to atrazine oxidation is from the free-radical reactions, which explains why removal is better when we apply hydrogen peroxide than when we use ozone alone. However, if we want to respect a low bromate level in drinking water, atrazine degradation should not be greater than 90% for the operational conditions on our pilot-scale.If an accidental high pesticide concentration is observed, an addition of hydrogen peroxide with a concurrent increase of pH, could treat the pollution. In this case, a subsequent chlorination step would then have to be used to assure the disinfection alone

Early Effect Markers and Exposure Determinants of Metalworking Fluids Among Metal Industry Workers: Protocol for a Field Study.

Exposure to aerosols from metalworking fluids (MWF) has previously been related to a series of adverse health outcomes (eg, cancer, respiratory diseases). Our present epidemiological study focuses on occupational exposures to MWF and a panel of exposure and effect biomarkers. We hypothesize that these health outcomes are caused by particle exposure that generates oxidative stress, leading to airway inflammation and ultimately to chronic respiratory diseases. We aimed to assess whether MWF exposure, in particular as characterized by its oxidative potential, is associated with biomarkers of oxidative stress and inflammation as well as genotoxic effects. The ultimate goal is to develop exposure reduction strategies based on exposure determinants that best predict MWF-related health outcomes. The following relationships will be explored: (1) exposure determinants and measured exposure; (2) occupational exposure and preclinical and clinical effect markers; (3) exposure biomarkers and biomarkers of effect in both exhaled breath condensate and urine; and (4) biomarkers of effect, genotoxic effects and respiratory symptoms. At least 90 workers from France and Switzerland (30 controls, 30 exposed to straight MWF and 30 to aqueous MWF) were followed over three consecutive days after a nonexposed period of at least two days. The exposure assessment is based on MWF, metal, aldehyde, and ultrafine particle number concentrations, as well as the intrinsic oxidative potential of aerosols. Furthermore, exposure biomarkers such as metals, metabolites of polycyclic aromatic hydrocarbons and nitrosamine are measured in exhaled breath condensate and urine. Oxidative stress biomarkers (malondialdehyde, 8-isoprostane, 8-hydroxy-2'-deoxyguanosine, nitrates, and nitrites) and exhaled nitric oxide, an airway inflammation marker, are repeatedly measured in exhaled breath condensate and urine. Genotoxic effects are assessed using the buccal micronucleus cytome assay. The statistical analyses will include modelling exposure as a function of exposure determinants, modelling the evolution of the biomarkers of exposure and effect as a function of the measured exposure, and modelling respiratory symptoms and genotoxic effects as a function of the assessed long-term exposure. Data collection, which occurred from January 2018 until June 2019, included 20 companies. At the date of writing, the study included 100 subjects and 29 nonoccupationally exposed controls. This study is unique as it comprises human biological samples, questionnaires, and MWF exposure measurement. The biomarkers collected in our study are all noninvasive and are useful in monitoring MWF exposed workers. The aim is to develop preventative strategies based on exposure determinants related to health outcomes. DERR1-10.2196/13744

Automatic 3D Boresight and Latency Estimation of IMU and Multi-Beam Echo Sounder Systems

International audienceThis paper present some methods for automatic boresight and latency calibration for Multi Beam Echo Sounders and Inertial Measurement Units. The approach is based on the analysis of overlapping data and the resolution of surface matching problems. Surface patches and data are selected in order to guarantee the observability of the effet of boresight and latency. These methods are intended to replace the classical patch-test by full automatic 3D calibration methods

Oxidative potential of aerosolized metalworking fluids in occupational settings.

The oxidative potential (OP) measures the ability of pollutants to oxidize a chemical/biological probe. Such assays are starting to gain acceptance as integrative exposure metrics associated with inflammatory-based pathologies. Diseases such as asthma, rhinitis or cancers are reported for workers exposed to oil mist, which are aerosols of metal working fluids (MWF) emitted during the machining of metals. Measuring oil mist in the air is challenging, and exposures are often quantified as the mass fraction, which does not account for exposures to the gaseous fraction. Consequently, exposures are underestimated and furthermore, the hazardous property of oil mist is not assessed. We postulate that it is more relevant to assess occupational exposures to the hazardous fractions of oil mist by measuring OP than by simply measuring mass. We characterized exposures to straight and water-based MWF among workers in the French and Swiss mechanical industry using standard methods for oil mist and the ferrous orange xylenol assay for OP assessment (OP <sup>FOX</sup> ). Considering the particulate fraction, the water-based MWF presented the greatest OP <sup>FOX</sup> . The OP was associated with organic carbon and iron content. The gaseous fraction of the oil mist presented also an important redox activity, particularly in workshops where straight oils were used. The hexanal concentration was associated with this OP <sup>FOX</sup> . The OP <sup>FOX</sup> measurement is thus integrative of multiple parameters, and bring complementary information when assessing MWF exposures. Our results highlight that OP <sup>FOX</sup> account for MWF type and could be an interesting parameter to characterize such exposure