Towards a better knowledge and management of infiltration and exfiltration in sewer systems: the APUSS project

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 nor exfiltration. Infiltration of groundwater is particularly detrimental to treatment plant efficiency, while exfiltration of wastewater can lead to groundwater contamination. During the period 2001-2004, the European research project APUSS (Assessing infiltration and exfiltration on the Performance of Urban Sewer Systems) was devoted to sewer infiltration and exfiltration questions. It was structured on three main Work Areas dealing respectively with i) the development of new measurement methods based on tracer experiments and accounting for detailed uncertainty analyses, ii) the implementation of models and software tools to integrate structural and experimental data and to facilitate data display, operational management and decision making process and iii) the integration of economic and operational questions by means of costs estimation, economic valuation, performance indicators and multi-criteria methods applied to investment/rehabilitation strategies. This overview paper describes synthetically the objectives, methods and main achievements for each Work Area. References to both antecedent and companion papers are given for results and more detailed information.