Securing water distribution systems using online contamination monitoring

The events of September 11, 2001 in the United States have brought to the fore the problem of drinking water distribution systems security. As a water distribution system is spatially diverse, limiting physical access to all components is practically impossible. Deliberate intrusions of contaminants directly into tanks, treatment plants, or through connecting devices is considered one of the most serious terrorist threats. An effective means of reducing this threat is online contamination monitoring. This paper extends previous work of the writers for optimal allocation of monitoring stations to secure drinking water distribution systems against deliberate contamination intrusions. The current methodology takes explicitly into account the randomness of the flow rate of the injected pollutants, the randomness in consumer's demands, and the detection sensitivity and response time of the monitoring stations. The objective is to determine the optimal location of a set of monitoring stations aimed at detecting deliberate external terrorist hazard intrusions through water distribution system nodes: sources, tanks, treatment plant intakes, consumers-subject to extended period hydraulic demands and water quality conditions, and a maximum volume of polluted water exposure to the public at a concentration higher than a minimum hazard level. The methodology is implemented in a noncommercial program entitled optiMQ-S and demonstrated on EPANET Example 3.