Measuring and Modeling Chlorine Propagation in Water Distribution Systems

Abstract

Until recently most emphasis on implementing Maximum Contaminant Levels (MCLs) under the Safe Drinking Water Act and its Amendments (SDWAA) has been focused on drinking water as it leaves the treatment plant. However, the SDWAA has been interpreted as requiring that its MCLs must be met at the consumer's tap. This interpretation has forced consideration of the drinking‐water distribution system when measuring and monitoring contaminants for SDWAA compliance. It is increasingly apparent that water quality can undergo significant deterioration between the treatment plant and the consumer's tap. A field study conducted in conjunction with the South Central Connecticut Regional Water Authority using a contaminant propagation model demonstrated long residence times in one of its service areas, which suggested potential difficulties in maintaining chlorine residuals throughout the system. A follow‐up study verified that maintaining residuals is difficult and demonstrated that a simple first‐order decay model associated with modeling chlorine residuals is inadequate.