| Environnement, ingénierie & développement |  |
N°60 - Juin 2011
1. Maîtrise des impacts environnementaux par la modélisation du système physique
The certification ISO 14001 knows a significant distribution (broadcasting). Indeed, under the combined effects of the degradation of the natural circles and the competition, the current company has to adopt an environmental strategy at the level of all its activities, by the implementation of an Environmental Management system (EMS).The environment is in the hear t of the systems of production so obliging companies to wonder and to report their environmental performances. So, an analysis of all the activities of the company highlights Significant Environmental Impacts (SEI).To make a first stage towards the integration of the environment, these SEI must be mastered by corrective actions at the level of the installations. To do it, it is necessary to model the operational system where from the use of the method GRAICO, which squeezed (tightened) to complete by the method Analyzes Failures and their Consequences (ADC) for controlled these impacts.
2. Stratégies graduées d’évaluation des risques environnementaux induits par les sédiments fluviaux : revue bibliographique sur la caractérisation des risques et des incertitudes associées
Sediments are an essential component of fluvial ecosystems; in the meantime, they can also disturb these systems and their uses. Management of these perturbations, for instance dredging, may also yield adverse effects on the environment; these adverse effects may be increased as sediments are prone to accumulate metals or hydrophobic organic substances. Several industrialized countries have adopted assessment frameworks for sediments; these frameworks have progressively shifted from hazard to ecological risk assessment. Most frameworks are tiered, and involve increasingly sophisticated approaches at higher tiers. In the context of DIESE, a research project granted by the French national research agency (ANR) and aiming to develop a sediment assessment framework for sediments stored upstream dams; we performed a literature survey, with a focus on risk characterization and uncertainty assessment. The sediment assessment frameworks can be grouped in two categories: (i) some derive from the “triad” concept, where the results of the assessment determine the applicable management option; (ii) in the second group, analyses are tuned as a function of the selected management option. Rather few papers cope with risk characterization; in the case of sediments, the very nature of variables contributing to risk leads to qualitative or semi-quantitative methods. Considering that there are other important sources of uncertainty than measurement errors, again qualitative or […]
3. Stabilisation des métaux et dégradation biologique des polluants organiques dans un sédiment portuaire contaminé
The management of dredged sediments is problematic in some French regions due to their significant contamination by organic and/or mineral pollutants. In this study, dredged sediment from a seaport was treated by composting and chemical stabilization. Sediment contamination (organic and mineral pollutants) was characterized, and samples (control and stabilized samples) weighing 6 kg were treated with different mineral additives in a small scale pilot. Results show that (i) total flux of pollutants is reduced by half in samples treated with hematite and zero-valent iron, (ii) fine zeolite (clinoptilolite) is unsuitable to stabilize pollutants in the sediment, (iii) composting reduces organotin concentrations between 38 and 91%, and total PAH level at 15%.
4. Valorisation des déchets de démolition comme granulats pour bétons
The demolished materials recycling responds to concerns conserve or to economize natural aggregates for the requirements to functioning of building sites. The project aim is also to protect environment by reducing uncontrolled dump sites of rubble. Nevertheless, the use of this kind of aggregates may cause problems, due to their high porosity which resulting an absorption of mixing water (difficulty to control of concrete fresh proper ties) and consequently a decrease the strength and durability of concrete.This experimental work is conducted in order to recover aggregates resulting from demolished concretes. Tests of physical and mechanical characterization of recycled aggregates (sand and gravel), were performed in order to set up compliance to the standardization. Concretes of different granular combinations (natural/recycled) with and without addition of superplasticizer are composed, as well as application of various ratios (gravel/sand).Also, the proper ties of these kinds of concretes were tested in fresh and hardened forms. The application of the recycled aggregates resulted in an evidence that they can be providing a concrete with resisting characteristic of 28 days quite higher than 20 MPa. The combinations of natural/recycled aggregates can be considered for certain applications without major risk.
5. Evaluation du potentiel de valorisation par digestion anaérobie des gisements de déchets organiques d’origine agricole et assimilés en Haïti
Agricultural and similar residues are characterized by their ability to be converted through aerobic and anaerobic biological treatments and to be rapidly decomposed, particularly in tropical climate countries. These residues contribute to the emission of odors, air pollution, groundwater and surface water pollution and proliferation of insect diseases. Anaerobic digestion is of great interest particularly in the context of the precarious conditions in countries like Haiti, not only because it contributes to fermentable organic waste treatment and prevention of the negative impacts mentioned above, but also because it offers products of high energy (methane) and fertilizer (digestate) value.There has yet to be identified a systematic study quantifying and characterizing bio-physic and chemical fractions of organic wastes from agriculture in Haiti. This paper provides an initial contribution to the quantitative assessment of mass and energy potential from organic residues generated by agriculture. This study reveals that combined deposits of plant and animal residues are about 2.0 x 106 tons of organic matter, which corresponds to a potential production of 3.5 x 108 m3 of methane through anaerobic digestion. Further works and field surveys can refine this assessment by considering smaller time intervals and a finer geographic network.