AWWA WQTC65781

The primary goal of a Contaminant Warning System (CWS) is to quickly detect a possible contaminationincident within a water distribution system so that action can be taken to minimize consequences. TheUS Environmental Protection Agency's (USEPA's) Water Security (WS) Initiative (formerly WaterSentinel) seeks to design, deploy, and evaluatea model CWS. The WS-CWS model combines multiple monitoring and surveillance strategies includingonline water quality monitoring, sampling and analysis, enhanced security monitoring, consumercomplaint surveillance, and public health surveillance.Online water quality (WQ) monitoring is the focus of the evaluation described in this paper. Thiscomponent consists of monitoring stations placed strategically throughout the water distribution systemthat contain sensors that continuously monitor various WQ parameters. It is impractical to install sensorsthat directly monitor for each possible contaminant because there are simply too many potentialcontaminants and a lack of sensor technologies to cover even a fraction of these contaminants. Therefore,under the WS-CWS design, contamination is detected indirectly by monitoring standard WQparameters in an attempt to identify water quality anomalies, or deviations from an established waterquality base state, that might be indicative of contamination.Anomalies in one or more WQ parameters can provide early warning of contamination, but only if theycan be picked out of noisy background data. Distribution system water quality data is naturally variableand largely unpredictable, and the imperfect sensor hardware that collects the data adds to the uncertainty.Therefore, the online monitoring component of WS-CWS relies upon event detection algorithms todistinguish between normal variations in water quality and changes in water quality triggered byabnormal conditions. In this paper, event detection system (EDS) refers to a software package thatincludes event detection algorithm(s). In practice, EDS tools will work in near real-time by receiving datavia remote telemetry through the water utility's supervisory control and data acquisition (SCADA)system, perform an analysis in near real-time, and return a result (i.e., either sound an alarm or not, orindicate the probability of an event on an operator's screen). While such abnormality detection tools havebeen used in other applications, there is little experience applying them to detection of anomalies indrinking water systems.The WS-CWS pilot continues to provide a unique opportunity to collect data necessary for a rigorousevaluation of EDS tools. This paper describes the evaluation approach developed as part of the WSInitiative including the experimental matrix and performance measures used, the two EDS tools evaluatedand deployed at the WS-CWS pilot utility, and a portion of the results of the evaluation conducted in theSpring of 2007. The primary objectives of this evaluation included selecting one or more EDS tool fordeployment at the pilot utility, establishing a process for evaluating EDS tools which mimics normalutility operating conditions, improving understanding of EDS tool capabilities, and quantifying theperformance of EDS tools. Includes 11 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

20

File Size:

1 file , 550 KB