Approche pour l'identification des causes de la mauvaise décantation des solides biologiques

Les procédés d'épuration biologique à culture libre (boues activées) comprennent habituellement un décanteur qui permet de concentrer les solides biologiques en vue de leur recirculation en tête du réacteur biologique. Lorsque ce décanteur fonctionne mal on observe une perte de solides biologiques (SB), ce qui se traduit par une augmentation de la concentration des matières en suspension (MES) dans l'effluent du décanteur secondaire et par une baisse des performances du procédé d'épuration. Lorsque la concentration de MES dans l'effluent du décanteur secondaire est trop élevée on mesure l'indice de volume des boues (IVB). Un IVB faible indique que les solides biologiques ont de bonnes caractéristiques de décantation de sorte que la cause de la mauvaise efficacité du décanteur est d'ordre physique et peut être identifiée facilement. Lorsque l'IVB est élevé, la mauvaise décantation est alors causée par un désordre de l'écosystème qui se traduit le plus souvent par une croissance excessive d'organismes filamenteux. Les causes et les solutions d'un tel problème sont alors difficiles à identifier. Pour ce travail, les auteurs ont réalisé une importante revue bibliographique dont les résultats sont présentés sous la forme d'un cheminement critique (fig. 1). Dans cette figure, les cases numérotées de 1 à 48 sont liées par des énoncés logiques. Ainsi, en répondant à des questions simples, il est possible de cheminer dans la figure 1 et d'identifier les causes les plus probables du déséquilibre microbiologique ainsi que les solutions qui ont déjà été apportées avec succès. De plus les auteurs ont associé à chaque case une fiche technique (portant le même numéro que la case) sur laquelle sont présentées des explications et la liste des références consultées.Activated sludge is a microbiological aerated sewage treatment process which includes a secondary clarifier to separate the treated effluent from the biological solids. Part of the concentrated solids is recirculated to maintain an adequate concentration of mixed liquor suspended solids (MLSS) In the aerated basin. When the secondary clarifier malfunctions, some biological solids are lost to the effluent : the process efficiency drops and the concentration of suspended solids (SS) increases. When the SS in the effluent is too high the sludge volume index (SVI) must be measured. A low SVI means that the biological solids have good sedimentation characteristics : the problem is thon physical in nature and is easily identified. When the SVI is high, the problem is due to a disturbance of the microbiological ecosystem, which is at the origin of excessive filamentous organism growth. The origins and solutions of such a problem are much harder to find. To this end the authors proceeded with an important review of the literature, the results of which are summarized through a critical path, in figure 1. Files from 1 to 48 are linked by logical statements in such a way that by answering simple questions, one can proceed through the files and identify the must probable cause of the biological disturbance as well as the solution which has already proven successful. Furthermore, the authors have linked each file to a technical file which bears the same number and on which an explanation and references are found.Before proceeding with figure 1 to identify a problem in real life, one must obtain information, resulting from an analysis and observations, with regard to plant effluent, primary clarifier effluent and activated sludge characteristics, including the MLSS concentration. One must also know the chemical oxygen demand (COD), the soluble and total biochemical oxygen demand (BOD5), as well as the nitrogen and phosphorus concentrations in the plant influent. Furthermore, one must also be told of the presence of toxic material or industrial wastes in the sewage and of the fraction of pollution load which is in the form of particulates. Whether sudden changes in the quality of the plant influent have occurred is worth knowing. The concentration of oxygen or hydrogen sulfide in the primary clarifier is also important. One must also gather data related to the activated sludge treatment itself : type of reactor (completely mixed or plug flow), mixed liquor volatile suspended solids (MLVSS) concentration, dissolved oxygen concentration, rate of oxygen uptake and pH. Finally, the results of a microbiological analysis of the sludge are very useful.To illustrate the use of figure 1, let us say that we have the following data :a) Many filamentous microorganisms are present in the MLSS, in particular Microthrix parvicella, type 0092, and Thiothrix sp;b) The rate of dissolved oxygen uptake is 12 mg O2/g of SS - h;c) The rate of COD removal is 0,48 Kg/Kg of SS -d;d) There are no toxic substances in the plant influent;e) There are no abrupt changes in plant influent quality;f) The pHs of the plant influent and of the MLSS are 7,0 and 6,8 respectively;g) The ammonia nitrogen concentration of the plant influent is 1,2 mg/L (N);h) The phosphorus concentration of the plant influent is 4,4 mg/L (P);i) The total and soluble BOD5 concentrations of the plant influent are 400 and 80 mg/L respectively.With this information, we are ready to proceed through figure 1. From file one, one goes to file 2, since the rate of oxygen uptake is sufficient. Otherwise, we would have proceeded to file 32. The reactor being completely mixed, the next step is file 3, where it is said that, because of the low soluble BOD5 concentration one must go to file 9, where we find a fast of filamentous microarganisms which may be responsible for the disturbance. Since two of these microorganisms are effectively present in the mixed liquor suspended solids (MLSS), Microthrox parvicella and type 0092, we are invited to go to file 35, where it is stated that someone has already solved a similar problem by creating a modified contact zone to increase the substrats (organic matter) concentration around the microbiological flocs. The third filamentous microorganism is not identified in file 9. As a second possibility one may assume, in file 2. That the mixing is not complete, which is often the case. With the help of information and results of analyses already available, we proceed, through file 4, 14, 15 and 16, to file 20 where Thiothrixsp is included in the microorganisms listed. File 20 is linked to file 41, where it is said that the controlled addition of nitrogen in the plant influent has already been used to solve this type of problem.The critical path presented in this article is the result of an elaborate study. It may be used as a tool to identify the causes of bad biological flocs sedimentation in the secondary clarifier and select solutions that have already been used successfully

Delivering reform in English healthcare: an ideational perspective

A variety of perspectives has been put forward to understand reform across healthcare systems. Recently, some have called for these perspectives to give greater recognition to the role of ideational processes. The purpose of this article is to present an ideational approach to understanding the delivery of healthcare reform. It draws on a case of English healthcare reform – the Next Stage Review led by Lord Darzi – to show how the delivery of its reform proposals was associated with four ideational frames. These frames built on the idea of “progress” in responding to existing problems; the idea of “prevailing policy” in forming part of a bricolage of ideas within institutional contexts; the idea of “prescription” as top-down structural change at odds with local contexts; and the idea of “professional disputes” in challenging the notion of clinical engagement across professional groups. The article discusses the implications of these ideas in furthering our understanding of policy change, conflict and continuity across healthcare settings

Enhanced heterogeneously catalyzed Suzuki–Miyaura reaction over SiliaCat Pd(0)

The SiliaCat Pd(0) solid catalyst can be efficiently employed in the Suzuki–Miyaura cross-coupling of an ample variety of haloarenes, including economically viable chloroarenes. The catalyst can be extensively recycled without loss of activity and with low leaching of valued palladium, opening the route to widespread utilization of the method to afford high yields of biaryls devoid of contaminating by-products

Regulatory Constructivism: Application of Q Methodology in Italy and China

Conventional view holds that beliefs play an important role in the development of regulations but there is little evidence to support this claim. We use Comparative Q Methodology to systematically map out and compare the beliefs of public officers in China and Italy, two countries with contrasting sets of institutions but have both adopted similar ideas about integrated water resource management. We find some similarities and differences in the beliefs of public officers in both countries. In particular, we find that in both countries beliefs on the regulation of water utilities are diverse and fragmented on issues such as ownership structure of water utilities, how water infrastructure development should be funded, and how tariffs should be regulated. Our findings have two implications for theory, methods and practice. First, the Q methodology is a useful tool for systematically mapping out the beliefs of regulators and managers. Second, systematically mapping out beliefs will help facilitate the development of an alternative regime of regulation such as negotiated rule making. This alternative regime can provide substantial benefits such as more efficient rule making, more cost effective enforcement and compliance, and more equitable in terms of balancing the interests of stakeholders

The nomenclature, definition and classification of cardiac structures in the setting of heterotaxy

AbstractIn 2000, The International Nomenclature Committee for Pediatric and Congenital Heart Disease was established. This committee eventually evolved into the International Society for Nomenclature of Paediatric and Congenital Heart Disease. The working component of this international nomenclature society has been The International Working Group for Mapping and Coding of Nomenclatures for Paediatric and Congenital Heart Disease, also known as the Nomenclature Working Group. The Nomenclature Working Group created the International Paediatric and Congenital Cardiac Code, which is available for free download from the internet at [http://www.IPCCC.NET].In previous publications from the Nomenclature Working Group, unity has been produced by cross-mapping separate systems for coding, as for example in the treatment of the functionally univentricular heart, hypoplastic left heart syndrome, or congenitally corrected transposition. In this manuscript, we review the nomenclature, definition, and classification of heterotaxy, also known as the heterotaxy syndrome, placing special emphasis on the philosophical approach taken by both the Bostonian school of segmental notation developed from the teachings of Van Praagh, and the European school of sequential segmental analysis. The Nomenclature Working Group offers the following definition for the term "heterotaxy": "Heterotaxy is synonymous with 'visceral heterotaxy' and 'heterotaxy syndrome'. Heterotaxy is defined as an abnormality where the internal thoraco-abdominal organs demonstrate abnormal arrangement across the left-right axis of the body. By convention, heterotaxy does not include patients with either the expected usual or normal arrangement of the internal organs along the left-right axis, also known as 'situs solitus', nor patients with complete mirror-imaged arrangement of the internal organs along the left-right axis also known as 'situs inversus'." "Situs ambiguus is defined as an abnormality in which there are components of situs solitus and situs inversus in the same person. Situs ambiguus, therefore, can be considered to be present when the thoracic and abdominal organs are positioned in such a way with respect to each other as to be not clearly lateralised and thus have neither the usual, or normal, nor the mirror-imaged arrangements."The heterotaxy syndrome as thus defined is typically associated with complex cardiovascular malformations. Proper description of the heart in patients with this syndrome requires complete description of both the cardiac relations and the junctional connections of the cardiac segments, with documentation of the arrangement of the atrial appendages, the ventricular topology, the nature of the unions of the segments across the atrioventricular and the ventriculoarterial junctions, the infundibular morphologies, and the relationships of the arterial trunks in space. The position of the heart in the chest, and the orientation of the cardiac apex, must also be described separately. Particular attention is required for the venoatrial connections, since these are so often abnormal. The malformations within the heart are then analysed and described separately as for any patient with suspected congenital cardiac disease. The relationship and arrangement of the remaining thoraco-abdominal organs, including the spleen, the lungs, and the intestines, also must be described separately, because, although common patterns of association have been identified, there are frequent exceptions to these common patterns. One of the clinically important implications of heterotaxy syndrome is that splenic abnormalities are common. Investigation of any patient with the cardiac findings associated with heterotaxy, therefore, should include analysis of splenic morphology. The less than perfect association between the state of the spleen and the form of heart disease implies that splenic morphology should be investigated in all forms of heterotaxy, regardless of the type of cardiac disease. The splenic morphology should not be used to stratify the form of disease within the heart, and the form of cardiac disease should not be used to stratify the state of the spleen. Intestinal malrotation is another frequently associated lesion that must be considered. Some advocate that all patients with heterotaxy, especially those with isomerism of the right atrial appendages or asplenia syndrome, should have a barium study to evaluate for intestinal malrotation, given the associated potential morbidity. The cardiac anatomy and associated cardiac malformations, as well as the relationship and arrangement of the remaining thoraco-abdominal organs, must be described separately. It is only by utilizing this stepwise and logical progression of analysis that it becomes possible to describe correctly, and to classify properly, patients with heterotaxy

An Earth-system prediction initiative for the twenty-first century

International audienceSome scientists have proposed the Earth-System Prediction Initiative (EPI) at the 2007 GEO Summit in Cape Town, South Africa. EPI will draw upon coordination between international programs for Earth system observations, prediction, and warning, such as the WCRP, WWRP, GCOS, and hence contribute to GEO and the GEOSS. It will link with international organizations, such as the International Council for Science (ICSU), Intergovernmental Oceanographic Commission (IOC), UNEP, WMO, and World Health Organization (WHO). The proposed initiative will provide high-resolution climate models that capture the properties of regional high-impact weather events, such as tropical cyclones, heat wave, and sand and dust storms associated within multi-decadal climate projections of climate variability and change. Unprecedented international collaboration and goodwill are necessary for the success of EPI

The combined influence of distance and neighbourhood deprivation on Emergency Department attendance in a large English population: a retrospective database study

YesThe frequency of visits to Emergency Departments (ED) varies greatly between populations. This may reflect variation in patient behaviour, need, accessibility, and service configuration as well as the complex interactions between these factors. This study investigates the relationship between distance, socio-economic deprivation, and proximity to an alternative care setting (a Minor Injuries Unit (MIU)), with particular attention to the interaction between distance and deprivation. It is set in a population of approximately 5.4 million living in central England, which is highly heterogeneous in terms of ethnicity, socio-economics, and distance to hospital. The study data set captured 1,413,363 ED visits made by residents of the region to National Health Service (NHS) hospitals during the financial year 2007/8. Our units of analysis were small units of census geography having an average population of 1,545. Separate regression models were made for children and adults. For each additional kilometre of distance from a hospital, predicted child attendances fell by 2.2% (1.7%-2.6% p<0.001) and predicted adult attendances fell by 1.5% (1.2% -1.8%, p<0.001). Compared to the least deprived quintile, attendances in the most deprived quintile more than doubled for children (incident rate ratio (IRR) = 2.19, (1.90-2.54, p<0.001)) and adults (IRR 2.26, (2.01-2.55, p<0.001)). Proximity of an MIU was significant and both adult and child attendances were greater in populations who lived further away from them, suggesting that MIUs may reduce ED demand. The interaction between distance and deprivation was significant. Attendance in deprived neighbourhoods reduces with distance to a greater degree than in less deprived ones for both adults and children. In conclusion, ED use is related to both deprivation and distance, but the effect of distance is modified by deprivation

Modeling geoelectric fields in Ireland and the UK for space weather applications

Geoelectric fields at the Earth’s surface caused by geomagnetic storms have the potential to disrupt and damage ground-based infrastructure such as electrical power distribution networks, pipelines, and railways. Here we model geoelectric fields in Ireland and the UK during both quiet and active time intervals of geomagnetic conditions using measurements from magnetic observatories and electromagnetic tensor relationships. The analysis focused on (1) defining periods of the magnetic field variations that are largely affected by the geomagnetic storms, between 30 and 30,000 s; (2) constraining the electromagnetic tensor relationships that defines the Earth’s response to magnetic field variations; (3) implementing and validating two approaches for modeling geoelectric fields based on measurements from magnetic observatories and local and interstation electromagnetic transfer functions; and (4) estimating uncertainties when modeling geoelectric fields. The use of interstation tensor relationships allowed us to differentiate between regional and local geomagnetic sources. We found coherence values of 0.5–0.95, signal-to-noise ratio of 1–15 dB, normalized root-mean-square values of 0.8–3.4, and root-mean-square values of 0.7–84 mV/km. Within these ranges of values, sites in close proximity (<100 km) to a magnetic observatory and not affected by local storms will provide the most accurate results, while sites located at further distances and affected by spatially localized features of the storm will be less accurate. These methods enable us to more accurately model geomagnetically induced currents, and their associated uncertainties, in the British and Irish power networks

The Social and Ethical Acceptability of NBICs for Purposes of Human Enhancement: Why Does the Debate Remain Mired in Impasse?

The emergence and development of convergent technologies for the purpose of improving human performance, including nanotechnology, biotechnology, information sciences, and cognitive science (NBICs), open up new horizons in the debates and moral arguments that must be engaged by philosophers who hope to take seriously the question of the ethical and social acceptability of these technologies. This article advances an analysis of the factors that contribute to confusion and discord on the topic, in order to help in understanding why arguments that form a part of the debate between transhumanism and humanism result in a philosophical and ethical impasse: 1. The lack of clarity that emerges from the fact that any given argument deployed (arguments based on nature and human nature, dignity, the good life) can serve as the basis for both the positive and the negative evaluation of NBICs. 2. The impossibility of providing these arguments with foundations that will enable others to deem them acceptable. 3. The difficulty of applying these same arguments to a specific situation. 4. The ineffectiveness of moral argument in a democratic society. The present effort at communication about the difficulties of the argumentation process is intended as a necessary first step towards developing an interdisciplinary response to those difficulties