AWWA WQTC59011

The water industry has focused predominantly on the quality of treated water and the physical condition of distribution assets when improving the quality of water at the customer's tap. However the quality of the water delivered is also affected by the time the water is retained in the different elements of the distribution network. This paper presents work which has been undertaken in the first phase of the ongoing AwwaRF research project #2769: Evaluating Retention Time to Manage Distribution System Water Quality. The paper: identifies the water quality parameters which are affected by retention time; summarizes the analysis tools available to investigate retention time problems and assesses their utilization via the results of an international survey of 23 utilities; presents methods by which retention time can be adjusted within supply systems; and, outlines a systematic approach to retention time management; The overall conclusion of the work is that retention time is an effective means of controlling some water quality parameters. However, there is a need for a structured approach to help utilities select analysis tools and control measures that are appropriate to the significance of the problem and availability of data and resources. Such an approach is being developed and tested in Phase 2 of this project. Includes 44 references, tables.