AWWA RSP64388

The information presented in this paper has been developed as part of an ongoing AwwaRF Project #3116, Strategy to Manage and Respond to Total Coliform and E. coli in the Distribution System. The objective of this paper was to describe strategies used by utilities to identify causes of coliform positives and strategies used to mitigate occurrences based on a summary of case studies that have been developed for the AwwaRF project. These case studies present examples of current industry practices and also serve as examples of strategies that may be used to address microbial problems in the distribution system. Additionally, this paper presents the results of a survey conducted at an Experts Workshop on microbial source tracking tools and strategies that utilities could apply in different microbial water quality scenarios. The appropriate strategies for investigation and mitigation depend on multiple factors including the suspected cause of the microbial problem, the type of Total Coliform Rule violation or problem the system is experiencing, and system-specific factors affecting distribution system water quality. Due to the wide range of variables associated with these issues, the AwwaRF Project Team is developing a toolbox of strategies that can be used by utilities based on system-specific circumstances. Includes tables, figures.