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USE OF NETWORK MODELS FOR ESTIMATING EXPOSURE OF CONSUMERS TO CONTAMINANTS IN DRINKING WATER DISTRIBUTION SYSTEMS
Citation:
GRAYMAN, W. M., S. PANGULURI, L. M. GARNER, Y. LEE, AND R. M. CLARK. USE OF NETWORK MODELS FOR ESTIMATING EXPOSURE OF CONSUMERS TO CONTAMINANTS IN DRINKING WATER DISTRIBUTION SYSTEMS. Presented at 2005 AWWA Water Security Congress, Oklahoma, OK, April 10 - 12, 2005.
Impact/Purpose:
to present information
Description:
The presence of contaminants in a drinking water distribution system can result in exposure of consumers to contaminated water. Whether the contaminants result from waterborne outbreaks that accidentally enter the system or through purposeful acts, the movement of the resulting contaminant through the distribution system can be quite complex. The resulting exposure of water consumers to a contaminant will be dependent on the duration and concentration of the contaminant reaching the household water service line, and consumer patterns of ingestion, inhalation, and dermal sorption. Calculation of exposures depends upon the stochastic nature of demands at the household level. Water distribution system models provide a mechanism for simulating the hydraulic and water quality behavior in water distribution systems and predicting the level of exposure that customers might face. However, in order to have confidence in the model results, the models must be properly formulated and calibrated. Generally both the level of spatial and temporal detail and the degree of calibration required for a model used in simulating contaminant movement and determining exposures, are more stringent than required for most classical uses of network models such as master planning and fire flow analysis. A case study will be presented that demonstrates the application of a water distribution system model in order to trace contaminant movement through a system. In this study, a food grade tracer (i.e., calcium chloride) commonly used in water distribution system studies, was employed. The tracer not only simulates contaminant movement through a distribution system but also helps in calibrating and validating the model. Following the introduction of the tracer, the resulting concentration was measured over time at various locations as it moved through the system. This paper will provide information and guidance to water utilities on planning and conducting similar tracer studies in drinking water distribution systems and demonstrate the use of the resulting model in exposure calculations.