International audience

International audience

International audience

Correspondance: BRGM, av. Claude Guillemin, 45060 Orleans, Cedex 2, France | International audience | The treatment of a cyanidation effluent containing thiocyanate, free cyanide, and complexed cyanide was con tinuously performed for a period of 6 months. Activated carbon, pozzolana, and a mixture of pumice stone and zeolite were tested as supports in fixed bed reactors. Activated carbon adsorbed the different forms of cyanide. In contrast, the other supports did not remove any pollutants from the effluent during an adsorption experiment. All supports successfully allowed fixation of bacteria. More than 90% of the thiocyanate was biologically decomposed into NH4 +, C02 and S042, even when increasing the feed flow-rate and the pollutant concentrations. Free and complexed cyanides were eliminated, probably through a combination of precipitation and biological degradation. The oxidation of ammonium into nitrate was only performed by the activated carbon-containing column and with the more diluted feeding. The nitrification process was inhibited in all reactors when the cyanide concentrations and feed flow-rates were increased

[Departement_IRSTEA]EEE [TR1_IRSTEA]E33-Maîtrise et gestion des déchets | International audience | It is well-known that heavy metals brought by intensive pig slurry applications accumulate in the soil ; because of their potential impact on the environment, studying their behaviour is of utmost interest. The Solepur process has been developed in Brittany (France) where pig farming causes serious environmental problems ; it enables the soil to be used as a treatment medium to process pig slurry. Numerous pig slurry applications were performed from 1991 to 1995 on an experimental hydrologically-isolated field specially equipped to recover all the leachate. These applications approximately corresponded to the amount which might have been spread over one century. The Solepur process can be considered as a simulation model for what happens to metals in pig slurry under normal field conditions over a long period of time. This work measured the concentrations of Cu, Zn, Mn, Co, Fe, Cd in pig slurry, in soil and in drainage water, and the results are discussed. Total concentrations and specification data within the three different compartments were analysed and showed that Cu and Zn accumulate in the surface layer, whereas other metals, such as Mn and Co, dissolve and are washed away in the leachate. The increase in the bioavailability and toxicity of these metals as well as their impact on the environment are discussed. | Il est bien connu que les métaux-lourds apportés par des épandages intensifs de lisier de porc s'accumulent dans le sol ; l'étude de leur comportement est donc de la plus haute importance étant donné leur impact potentiel sur l'environnement. Le procédé Solépur a été développé en Bretagne (France), où l'élevage porcin engendre de sérieux problèmes environnementaux ; ce procédé utilise le sol comme un intermédiaire épuratif dans le traitement du lisier de porc. Des épandages répétés de lisier, correspondant approximativement à un siècle d'épandage, ont été réalisés de 1991 à 1995 sur un champ expérimental isolé et équipé de façon à récolter totalement l'eau de drainage. Cette étude est consacrée à la mesure des concentrations de Cu, Zn, Mn, Co, Fe et Cd dans le lisier de porc, le sol et l'eau de drainage. Les concentrations totales et celles résultant de la spéciation chimique sont analysées dans ces trois compartiments et permettent de montrer que certains métaux (Cu et Zn) s'accumulent dans la couche de surface, alors que d'autres (Co et Mn) sont lessivés. L'accroissement de leur toxicité et de leur biodisponibilité ainsi que leur impact sur l'environnement sont également discutés.