Vulnerability of drinking water distribution systems to deliberate attacks, which would have major public health, economic and psychosocial consequences, is one of the main issues of concern to regulatory agencies, and water utilities. Such a network appears very vulnerable and easy to contaminate through reservoirs, back-flow… The main objective of this proposal is to limit the impact on the population of safe water privation because of contaminated networks, and to launch an appropriate response for rapidly restoring the use of the network after a deliberate contamination. Questions that will be addressed for successful coordinated response of water utilities and regulatory agencies to contamination include: •Detection of unexpected changes in water quality which could be in relation with a deliberate contamination event, •Adaptation of known analytical methods to rapidly detect specific CBRN contaminants in water and in biofilms. •Localization of the point sources of contamination and subsequently the contaminated area allowing delimitation of the corrective actions. •Decontamination procedures (efficient and realistic) of the distribution system. •Controlling the efficacy of the corrective actions by analysing the water bulk and especially the pipe walls and the deposits. •Cases studies will give the chance for the practitioners to apply on site in real conditions the selected sensors, methods, remediation technologies… It is a unique occasion to test an emergency procedure on a complicated, inaccessible, and relatively fragile system, to evaluate its feasibility at field scale, and to evaluate the difficulty to apply corrective treatments to the huge water bulk generated by the neutralisation/extraction of contaminants. The SecurEau project will therefore contribute to the European scientific excellence, to the European competitiveness and to the fight against terrorism, in accordance with the guidelines set up by the EC in the last 5 years.