Automatisation et comparaison de différentes méthodes respirométriques d'estimation rapide de la DBO

II est bien connu que la DBO peut étre mesurée par des méthodes respiromédriques. Les manipulations sont ainsi rendues plus aisées mais la durée de la mesure reste inchangée. La demande biologique en oxygène à court terme (DBOACT) a été proposée pour évaluer rapidement la DBO. Habituellement, ces mesures étaient réalisées dans un respiromètre fermé avec une boue acclimatée et en état de respiration endogène. Récemment on a suggéré de travailler avec un respiromètre ouvert, aéré continuellement durant le test. Nous avons réalisé un tel appareil avec une acquisition et un traitement automatique des données, en utilisant un micro-ordinateur. De cette façon, il est facile de tester différentes méthodes (intégration de la courbe en sac, hauteur de pic, comparaison à des étalons, usage d'étalons internes) pour évaluer la DBO. Nous avons également examiné l'influence du type de substrat, de l'âge et des caractéristiques des boues. Notre conclusion est que aucune des méthodes testées ne fournit une détermination précise de la DBO5 pour des substrats complexes. La méthode reste utile pour contrôler la variabilité de l'influent dans une station d'épuration, lorsque la biomasse est acclimatée au substrat et qu'on ne désire pas une mesure très précise.The usual way of measuring BOD is the dilution method. The consumption of oxygen is measured in the dark at 20 °C during 5 days. Manometric methods were proposed already some decades ago. Their principle is that every molecule of oxygen consumed la transformed into CO2 which is absorbed in a solution of KOH, creating a pressure variation in the bottle. From this pressure variation the BOD can be calculated. By this way experiments were made easier but the duration of the measure remained unchanged. Other respirometric methods were also proposed, especially Short Term Biological Oxygen Demand (STBOD) to evaluate BOD rapidly. Usually such determinations were done in closed respirometers with acclimated sludge under endogeneous respiration condition. Recently, it was suggested to proceed in an open respirometer aerated continuously during the test. We set up this type of respirometer with acquisition and automatic processing of the data, using a microcomputer. In this way it was easy to test different procedures. Among these procedures we tested :- the method of integration of curve in sack-from,- the method of peak level,- the method of comparison to standards,- the method of internal standards.The principles of these methods are given in more detail in the text. We examined the influence of the type of substrate, of the type of biomass used and of the sludge retention time on the results. The substrates tested were :- glucose,- domestic waste water with and without detergent,- diluted eggs,- diluted beer,- effluents from the paper industry.Three different types of biomass and these sludge retention times (fresh, 5 days and 20 days) were used. Automatisation of the test and automatic processing of the data were carried out in basic language with an « Apple II » microcomputer.The test lasted between 37' and 3 hours 10', depending on the conditions (substrate, concentration, type of sludge,...)Analysis of the results were computerized by the Analysis of Variance (ANO-VA) method and results are lasted in 3 tables.From this study we can conclude that STOD methods have some advantages :- they are much faster than the classical method,- they can be easily automatized,- they are cheap,- oxygen is really consumed by biological processes.For simple substrates these methods can lead to good results but for complex substrates reproductibility and precision are rather poor. Among the methods tested the only acceptable one seems to be the integration of the curve in sack-form. Lack of reproductibility appears to be intrinsic to the method.Some possible improvements are presented, such as washing the activated sludge between two experiments, but are not very practical.Despite these limitations the method can be useful to control the variability of influent in a sewage treatment plant. In such a case, the biomass is acclimated to the substrate and variations of influent BOD can be measured

Windsurfing : an extreme form of material and embodied interaction?

This paper makes reference to the development of water based board sports in the world of adventure or action games. With a specific focus on windsurfing, we use Parlebas (1999) and Warnier's (2001) theoretical interests in the praxaeology of physical learning as well as Mauss' (1935) work on techniques of the body. We also consider the implications of Csikzentimihalyi's notion of flow (1975). We argue that windsurfing equipment should not merely be seen as protection but rather as status objects through which extreme lifestyles are embodied and embodying

An Adaptive Resonance Theory account of the implicit learning of orthographic word forms

WOS:000276123600003International audienceAn Adaptive Resonance Theory (ART) network was trained to identify unique orthographic word forms. Each word input to the model was represented as an unordered set of ordered letter pairs (open bigrams) that implement a flexible prelexical orthographic code. The network learned to map this prelexical orthographic code onto unique word representations (orthographic word forms). The network was trained on a realistic corpus of reading textbooks used in French primary schools. The amount of training was strictly identical to children's exposure to reading material from grade 1 to grade 5. Network performance was examined at each grade level. Adjustment of the learning and vigilance parameters of the network allowed us to reproduce the developmental growth of word identification performance seen in children. The network exhibited a word frequency effect and was found to be sensitive to the order of presentation of word inputs, particularly with low frequency words. These words were better learned with a randomized presentation order compared with the order of presentation in the school books. These results open up interesting perspectives for the application of ART networks in the study of the dynamics of learning to read. (C) 2009 Elsevier Ltd. All rights reserved