Résumé des résultats (Abstract)
(Allemand)
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Short summary:
Sewer systems constitute a very significant patrimony in European cities. Their structural quality and functional efficiency are key parameters to guarantee the transfer of domestic and trade wastewater to treatment plants without infiltration or exfiltration. Infiltration of groundwater is particularly detrimental to treatment plant efficiency, while exfiltration of wastewater can lead to groundwater contamination. Both problems are critical on a long term basis for sustainable urban water management. This resarch project, associating universities, SMEs and municipalities in 7 European countries, will develop new methods and techniques to assess and quantify infiltration and exfiltration in sewer systems. The methods will be tested and validated in different sewer systems, from local to the whole catchment scale. Associated models and tools will be proposed for scaling up and for application and end-user decision support.
Scientific objectives and approach:
In order to evaluate the performance of USS, public and private operators need appropriate methods and techniques. This research project, associating universities, SMEs and municipalities in 7 European countries, will develop new methods and techniques based on tracers (chemicals and/or natural radio-isotopes) to assess and quantify infiltration and exfiltration in sewer systems, at different space scales (from the single pipe to the whole catchment) and under different conditions (steady and dynamic groundwater levels, seasonal effects). The methods will be tested and validated in different catchments chosen in the associated cities, under various conditions. Associated models (based on conceptual approaches for both steady and dynamic groundwater conditions) and tools (GIS and data management software) will be proposed for scaling up and for application and end-user decision support.
Complementary objectives consist to develop decision supports to help end users to assess the performance of their sewer systems and to choose investment strategies accounting for economic value and necessary data
Problems to be solved:
Urban sewer systems (USS) constitute a very significant patrimony in European cities. Their structural quality and functional efficiency are key parameters to guarantee the transfer of domestic and trade wastewater to treatment plants without infiltration nor exfiltration. Infiltration of groundwater is particularly detrimental to treatment plant efficiency (hydraulic overloading due to the infiltrated volume of water which can reach up to 100 % of the wastewater volume in some cities, dilution of pollutant concentrations which leads to a lower pollutant removal efficiency), while exfiltration of wastewater can lead to groundwater contamination (especially where groundwater is a water resource for drinking water production). Both problems are critical on a long-term basis for sustainable urban water management and have important economic consequences for cities and sewer systems operators through the EU. The participants in the project, associated with cities and sewer operators concerned by these problems, have complementary knowledge and experiences they have decided to bring together in order to propose methods and tools to assess infiltration / exfiltration rates on more serious and scientific basis than before, and to help cities and operators to define better investment and rehabilitation strategies.
Expected Impacts:
Based on the methods, techniques and tools developed during the project, the main expected impacts should be :
- a better knowledge on urban sewer systems, in terms of infiltration and exfiltration. This should be included in the frame of a global asset management plan and also be a part of the sewer monitoring system.
- better investment and rehabilitation strategies of urban sewer systems to preserve the groundwater resource and minimise the impact on wastewater treatment plants.
- as municipalities and sewer operators are associated to the participants, they will take a part in the validation of the methods and tool and are directly interested to use them. They will also participate in the dissemination of the results during the years following the end of the project.
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