Authors:
Poulin, Annie and Poulin, Annie and Mailhot, Alain and Mailhot, Alain and Grondin, Patrice and Grondin, Patrice and Delorme, L. D. and Delorme, Louis and Villeneuve, JeanĪ²ā¬ĀPierre and Villeneuve, Jean-Pierre
Abstract:
With emerging security issues, drinking water utilities are facing new challenges. New security strategies and emergency response plans should be implemented to face a range of possible threats. While not the most likely, drinking water contamination may be the most worrying in terms of public health, socio-economic and psychological impacts. In many previous studies, hydraulic and water quality simulation tools have been used to address security issues related to contamination. However, to our knowledge, no studies have yet focused on the elaboration of a strategy defining the field operations to implement, after contamination has been detected, to protect public health. This paper presents ongoing work defining an operational strategy based on optimizing a sequence of field operations. Three main objectives were defined in the context of this research project: 1) minimize the risk that contaminated water is consumed; 2) identify the valves to be closed to safely contain the contaminated water and proceed, as quickly as possible, to isolation operations; 3) define a set of operations to efficiently flush contaminated water from the network to quickly and safely return to a normal operation. It is assumed that a utility has installed a Contamination Early Warning System (CEWS) to physically secure the distribution network, and that a reliable public notification system is in place as well. A simplified version of a static sensor placement optimization model is used to locate contaminant detectors. Depending on which detector gives the first alarm, a potentially contaminated zone can be delineated and the spatial expansion of this zone can be traced through time. A heuristic algorithm based on a set of pragmatic, operational and safety rules to isolate contaminated zones is introduced. Considering simultaneous field manipulations and no limit on the number of response teams (2 persons, 1 specialized vehicle), a solution is sought to ensure that every operation required for isolation can be executed before contamination reaches isolation valves. An application example is presented for the small network of Valcourt (Quebec, Canada). Although the current work is based on simplifying assumptions regarding hydraulic and contaminant transport simulation, our isolation algorithm remains general and straightforward enough to be implemented under various modeling schemes. Future works will address the operational issues related to flushing contaminated water from previously isolated zones. This paper was presented at the 8th Annual Water Distribution Systems Analysis Symposium which was held with the generous support of Awwa Research Foundation (AwwaRF).
