Security Approaches for Water Distribution Systems in the Next Decade

Edward McBean and Hailiang Shen

ABSTRACT

Security approaches to protect water within the water distribution system itself have assumed an entire new set of directions over the last three decades. Recognition of the formation of trihalomethanes with their cancer-causing illness was an initiating dimension, but was closely followed by the realization that water infrastructure is rapidly deteriorating, and other dimensions including increased awareness of the frequency of cross-connections and backflow failures, along with the potential for intentional actions (both malevolent and terrorist related), all of which can impact the safety of water within the distribution system. The net result of all the aforementioned is that much more attention is now being given to concerns with water security for water within the distribution system.

In response, because water within the distribution system is beyond the treatment barrier, a series of activities are being intensively scrutinized, but of concern is the maturity of some of these approaches. Strategies are now dealing with the efficiency of a contaminant warning system, and components such as real-time sensor events detection, sensor network design, and contaminant source identification (CSI). Real-time event detection methods exist but the false-positive rates associated with monitoring technologies continue to be a huge issue, and the costs for intensive efforts for real-time monitoring are shown to be severely limiting for water utilities. Acceptable sensor network design and CSI systems require accurate hydraulic and water quality models, making the real-time calibration essential, but huge issues exist in data collection and the associated costs are substantial. The designs have multiple objectives, and the key factor - number of sensors (reflecting the costs) – must be rationalized since the costs are high. CSI approaches rely on conservative water quality models, since it is infeasible to predict the type of intruded contaminant(s). Accordingly, the determination of water quality reaction parameters will inevitably result in false positives in the identification; accordingly, a problem is how to decrease the false positive rate to enhance the reliability of warning systems.

The paper reviews the various approaches being used in attempts to provide secure water supply. The paper focuses on what is currently feasible, reflecting their current limitations. The results will show that computing power no longer represents the limitations to providing the security backup, but what remains are major issues associated with the monitoring equipment, event detection algorithms, data available (e.g. nodal demand), and hydraulic and water quality models, which can be realistically made available for the tasks at hand. The near-term opportunities are being investigated, as a means to improve the status quo.


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