AWWA JAW71987

It has become generally accepted that water quality can deteriorate in a distribution system through microbiological and chemical reactions in the bulk phase and/or at the pipe wall. A serious aspect of water quality deterioration in a network is the loss of the disinfectant residual that can weaken the barrier against microbial contamination. The purpose of this study was to address the loss of free chlorine in corroded metal and polyvinyl chloride (PVC) pipes subject to changes in velocity. The study demonstrated that in older unlined metal pipes, chlorine residuals disappear rapidly with increased velocity but remain stable in PVC pipe. It is clear from the experiments reported in this article that there are differences between the wall demand characteristics of unlined metallic and PVC pipe and that these differences have regulatory implications. The authors also found that although distribution system modeling is an important activity that should be maintained and even expanded, no model is perfect and utilities must maintain a carefully constructed calibration program when models are used.

Includes 30 references, tables, figures.