L'article présente l'application de l'Analyse du Cycle de Vie (ACV) à un système d'assainissement complet, incluant le réseau d'égout. Il présente d'abord les hypothèses retenues pour l'ACV concernant les deux systèmes de traitement des eaux usées ayant tous les deux la même charge nominale quotidienne de la DBO 5 et associés au même réseau d'égouts. Ces systèmes correspondent respectivement à (i) un "filtre planté de roseaux à lit vertical (VFCW)" pour lequelle un inventaire détaillé des flux émis et des ressources consommées a été élaboré et (ii) une STEP à « boues activées » boues » issue de la base de données d'ACV Ecoinvent LCI. Les résultats d'ACV soulignent l'importance de l'eutrophisation qui peut facilement s'expliquer par la suppression incomplète de l'azote total et du phosphore total dans un VFCW. De façon plus surprenante, l'impact du réseau semble considérable. Enfin, l'article analyse l'applicabilité et les limites de l'ACV pour les systèmes de traitement des eaux usées. / The article presents the application of Life Cycle Assessment (LCA) to a complete sanitation system including the sewer network. It first describes the LCA hypothesis which concerns two types of waste water-treatment plant with the same daily nominal load in BOD5 and associated to the same sewer network derived from the Life Cycle Inventory (LCI) database Ecoinvent. The two wastewater treatment systems compared are (i) a Vertical Flow Constructed Wetlands (VFCW) for which a detailed inventory was elaborated and (ii) an activated sludge stemming from the LCI database Ecoinvent. LCA scores of VFCW highlight the importance of eutrophication which can be easily explained by the incomplete removal of total N and total P in a VFCW. In a more surprising way, the impact of the network seems considerable. Finally, the article analyses the applicability and limitations of LCA for wastewater treatment with regard to water quality and the needed improvements of water status in LCA.

The MAPPE GIS based multimedia model is used to produce a quantitative description of the behaviour of γ-hexachlorocyclohexane (γ-HCH) in Europe, with emphasis on continental surface waters. The model is found to reasonably reproduce γ-HCH distributions and variations along the years in atmosphere and soil; for continental surface waters, concentrations were reasonably well predicted for year 1995, when lindane was still used in agriculture, while for 2005, assuming severe restrictions in use, yields to substantial underestimation. Much better results were yielded when same mode of release as in 1995 was considered, supporting the conjecture that for γ-HCH, emission data rather that model structure and parameterization can be responsible for wrong estimation of concentrations. Future research should be directed to improve the quality of emission data. Joint interpretation of monitoring and modelling results, highlights that lindane emissions in Europe, despite the marked decreasing trend, persist beyond the provisions of existing legislation. An spatially-explicit multimedia modelling strategy was applied to describe the historical distribution of γ-HCH in European soils and surface waters.

International audience | We assessed the temporal variability of nutrients, phytoplankton and bacterioplankton at two sites of different trophic status in New Caledonia's South-West lagoon, a tropical coastal ecosystem. During stable meteorological conditions, Chl.a, bacterial production and nutrient concentrations experience weak but consistent daily variation. Short-term (1–2 week interval) fluctuations of planktonic variables are in the same range as annual variations at both sites. A part of these short term variations is linked to local meteorological events (wind in the main channel, precipitation at the coastal station). Although annual variations are weak compared to short term variations, phytoplankton and bacterioplankton production show consistent temporal patterns, with maxima in December–January and April–May and minima in August. Annual bacterial production represents 21% and 34% of particulate primary production at the oligotrophic and mesotrophic sites, respectively. Mineral nutrient availability indicates that nitrogen is probably the primary limiting factor of phytoplankton throughout the year.

Poster session | International audience

Poster session | International audience

This study examines the common ground between current scientific knowledge and stakeholders’ perception of ecosystem services in mixed forests versus monocultures. An enquiry was performed within the frame of the project FORBIO aiming at the ‘Assessment of the effects of tree species BIOdiversity on FORest ecosystem functioning’ (http://forbio.biodiversity.be). The objective of this enquiry was to confront the perception of the influence of mixed species stands on ecosystem services in Belgium with actual scientific knowledge. The target groups were forest managers, users and scientists. As a general frame for the questionnaire, the ‘Millenium Ecosystem Assessment’, assessing the consequences of ecosystem change for human well-being, was selected. Respondents were asked to express their degree of agreement with statements related to the provisioning (production/quality, financial return), supporting (biodiversity, nutrient cycling, resistance), regulating (climate, air, soil, water) and cultural (aesthetics, recreation) ecosystem services, comparing mixed species to pure stands. Other questions addressed management objectives and the general profile of participants. The web-based questionnaires (SurveyMonkey) were established in Flemish and in French and invitations to respond were distributed by e-mail among key contact persons of forestry/nature associations, forest managers and scientists. After one month, a total of 142 and 228 responses were collected for the questionnaire in Flemish and in French, respectively. In this paper, we summarize main results by analyzing the profile of respondents and describing their perception of forest ecosystem services. Through the confrontation of this perception with the current scientific knowledge and through the identification of established scientific facts unknown to the general public, we identify gaps in scientific knowledge and ways of improving communication between scientists and managers. | FORBIO: Assessment of the effects of tree species BIOdiversity on FORest ecosystem functioning’

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED [Axe_IRSTEA]TED-EPURE | International audience | Subsurface horizontal flow constructed wetlands (HFCW) and vertical flow constructed wetlands (VFCW) have been compared regarding their efficiencies on microbiological indicators removal. Seven types of HFCWs and two types of VFCWs have been monitored for several years. Fecal coliforms, E. coli, somatic coliphages and F-specific bacteriophages were analyzed in the influent and effluents of each system. All constructed wetlands monitored were planted with Phragmites australis but have different design characteristics and operation variables. All data were statistically treated (SPSS v17) in order to analyse the effect of design and operation variables on each microbiological indicator. VFCWs were more efficient than HFCWs systems when considering removal rates per surface for all the microbiological indicators (cfu or pfu removed/m2.d). Nevertheless, considering mean removal efficiencies (in log units), results did not show statistically significant differences. The hydraulic retention time was the key parameter regarding filter disinfection capacity in both types of filters. Bacterial indicators were removed at a higher rate than viral indicators.