Partenaires et organisations internationales
(Anglais)
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AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GR, HR, IE, IL, IT, LU, LV, MK, NL, NO, PL, PT, RO, RS, SE, SI, TR, UK
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Résumé des résultats (Abstract)
(Anglais)
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A modern city is a place of residence for living organisms, humans and many others. Thus, it can be itself described as the sum of the metabolism of its inhabitants, being called 'city's metabolism' or 'urban metabolism'. The idea is to investigate a city as an organism which can be studied by modelling the flows entering, accumulating and going out of the urban system. To be regarded as sustainable, the urban metabolism has to fulfill certain criteria, which cover social, economic and environmental impacts, and which avoid reducing the abilities of future generations to serve their needs as we presently serve ours. Among the different kind of flows that can be studied within the scope of urban metabolism, water flow has a crucial place, as water is one of the fundamental needs of living organisms. Recent research has shown that water in urban areas is contaminated by xenobiotics. The goal of this study was to define a set of clear and concise sustainability criteria for xenobiotics in the urban water cycle. These criteria had to be related to quantifiable indicators that are easily measured and easily communicable so that they can be used for public information. In a first step, we built a model describing the urban water cycle in Lausanne. This model combines inputs of xenobiotics through antropogenic activities (wastewater/stormwater) as well as through rainwater or drinking water. In the model, the xenobiotics may be released in surface water through wastewater treatment plants, combined sewage overflows or through stormwater. They can exit the cycle by degradation, storage in soil or in sludge from wastewater treatment plants. In a second step, we also developed a methodology to define indicators following hazard and risk assessment methods. These indicators summarize mainly the toxicity and ecotoxicity of the xenobiotics. They are defined as water quality criteria allowing sustainable protection of the aquatic ecosystem. For a specific application, we decided to focus on three groups of xenobiotics: biocides released from building materials, pharmaceuticals and xenobiotics emitted by trafic. For these groups, tracers were identified such as diclofenac for pharmaceuticals or copper for the trafic. Water quality criteria were defined for these tracers. The urban water cycle model was adapted to the three groups, which do not have similar sources and fate in the system, and validated for the tracers with field measurements. The results showed good agreement between predictions and measurements indicating that the model is suitable for describing the fate and behaviour of the xenobiotics in the urban water system. Furthermore, the model allows highlighting the main source of each xenobiotic in the system and therefore the potential of improvement to reduce the pollution, if needed. Such a model is thus an interesting tool for urban water management.
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