| Environnement, ingénierie & développement |  |
N°29 - 1er Trimestre 2003
1. La recherche d’un procédé viable de valorisation d’un phosphogypse provenant de l’industrie phosphatière marocaine
About seven million tons of phosphogypsum per year are dumped into sea generated from a phosphoric acid plant in Jorf Lasfar, Morocco. The objective ofthe present study is to find a solution in order toreuse this material by considering both techno-economicand environmental constraints. These materialsare usually used as a filling material in roadconstructions. A literature survey is presented on theuse phosphogypsum for production of constructionmaterials (plasters, cements), in the domain of geotechniquesand agriculture. This paper also presentsthe laboratory scale work according to Puiatti. It was observed that the mechanical strength of phopogypsum was improved by addition of 20 weight% mud of ankarite base, which is a natural material and have a negligible cost. This mixture has a mechanical resistance passed 0.25 to 0.85 MPa, the same mechanical strength was obtained by addition of 7weight% cement reported by Puiatti. The mechanicalresistance of this mixture permits it to be agood construction material.
2. La stratégie de la Roumanie sur la gestion des déchets
This paper presents the main strategy tasks for Romania on the wastes management taking into account the analysis made in 2000. This analysis reflects a strong increase of the urban wastes low heat value in the last 10 years, which leads to extended wastes treatment ways, such as: energy recovery incineration and methanisation. There are presented the general appropriate targets,and the tasks in the urban, industrials and toxics wastesmanagement. Romania strategy regarding the wastes management involves the next steps: the analysis of the situation in 2000, problems identification, the strategic goals settlement, the elaboration of wastes management national work frame. The application of the wastes management nationalstrategy starting with 2002 will provide the conditionsfor the application of European Union legislation on thewastes in Romania starting with 2007, the date ofRomania acceptation in the EU.
3. Aide au dimensionnement et à l'optimisation d'une installation de tri-compostage : modélisation des trommels
Trommels are used in the field of the waste management, in particular for biological treatment processes. The trommel is the basic facility implemented to sort out impurities through size classification. It is implemented in the process for compost sorting after the biological degradation as well as for the primary sorting of waste. Research in the field of process analysis of waste treatment is at its beginnings. The development of a phenomenological model for trommels dedicated to municipal solid waste will allow a more accurate knowledge of the performance of such facilities. Results of the modelling allow to take into account both the characteristics of the trommel and the characteristics of the waste input to predict the quantity and the quality of the output products. Included to the simulation platform of the Usim Pac software, the model is able to predict the performance of a trommel, to optimise its operation, as well as to study the effects of the addition or the substitution of one trommel in a given treatment process. This model is an aid tool for process analysis for designers, experts and managers of municipal solid waste treatment.
4. Combinaisons de traitements physico-chimiques et biologiques pour une production de boues réduite: Revue bibliographique
This paper is a review of different physico-chemical treatments that can be combined to biological treatments with the aim of sludge production reduction. Mechanical, thermo-chemical and ozone treatmentsfor sludge disintegration are presented, they are combinedwith aerobic and anaerobic digestions in classicalreactors or in membrane bioreactors. The stressis put on i) the potentialities of theses treatmentsand cotreatments to reduce the sludge productioneither during the wastewater treatments or during thesludge treatments, ii) on the effects of the treatmentson the whole treatment process performances and onthe physical properties of the sludges.
5. Impact sur les sols des dioxines de MIOM utilisés en technique routière
Municipal Solid Waste Incineration Bottom Ash (MSWIBA) has been used, in France, in road construction for more than ten years. This practice regulated by the French authority induces episodically various discussion concerning particularly the content of PolyChlorinated Dibenzo-p-Dioxins and PolyChlorinated DibenzoFurans PCDD/F (commonly named dioxins) in this materials and their release through the environment. In order to study the potential transfer of dioxins towards the underlying soil, the collection of the MSWIBA samples used in different roadways manufactured in different periods has been performed. At the same time, percolated water and underlying soils have been investigated. Investigations have shown that the relationship is established between the age of the road conception and the dioxins content in the MSWIBA used. The grain size distribution by laser diffraction, the fixation of the dioxins by the geotextile underlying the MSWIBA layer and the filtration of the percolation water of the MSWIBA showed that dioxins transfer is performed through the particles forms having a minimum size of 0,45µm. In addition, the nature of the underlying soil seems to take an important part in the transfer or immobilization of dioxins.
6. Les cendres d'incinération de boues de stations de traitement des eaux polluées sont-elles utilisables dans les matrices cimentaires ?: Comparaison avec les cendres volantes de charbon
Specific incineration is often used method to eliminate sewage sludge. However, this treatment process produces ashes that must be managed and one way to recover these ashes is utilised them as supplementary cementitious materials. The aim of this study is to characterize a sample of a French sewage sludge ash (SSA), in order to evaluate its binding potential in comparison with other mineral admixtures, as coal fly ashes, already used in concrete. The results show that this sewage sludge ash, even if its characteristics are strongly different from those of classical coal fly ashes, can be used in cementitious materials, since the mechanical properties obtained on mortars are satisfactory. However, the specific characteristics of SSA, i.e. a significant content of phosphorus and an irregular shape due to a strong particle clustering, must be taken into account, since they lead to an increase of the water demand and the setting time of cement. These effects are different than those obtained when classical coal fly ashes are used, showing that it is necessary to avoid abusive comparison between the two ashes. Even if the results are encouraging, additional environmental assessment must be performed before any industrial application.