Dynamic Water-Quality Simulation for Contaminant Intrusion Events in Distribution Systems

The design of contamination warning systems and the performance of forensic tools are dependent on the performance of the event detection algorithms (EDA). However, most current EDA evaluation approaches do not account for the actual changes of common water-quality parameters in response to a contaminant. Thus, the objective of the current study was to develop water-quality models to represent the dynamics of chlorine, hydrogen ion concentration (pH), and conductivity in response to two contaminants [potassium cyanide (KCN) and nicotine] using experimental data. For chlorine-contaminant dynamics, a two-species second-order model was used to represent the reactions between chlorine and the background dissolved organic carbon as well as the contaminant. To simulate the change in pH, an equilibrium model was used to account for various water-quality species and was coupled with the dynamic chlorine model. As for electrical conductivity (EC), a step response, which is a linear relationship to the amount of contaminant added, was used to simulate the change of EC. These water-quality dynamic models were incorporated into EPANET-MSX to more realistically simulate the responses of common water-quality parameters to a contamination event at a network scale, as well as assess current assumptions/evaluation techniques associated with risk assessment for sensor placement and EDA performance. Results demonstrated that the current EDA evaluation approaches, as well as contamination warning system (CWS) design assumptions, may not adequately represent the EDA performance under conditions likely to be observed within a distribution system.