Investigation of Stormwater BMP Water Quality Performance Characteristics with Respect to Storm Event Variables and Influent Event Mean Concentrations

Stormwater is known to be a major source of water pollution. In addition to increased flows resulting from increased impervious area in watersheds, stormwater is known to carry pollutants such a suspended solids, hydrocarbons, and nutrients into receiving water bodies. Because of this, stormwater treatment systems, referred to as ‘best management practices’ (BMPs), are utilized to dampen peak flows, reduce total runoff volume, and remove pollutants. While many studies have investigated the effectiveness of various BMPs in the removal of pollutants, fewer studies have investigated the effects of numerous storm variables on the effectiveness of treatment systems. This thesis investigates the effects of storm event variables on the removal efficiencies of different BMPs for different stormwater pollutants, with the goal of drawing broader conclusions on the effects of event variables on system performance.Using data from the University of New Hampshire Stormwater Center (UNHSC) and International Stormwater BMP Database, this thesis investigated the effects of variables such as event duration, precipitation depth, runoff volume, peak rain intensity, peak runoff flow, and the antecedent dry period on the percent removal (%RE) of pollutants such as solids, hydrocarbons, Nitrogen, Zinc and Phosphorus in BMPs such as bioretention systems, swales, retention ponds, subsurface gravel wetlands, and sand filters. Apart from investigating these specific relationships, these analyses were conducted to evaluate if event variables can serve as adequate indicators of BMP performance. Using statistical analysis techniques including regression analysis and principal component analysis, this study investigates relationships between storm event variables, influent event mean concentrations (EMCs), and removal rates across different pollutants and BMPs. Most relationships were not determined to be statistically significant at the 95% confidence level. Although few relationships were significant at the 95% confidence level, there were additional relationships found to be significant at lower levels of confidence. A trend of note was a group of positive relationships between several influent EMCs and removal rates. It is worth noting that antecedent dry period had no statistical bearing on the influent concentration and removal efficiency, when it is has been found by previous studies to effect pollutant loadings. This lack of bearing would be expected because of the use of EMCs masking first flush characteristics. These analyses were also used to examine the proportions of relationships effecting removal rates by system. These results indicated swales were these systems whose performance was most effected by changes in event variables, followed by sand filters, bioretention systems and subsurface gravel wetlands, and retention ponds being he east effected. Although analysis yielded a number of statistically significant trends indicating relationships effecting system performance, the results suggest that relationships effecting system performance are either not of sufficient statistical confidence, or are a result of additional intervening factors effecting performance. This indicates that hydrologic factors are not a sufficient indicator or predictor of system performance. Overall, these results substantiate performance in Green Stormwater Infrastructure (GSI) to be mostly independent of event variables because of the use of static design and regulated outflow. This backs up that GSI static design standards are adequate for the removal of the pollutants studied

Les Probabilités Défaillance comme Indicateurs de Performance des Barrières Techniques de Sécurité - Approche Analytique

International audienceFrench environmental laws require industrialists to include probability criteria in risk assessments, especially to define confidence levels for risk management measures. This paper presents the failure probabilities as efficient indicators for technical safety barrier performances. Generic formulas are proposed to evaluate these probabilities, including failure rate, barrier architecture, full and partial proof tests. In many cases, these results can be directly used to assess safety barrier confidence levels

Allocation de SIL requis sur un réseau de refroidissement à l'ammoniac conformément à la norme CEI 61511

International audienceThe IEC 61511 standard addresses to safety in the application of safety instrumented systems for the Process Industries. The standard requires to carry out process hazard and risk assessment in order to deduce specifications for the SIS. Two main concepts, fundamental to its application, are underlined : safety lifecycle and safety integrity levels. This article deals more with the safety integrity levels (SIL) and to their allocation depending on the SIS considered. This international standard. describes various quantitative and qualitative methodology for SIL (Safety Integrity Level) allocation. The choice for one or another methodology will depend on various criteria as illustrated in this paper. The paper make a brief description of three spreaded methods in the Process Industries. The selection criteria for each method are presented. Advantages and disadvantages of these various methods are indicated. In order to illustrate the methodology of a SIL allocation, a case study on a storage unit of ammonia is presentedLa norme CEI 61511 s'intéresse à la sécurité fonctionnelle dans l'application des systèmes instrumentés de sécurité aux industries de production par processus. Elle exige dans ce cadre de conduire une évaluation de danger et de risque des processus pour permettre d'en déduire des spécifications pour les SIS. Deux concepts fondamentaux sont mis en avant : le cycle de vie de sécurité et les niveaux d'intégrité de sécurité. Cet article s'intéresse plus particulièrement au niveaux d'intégrité de sécurité (SIL) et à leur allocation en fonction du SIS à évaluer. La norme décrit différentes méthodes d'allocation de SIL (Safety Integrity Level), qu'elles soient qualitatives ou quantitatives. Aucune méthode n'est à privilégier, le choix d'une technique dépendra de différents critères. Cet article fait ainsi une brève description de trois méthodes répandues dans le secteur des industries de procédés. Nous présentons les critères qui orientent le choix d'une méthode et indiquons les avantages et les inconvénients de ces différentes méthodes. Afin d'expliciter le déroulement d'une démarche d'allocation de SIL, une application sur une unité de stockage d'ammoniac est présenté

Taux de défaillance bayésien pondéré à partir de données de retour d'expérience

International audienceFrom now on, it is necessary to evaluate probabilistically the materials's operation safety in order to achieve a safety analyse. The essential failure rates for those kind of studies can be recovered thanks to reliability database. The interest is undeniable but the use is made difficult due to differences encountered in the data from one source to the other. This article propose a method to improve the taking into account of the data resulting from various sources. The study use Bayesian statistics with an innovating aspect in the entering data weighting in particular by introducing Fischer's information quantity.Afin de réaliser une étude de sécurité, il est désormais nécessaire d'évaluer de manière probabiliste la sûreté de fonctionnement des matériels. Les taux de défaillance indispensables pour ces études peuvent s'obtenir à partir des bases de données. L'intérêt de ces bases est indéniable mais leur utilisation est rendue difficile par les différences de valeurs trouvées dans celles-ci. Cet article propose une méthode pour améliorer la prise en compte des données issues de différentes sources. La démarche utilise les techniques bayésiennes avec un aspect innovant dans la pondération des données d'entrées notamment par la quantité d'information de Fischer

Limites d'utilisation des normes EN 61508 - EN 61511. Retour d'expérience d'un organisme de certification

National audienceSafety functional standards and in particular the standards IEC 61508/61511 introduce an assessment of the dangerous failure probability on demand in complement of the traditional deterministic analysis. The application of these standards on various equipments and systems made it possible to highlight difficulties relating to the concepts calculated thus to the associated mathematical tools. Comparison of various mathematical models highlights that the use of Markov graphs can lead to approximate results for partially reparable equipments. The article will try to bring brief replies to these difficulties while being based on the experiment of INERIS in the assessment and the certification of instrumented safety material and systems.Les normes de sécurité fonctionnelle et notamment les normes EN 61508/61511 introduisent une évaluation de la probabilité de défaillances dangereuses en complément de l'analyse déterministe traditionnelle. L'application de ces normes sur différents matériels et systèmes a permis de mettre en évidence des difficultés relatives à la nature des grandeurs calculées ainsi qu'aux outils mathématiques associés. La comparaison des différents modèles mathématiques met en évidence que l'utilisation de graphes de Markov peut conduire à des résultats approximatifs pour des matériels partiellement réparables. L'article tentera d'apporter des éléments de réponse à ces difficultés en s'appuyant sur l'expérience de l'INERIS dans l'évaluation et la certification de matériel et de systèmes instrumentés de sécurité

Modélisation des taux de défaillance en mécanique - Combinaison d'une loi de Weibull et d'un modèle de Cox pour la modélisation des taux de défaillance en fonction du temps et des facteurs d'influence

International audienceLa fiabilité des matériels mécaniques est largement conditionnée par les caractéristiques propres à chaque système, à ses conditions d'utilisation, son environnement... De plus, les mécanismes de dégradations comme la fatigue et le stress créent des phénomènes de vieillissement. Les bases de données de fiabilité, en fournissant des taux de défaillance génériques et constants, ne permettent pas de prendre en considération ces particularités. L'utilisation de telles bases entraîne par conséquent de grandes incertitudes quant aux résultats des évaluations fiabilistes. Nous proposons dans cet article une modélisation des taux de défaillance, fonction du temps, qui prend en compte les facteurs d'influence. Une application permet de valider le modèle

Mise en conformité CE d'un système préventif de déclenchement d'avalanche

National audienc

Kit receptor tyrosine kinase dysregulations in feline splenic mast cell tumours

This study investigated Ki t receptor dysregulations (cytoplasmic immunohistochemical expression and/or c-KIT mutations) in cats a\ufb00ected with splenic mast cell tumours. Twenty-two cats were included. Median survival time was 780 days (range: 1\u20131219). An exclusive splenic involvement was signi\ufb01cantly (P = 0.042) associated with longer survival (807 versus 120 days). Eighteen tumours (85.7%) showed Kit cytoplasmic expression (Kit pattern 2, 3). Mutation analysis was successful in 20 cases. Fourteen missense mutations were detected in 13 out of 20 tumours (65%). Eleven (78.6%) were located in exon 8, and three (21.6%) in exon 9. No mutations were detected in exons 11 and 17. Seven mutations corresponded to the same internal tandem duplication in exon 8 (c.1245_1256dup). Although the association between Kit cytoplasmic expression and mutations was signi\ufb01cant, immunohistochemistry cannot be considered a surrogate marker for mutation analysis. No correlation was observed between c-Kit mutations and tumour di\ufb00erentiation, mitotic activity or survival

Recent advances in the understanding and management of mucormycosis [version 1; referees: 2 approved]

Mucormycoses were difficult-to-manage infections owing to limited diagnostic tools and therapeutic options. We review here advances in pathology understanding, diagnostic tools including computed tomography, and serum polymerase chain reaction and therapeutic options