Le point de vue de Jean-Marie Tjibaou président et organisateur du festival

Tjibaou Jean-Marie, Degorce-Dumas Michel. Le point de vue de Jean-Marie Tjibaou président et organisateur du festival. In: Journal de la Société des océanistes, 100-101, 1995-1-2. pp. 109-115

Caractérisation et suivi du traitement biologique de sols contaminés par des HAP (Hydrocarbures Aromatiques Polycycliques)

National audienc

Utilisation de la photooxydation UV/H2O2 pour l'élimination du carbone organique dissous (COD) dans les effluents contenant des composés non biodégradables

The purpose of this study was to investigate the use of photooxidation UV/H2O2 to remove DOC of industrial effluents and landfill leachates containing biorefractory compounds. Experiments were first conducted on a 7.5mL spiral reactor to examine the effects of pH and H2O2 dosage on DOC removal. It was observed that acidification improved the efficiency of wastewater treatment either by removing humic substances (leachate samples) or by eliminating CO32- and HCO3- ions (both leachate and industrial samples). DOC removal also increased with higher hydrogen peroxide dosage. Nevertheless, there is a dosage in H2O2 over which no improvement is obtained. DOC removal exceeded 90 % on some samples. Using best conditions obtained on spiral recator, effluents have been treated using an annular photoreactor (380 ml). Organic pollution elimination was very satisfying, which is encouraging to continue on more important pilots with several UV lamps and varying irradiation thickness.Ce travail a eu pour but d'étudier l'efficacité de la photooxydation UV/H2O2 sur la réduction du COD d'effluents industriels et de lixiviats de décharge d'ordures ménagères contenant des composés non biodégradables. Les expériences ont d'abord été réalisées sur un réacteur ≪ spirale ≫ de 7,5 mL. L'influence du pH initial a été étudiée. Il apparaît que l'acidification à pH 2 permet d'améliorer l'efficacité du traitement, soit en précipitant des composés de type substances humiques (cas des lixiviats de décharge) soit en éliminant les ions carbonate et hydrogénocarbonate. L'augmentation de la concentration en peroxyde d'hydrogène accroît l'abattement du COD ; néanmoins, il existe une limite au-delà de laquelle il n'y a plus d'amélioration. La réduction de la charge organique dépasse 90 % sur certains effluents. Après avoir défini les conditions du traitement (pH, [H2O2]) en réacteur ≪ spirale ≫, les effluents ont été traités en photoréacteur annulaire (380 mL). L'abattement du COD reste très satisfaisant, ce qui permet d'envisager la poursuite du développement de réacteurs de photooxydation multilampes avec des épaisseurs d'irradiation variables

A biodegradation study of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/organoclay nanocomposites in various environmental conditions

International audiencePoly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/organo-modified montmorillonite (OMMT) nanocomposite films were prepared by melt compounding and cast-film extrusion at various loading rates, i.e. 1, 3 and 5 wt. %. The effect of OMMT on the biodegradability of produced PHBV nanocomposite films was investigated under controlled conditions in aqueous medium (20 degrees C for 28 days) by monitoring the biochemical oxygen demand (BOD), and under laboratory-scale composting conditions (58 degrees C for 70 days) by monitoring the weight and surface loss. The microstructural and macromolecular changes were monitored during the biodegradation process by means of scanning transmission electron microscopy (STEM), differential scanning calorimetry (DSC) and size exclusion chromatography (SEC) analysis. The initial microstructure of the nanocomposites samples exhibited an intercalated structure with a good clay/matrix affinity. BOD evolution in aqueous conditions as well as surface and weight loss in composting conditions indicated that the biodegradation rate of PHBV nanocomposites was lower than neat PHBV, which supports a barrier effect of OMMT. This was confirmed by the surface erosion observed through SEM accompanied by a significant decrease of the average molecular weight in the bulk of the films. Our results demonstrated that the biodegradation of PHBV and nanocomposite films occurred by combined hydrolytic and enzymatic processes, at the surface as well as in the bulk of the material. DSC analysis also revealed no change in the degree of crystallinity, which suggests that the amorphous and crystalline phases were degraded at same rate

Flocculation of Escherichia coli Using a Quaternary Ammonium Salt Grafted Carboxymethyl Chitosan Flocculant

Only few studies are available on bacteria removal efficiencies and antibacterial properties of flocculants, which is one of the important requirements in water treatment work. Escherichia coli (E. coli) was selected as an example of a Gram-negative bacteria for testing the flocculating properties of a quaternary ammonium salt grafted chitosan (carboxy­methyl chitosan-<i>graft</i>-poly­[(2-methacryloyloxyethyl) trimethyl­ammonium chloride] copolymer; i.e., CMC-<i>g</i>-PDMC). The effect of various flocculation parameters, including flocculant dosage, initial bacterial density, nutrient medium content, and pH were successively investigated. The experimental results indicated that, besides flocculation effects, CMC-<i>g</i>-PDMC also exhibited a bactericidal effect (not requiring additional treatment facilities). Moreover, the flocculation mechanisms were investigated via zeta potential measurements, floc observation, and three-dimensional excitation–emission matrix spectra analysis. Apart from its flocculating and settling effect, this chitosan-based material has bactericidal action through the breaking of bacterial cell walls by grafted quaternary ammonium salt