Distribution System Indicators of Drinking Water Quality

Background and Disclaimer The USEPA is revising the Total Coliform Rule (TCR) and is considering new possible distribution system requirements as part of these revisions. As part of this process, the USEPA is publishing a series of issue papers to present available information on topics relevant to possible TCR revisions. This paper was developed as part of that effort. The objectives of the issue papers are to review the available data, information and research regarding the potential public health risks associated with the distribution system issues, and where relevant identify areas in which additional research may be warranted. The issue papers will serve as background material for EPA, expert and stakeholder discussions. The papers only present available information and do not represent Agency policy. Some of the papers were prepared by parties outside of EPA; EPA does not endorse those papers, but is providing them for information and review. Questions or comments regarding this paper may be directed to [email protected]. As discussed in the " TCR and Distribution System Issue Papers Overview, " EPA plans to assess the effectiveness of the current TCR and determine what alternative and/or additional monitoring strategies are available, and to consider revisions to the TCR with new requirements for ensuring the integrity of the distribution system. Part of this assessment entails reviewing available indicators of distribution system water quality and determining whether a potential indicator can adequately identify the failure of barriers that protect against waterborne disease. This paper compiles available information on indicators of drinking water quality within potable water distribution systems. The indicators include microbial and non-microbial parameters for which sample collection and analyses could be performed to identify existing or potential problems, as well as other methods or tools that may similarly function as problem indicators. Distribution-related problems for which indicators are evaluated are based on the priority issues identified for the Distribution System White Papers developed for the Total Coliform Review potential revisions (USEPA, 2006). For the purposes of this paper, the distribution system-related problems for which indicators might be used were divided into three categories that represent the range or degree of severity associated with problem outcomes including: 1) Indicators of Pathways that Breach Distribution System Integrity 2) Indicators of Distribution System Contamination 3) Indicators of Public Health Risk The descriptions of each indicator were compiled by reviewing the primary literature available in online databases, such as Medline and Biological …