Réduction et contrôle du foisonnement filamenteux des boues activées par application d'un régime turbulent

Le foisonnement filamenteux des boues activées est un problème important dans les stations d'épuration du type Boues Activées, car il peut entraîner des pertes de biomasse avec l'eau épurée. Les techniques de lutte utilisées actuellement sont, soit des techniques dites « biologiques » (sélecteurs), soit des techniques chimiques (floculants, biocides). L'objectif de notre travail a été la mise au point d'un procédé original basé sur la création d'une zone de turbulence pour casser les réseaux filamenteux. La réduction et le contrôle du bulking sont obtenus par passage (de durée limitée T1) de la biomasse dans un système venturi, équipée d'une prise d'air. L'efficacité du procédé dépend principalement de la turbulence due à l'auto-aspiration d'air au niveau du rétrécissement du venturi. Cette turbulence contribue d'une part au mécanisme de « cisaillement » des filaments, et d'autre part à la qualité de l'effluent sortant. Une gestion adaptée (aération séquentielle en procédé à faible charge) permet d'obtenir, outre une amélioration de la décantation, une amélioration de l'élimination de l'azote. De plus, le contrôle de la biomasse optimise l'élimination de la pollution carbonée.The loss of biomass in a waste water plant as a result of sludge bulking is an important problem. Biological (ex.: selector configuration) or chemical (ex. : floculating reagents, biocides...) methods habe been used in order to control bulking. A new process based on the generation of turbulence to break the filaments is described. To reduce and control sludge bulking, the biomass is pumped through a venturi equipped with an air inlet. Figure 1 represents the pilot scheme. Two processes can be used : the emulsor with air is introduced on recycling of sludge or is placed in an independent loop. Here, it is the latter that has been used.We tried to reduce bulking by mechanical treatment. The hydrodynamic efficiency of the process depends mostly on the degree of turbulence generated by the waters speed and by the suction of air in the constricted part of the venturi.During the first trials on the plant, we defined the maximum turbulence allowed in order not to break the floc. We could not use a big aeration to prevent defloculation.The main factors to reduce bulking are :- the sequences of usage of the emulsor venturi (the periodicity of the treatment is T),- the speed of the water in the nozzle of the venturi (we can refer to the Reynolds Number Re = Ud/ʋ; but this number can’t really represent the turbulence created),- the duration of the emulsor's application. The emulsor venturi is used during a period T1 with a periodicity T (T>T1), with T1 : n X (VR/qv) where VR/qv is the contact time in the venturi and n is the frequence of recycling.During the period T, it is possible to use continuous aeration or to work with sequential aeration.a) continuous aeration|_________________________| TTime between two applications of the venturi|_______________| T1Venturi durationThe process is the same as the aeration of activated sludge. COD is reduced but only with low load, significant nitrification occurs. Figure 5 shows the efficiency of the continuous aeration process especially versus the sludge index parameter.b) sequential aerationAs we try to remove nitrogen, the sequential aeration is more useful than continuous aeration. A cycle is divided in two periods (T2, T3 with T = T2 + T3), and of course, the duration of the venturi use equal to T1.|_________________________| TTime between two applications of the venturi|_____________| T1Venturi duration|_________________| T2Aeration duration          |_____| T3Anoxic periodFigures 6 and 7 show the efficiency of the emulsor if we consider lB (sludge index) as the main parameter for the sequential operation (T2, T3) and it's also possible to obtain a good removal of nitrogen pollution.Our operations parameters were for these experiments :T = 8 or 12 hoursT1 between 20 min. and 1 hourT2 between 4 and 5 hoursThis process is now patiented and the first industrial applications are now defined

Establishment and characterization of three cell lines from Aedes triseriatus (Diptera : Culicidae)

International audienc

PDB8 TYPE-2 DIABETES AND BODY MASS INDEX (BMI):WHAT CAN WE LEARN FROM A LONGITUDINAL DATABASE STUDY?

Farrando, Jordi;Febles, Maria Dolors ;Henrich, Jordi;Tarrasó, Olga ;Fuertes, J.C.;Pérez, S

Thermal Diffusion of a Two Layer System

In this paper thermal conductivity and thermal diffusivity of a two layer system is examined from the theoretical point of view. We use the one dimensional heat diffusion equation with the appropriate solution in each layer and boundary conditions at the interfaces to calculate the heat transport in this bounded system. We also consider the heat flux at the surface of the samle as boundary condition instead of using a fixed tempertaure. From this, we obtain an expression for the efective thermal diffusivity of the composite sample in terms of the thermal diffusivity of its constituent materials whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag

Decay resistance against Coriolus versicolor in Sessile oak ( Quercus petraea Liebl.): analysis of the between-tree variability and correlations with extractives, tree growth and other basic wood properties

Abstract : Weight loss due to fungus Coriolus versicolor has been measured on 614 samples according to the NF EN 113 norm. Up to eight samples were cut at breast height (two opposite radii×four radial positions in heartwood) from 82 mature sessile oaks ( Quercus petraea Liebl.) originating from contrasting regions, silvicultural schedules and site qualities in France. The following points are addressed in the paper: (i) contribution to the total variability for weight loss of the effects "tree”, "position in the tree”, as well as their interaction; (ii) percentage of wood samples and trees in each of the five classes of natural durability defined by the norm NF EN 350-2; (iii) test of the effects of region, silvicultural schedule and site quality on weight loss and evaluating their contribution to the total variation; and (iv) correlations at tree level between weight loss and several traits related to tree growth and basic wood properties (density, swelling, grain angle, multiseriate wood rays characteristics, extractives content). The results are discussed with a view to aid the forest manager as well as the log/wood user to take advantage of the high level of between-tree variability observed as natural durability against C. versicolo

Asymptotics of Random Contractions

In this paper we discuss the asymptotic behaviour of random contractions $X=RS$, where $R$, with distribution function $F$, is a positive random variable independent of $S\in (0,1)$. Random contractions appear naturally in insurance and finance. Our principal contribution is the derivation of the tail asymptotics of $X$ assuming that $F$ is in the max-domain of attraction of an extreme value distribution and the distribution function of $S$ satisfies a regular variation property. We apply our result to derive the asymptotics of the probability of ruin for a particular discrete-time risk model. Further we quantify in our asymptotic setting the effect of the random scaling on the Conditional Tail Expectations, risk aggregation, and derive the joint asymptotic distribution of linear combinations of random contractions.Comment: 25 page

Reducing the impact of radioactivity on quantum circuits in a deep-underground facility

As quantum coherence times of superconducting circuits have increased from nanoseconds to hundreds of microseconds, they are currently one of the leading platforms for quantum information processing. However, coherence needs to further improve by orders of magnitude to reduce the prohibitive hardware overhead of current error correction schemes. Reaching this goal hinges on reducing the density of broken Cooper pairs, so-called quasiparticles. Here, we show that environmental radioactivity is a significant source of nonequilibrium quasiparticles. Moreover, ionizing radiation introduces time-correlated quasiparticle bursts in resonators on the same chip, further complicating quantum error correction. Operating in a deep-underground lead-shielded cryostat decreases the quasiparticle burst rate by a factor fifty and reduces dissipation up to a factor four, showcasing the importance of radiation abatement in future solid-state quantum hardware

Distorted Copulas: Constructions and Tail Dependence

Given a copula C, we examine under which conditions on an order isomorphism ψ of [0, 1] the distortion C ψ: [0, 1]2 → [0, 1], C ψ(x, y) = ψ{C[ψ−1(x), ψ−1(y)]} is again a copula. In particular, when the copula C is totally positive of order 2, we give a sufficient condition on ψ that ensures that any distortion of C by means of ψ is again a copula. The presented results allow us to introduce in a more flexible way families of copulas exhibiting different behavior in the tails

Oakscan: procédé de mesure rapide et non destructif des polyphénols du bois de chêne de tonnellerie

Les polyphénols extractibles contenus dans le bois de chêne des barriques de tonnellerie sont des composés très importants car ils ont une influence sur la couleur et sur les propriétés organoleptiques des vins qu'ils enrichissent. Les analyses chimiques de laboratoire qui permettent de les mesurer sont réalisées sur des extractions, nécessitent un délai de réalisation très long et ne permettent d'analyser que des lots de matière par échantillonnage. Le procédé de mesure rapide et non destructif Oakscan® a été développé par la tonnellerie Radoux. Il se fonde sur la spectrométrie proche infrarouge et permet de mesurer la teneur en polyphénols en quelques secondes, directement sur le bois massif. Le contenu polyphénolique de chaque douelle est alors mesuré, permettant une meilleure maitrise de la matière première entrant dans la composition des fûts