Caractérisation et estimation des flux de substances prioritaires dans les rejets urbains par temps de pluie sur deux bassins versants expérimentaux

La réduction des rejets urbains par temps de pluie (RUTP) est devenue un enjeu majeur pour de nombreuses collectivités dans le but d'atteindre les objectifs de qualité des masses d'eau superficielles et souterraines fixés par la Directive Cadre européenne sur l'Eau (DCE 2000/60/CE). Alors que les concentrations et les charges des polluants classiques (MES, DBO, DCO, nutriments ... ) dans les RUTP sont bien documentées, très peu d'informations sont disponibles sur la présence, les concentrations et les charges des substances prioritaires dans ces rejets. Le projet ESPRIT (Évaluation des Substances Prioritaires dans les Rejets Inhérents au Temps de pluie) a pour objectif d'identifier, d'évaluer, de caractériser puis de modéliser les flux de substances prioritaires dans les RUTP dans les systèmes d'assainissement unitaire et séparatif en tenant compte de leurs différentes origines. Deux sites expérimentaux ont été choisis pour les campagnes de mesure: Ecully (résidentiel, réseau unitaire) et Chassieu (industriel, réseau séparatif). Les concentrations moyennes événementielles à l'exutoire par temps de pluie, les concentrations moyennes journalières par temps sec dans le cas d'un réseau unitaire, la collecte périodique des dépôts atmosphériques secs et les concentrations événementielles des eaux météoriques ont été mesurées. 26 métaux sont analysés par ICP-MS/AFS dans les phases dissoute et particulaire. Une analyse multi-résidus permet de quantifier 36 micropolluants organiques dans les phases dissoute et particulaire par GS-MS et LC-FLDMS/MS. Des analyses complémentaires sont également réalisées afin de mieux caractériser les rejets et évaluer leur traitabilité. Sur les 40 substances prioritaires de la DCE recherchés dans les RUTP, seulement 17 ont été détectées. Tous les métaux ont été quantifiés pour les deux sites pour toutes les campagnes. Sur les 36 substances organiques, seulement 13 ont des CME supérieures à la LOD, telles que diuron, atrzine et fluoranthène.The reducing urban stormwater discharges is one of the major stakes for operators of urban water systems in order to achieve quality objectives of surface and underground water established by Water Framework Directive. Whereas concentrations and loads of traditional pollutants (suspended solids, BOD, COD, nutriments ...) in stormwater discharges are well documented since three decades, less information is available on the presence, the pathways, the concentrations and the loads of priority pollutants in these effluents. The objectives of the ESPRIT collaborative project are to identify, evaluate, characterize and later on model the fluxes of priority substances in urban stormwater, for bath combined and separate sewer systems, tacking out different sources. Two experimental sites have been selected ln Lyon, France for monitoring campaigns: Ecully (residential, combined sewer system) and Chassieu (industrial, separate stormwater system). The monitoring campaigns included storm event mean concentrations (EMC), dry weather daily and hourly mean concentrations in wastewater for the combined sewer, the periodic collection of dry atmospheric deposits and event sam pies of rainwater. 26 metals are analysed by ICP-MS/AFS in dissolved and particulate phases. A new multi-residues analytical method is used to quantify 3 organic micro-pollutants in the dissolved phase and in the particulate phase by GS-MS and LC-FLD-MS/MS. On 40 priority pollutants of WFD investigated in stormwater discharges, only 17 pollutants have been detected. Ali metals were present in bath sites for all rain event campaigns. On 36 organic pollutants, only 13 were above the LOD, like diuron, atrazine and fluoranthène.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

Accumulated sediments in a retention/detention basin: What about the contamination in terms of emerging pollutants?

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Multi-Level Approach of the Ecotoxicological Impact of a Combined Sewer Overflow on a Peri-Urban Stream

International audienceIn periurban zones, urban wet weather discharges have been recognized as the most significant vector of pollution in aquatic environments. The discharge of this water without treatment into the aquatic environment could present an ecotoxicological risk for biocenosis. The aim of the INVASION project is to assess the potential ecotoxicological im- pact of a combined sewer overflow (CSO) on a peri-urban stream. A comparative study between upstream and down- stream areas of the CSO allowed observing significant effects of this overflow on the river. We studied three layers of stream: surface water, benthic layer and hyporheic layer. To characterize the potential ecotoxicological risk of water and sediments, we used a battery of 4 bioassays: Daphnia magna, Vibrio fischeri, Brachionus calyciflorus and Hetero- cypris incongruens. In parallel, we measured the physico-chemical parameters: ammonium ( NH ), chromium (Cr), 4 copper (Cu) and lead (Pb). An ecological risk is greatest for the hyporheic zone in downstream river, particularly for the solid phase. These results corroborated with the physico-chemical data obtained

Dynamics of toxicity within different compartments of a peri-urban river subject to combined sewer overflow discharges

International audienceCombined Sewer Overflows (CSO) in small pen-urban streams and rivers are potentially toxic for their biocenosis. Improving the management of CSO discharges requires better knowledge of their dynamics and toxicity. In view to characterizing this toxicity, we sampled the different compartments (benthic and hyporheic zone) of a pen-urban stream located near the city of Lyon in France. The samples were taken at different distances from a CSO and at three period characteristic of different hydrological conditions. Their toxic effects were assessed by bioassays on the dissolved fraction (D. magna, V. fished and B. calyciflorus bioassays) and on the particle fraction (V. fished and H. incongruens bioassays). The results highlighted significant toxicity of the particulate fraction for the benthic and hyporheic samples, in particular downstream of the CSO, but with high spatio-temporal variability. This variability can first be attributed to the variability of CSO discharge sampling as a function of season and rainfall, and the dynamics of polluted particles (trapping of transported particles in infiltration zones, mobilization during floods). These parameters play a fundamental role in the distribution of pollutants according to the geomorphology of stream facies. Regarding dissolved pollutants, the chemical exchanges taking place at the "water-sediment" interface trigger the transfer of pollutants from one phase to another, after which the dispersion of these pollutants is governed by hydraulic flows. Finally, critical zones and periods are identified for the pen-urban river toxicity studied: benthic sediments under mean flow downstream: hyporheic sediments after a storm event downstream, close to the CSO. Recommendations are made on the basis of the knowledge obtained to optimize the management of these discharges

3D numerical modelling of resuspension and remobilization of sediments in a stormwater detention basin

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