International audience | Polycyclic Aromatic Hydrocarbons (PAHs) are known for their adverse and cumulative effects at low concentration. In particular, the PAHs accumulate in sewage sludge during wastewater treatment, and may thereafter contaminate agricultural soils by spreading sludge on land. Therefore, sludge treatment processes constitute the unique opportunity of PAH removal before their release in the environment. In this study, the ability of aerobic microorganisms to degrade light and heavy PAHs was investigated in continuous bioreactors treating trace-level PAH-contaminated sludge.

Les changements de productivité des forêts ont été étudiés intensément à partir des années 1990, à la suite des événements relatifs au dépérissement des forêts européennes. Dans cette contribution, on analyse les problèmes méthodologiques soulevés par ce type d'étude, les sources de données disponibles pour l'analyse, et les éléments de diagnostic acquis sur plusieurs espèces forestières du territoire français. Les implications pour le cadre théorique qui prévalait dans les années 1980 concernant la productivité des peuplements forestiers sont enfin discutées. problèmes méthodologiques, sources de données, cadre théorique, éléments du diagnostic

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Larval stages of bivalve molluscs are highly sensitive to pollutants. Oysters from a hatchery from Normandy (English Channel) were induced to spawn, and fertilized eggs were exposed to copper or cadmium for 24 h. Metal accumulation (from 0.125 to 5 mu g Cu L-1 and from 25 to 200 mu g Cd L-1) and MT concentrations were measured in larvae. Compared to controls, larvae accumulated copper and cadmium with an increase in MT concentrations particularly with cadmium (i.e. 130.96 ng Cu (mg protein)(-1) and 12.69 mu g MT (mg protein)(-1) at 1 mu g Cu L-1 versus 23.19 ng Cu (mg protein)(-1) and 8.92 mu g MT (mg protein)(-1) in control larvae; 334.3 ng Cd (mg protein)(-1) and 11.70 mu g MT (mg protein)(-1) at 200 mu g Cd L-1 versus 0.87 ng Cd (mg protein)(-1) and 4.60 mu g MT (mg protein)(-1) in control larvae). Larvae were also obtained from oysters of a clean area (Arcachon Bay) and a polluted zone (Bidassoa estuary) and exposed to copper in the laboratory, their MT concentration was measured as well as biomarkers of oxidative stress. Biomarker responses and sensitivity to copper for the larvae from Arcachon oysters were higher than for those from Bidassoa.

The mussel, Brachidontes variabilis, and the limpet, Patella sp., were used as indicators to monitor cadmium, lead and mercury concentrations along the Lebanese coast. Studies were carried out in order to define the best strategy for assessing and minimizing the effects of size and physiological condition on the metal contents of the molluscs, and corrective models were constructed. Metal concentrations in surface water were measured to estimate bioconcentration factors (BCFs). The BCFs varied from 8.3 x 10(3) to 3.4 x 10(4), from 7.5 x 10(3) to 8.0 X 10(3) and from 3.0 x 10(4) to 3.2 x 10(4), for Cd, Pb and Hg, respectively. For limpets, BCFs varied from 1.7 x 10(4) to 7.4 x 10(4) for Cd, from 2.5 x 10(3) to 6 x 103 for Pb and remained fairly constant at around 104 for Hg. The highest BCFs were associated with lowest contamination levels. The results of the geographical survey exhibited a similar large-scale spatial pattern for the two species and followed the metal concentration distributions measured in the waters.

This study aimed at comparing toxic element (Hg, Cd) bioaccumulation in relation to age for bottlenose (Tursiops truncatus) and striped dolphins (Stenella coeruleoalba) from Mediterranean and Atlantic waters. Metal concentrations were also measured in selected prey to infer metal exposure through the diet. As expected, Mediterranean prey exhibited the highest Hg levels, probably as a consequence of the Hg enrichment of the Mediterranean Sea. Comparing the predators from each area and taking age into account, Mediterranean bottlenose dolphins displayed higher Hg levels than Atlantic dolphins (p = 0.032), whereas Mediterranean striped dolphins did not (p = 0.691). The consumption of Myctophid fish, which showed the highest Hg levels (105 +/- 80 ng g(-1) w.wt.) among Atlantic prey, may explain the high Hg levels in the liver of the Atlantic striped dolphins and suggested a preferential offshore feeding behaviour in this area. Concerning Cd, no clear differences were found between geographical areas. (c) 2006 Elsevier Ltd. All rights reserved.

[Departement_IRSTEA]MA [TR1_IRSTEA]TED / EPURE | The constraints on sanitation in Mayotte, a small French island with a tropical climate in the straight of Mozambique are strong: The interior landscape is rugged with seep slopes, a dense and very rapidly increasing population lives mostly along the coastline, where space for human activity becomes scarce. Yet, the generalization of access to tap water on a household or community level immediately created a need for sanitation programs. Because of the size of the plots and the nature of the subsoil however, onsite sanitation is often impossible and centralized sewerage systems not affordable in the near future. The most appropriate solutions seem to be decentralized low maintenance treatment systems of a capacity of a few hundred person-equivalent, which can be build using mostly local resources, do not require high technical expertise and have low running costs. In order to meet these challenges, SIEAM, the local syndicate which will operate all sewage treatment equipment on the island, asked for expert back-up from Cemagref and asked SINT to design two pilot plants using constructed wetlands. The first constructed wetland plant consists of an Imhoff tank followed by a sub-surface horizontal flow filter with local filter material; divided in three compartments, each planted with different local plants. The second plant is a local adaptation of the type of vertical flow systems working with raw sewage, like the one SINT designs and constructs in Europe. Because sand for a second stage vertical filter is not found on the island, a design with a single stage filter with recirculation was chosen. Both pilot plants are working very well, but in order to optimize dimensioning and to reduce the required surface area, they will have to be tested under higher loadings. | Les contraintes de l'assainissement à Mayotte, une petite île dont le climat est tropical dans le canal du Mozambique, sont fortes: la topographie est très pentue, une population dense et croissant rapidement vit le long de la côte où les espaces pour les activités humaines sont réduits.

To improve total nitrogen removal, a full-scale experimental study was conducted on a hybrid constructed wetlands plant designed for 100 p.e.. The plant composed of a 1st stage of vertical filters (fed with raw wastewater) followed by a 2nd stage of horizontal filters was monitored over one year measuring hydraulic conditions, physico-chemical conditions, gas emission, oxygen of the gas phase and regular treatment performances by 24 h composite samples. Different vertical filter configurations (media depth, intermediate and passive aeration system) were tested as well as two horizontal filter designs. The N removal is discussed on efficiency of each stage in relation to the season and the load applied. This study leads to draw the limit of the plant configuration and gives some design avenues of hybrid systems to reach high and regular level of nitrogen removal with acceptable surface area per person.

Within the scope of studying the hydraulic behaviour of vertical-flow wetland in order to model these systems, differential pressure transducers were used on experimental vertical sand columns to understand the effects of a batch feed on the gaseous and hydraulic phases. Three transducers were set up at three different depths in the column. The system operates in a batch mode. Two types of flow regime were tested. The first one consists of one batch of 10 litres every 8 hours. In this regime, the transducer signal shows four consecutive phases: the influence of the water head on the top of the filter and the infiltration of the batch inside the filter that both increase the pressure, the drainage of the pores that decrease the pressure to a depression and finally the aeration of the pores that restore the pressure to atmospheric pressure. For the second flow regime (a batch of 4 litres every 3 hours) the same consecutive steps are present except the infiltration of the batch. In addition, the drainage and the aeration of the pores are simultaneous over the entire depth of the column and are incidental to the end of the surface dewatering. This is not the case for the first regime where occurrence of those steps depends on the depth. In addition to the understanding of the different steps occurring when a batch volume percolates, those measurements provide useful information on the saturation of the media, the rate of drainage and aeration of the pore, the gas flow, the infiltration rate.