Under the Revised Total Coliform Rule, which two terms describe the indicator used to assess potential contamination pathways into the distribution system?

• A. Fecal coliform and total coliform
• B. Coliform and total coliform
• C. Coliform and Escherichia coli
• D. Total coliform and nitrates

Answer: (B)

The indicator used to assess potential contamination pathways in the distribution system is described by two terms: coliform and total coliform. Coliforms are a broad group of bacteria whose presence can indicate a possible pathway for contamination, while total coliforms are the specific subset used as the routine indicator in the Revised Total Coliform Rule. This combination signals whether there may be system integrity issues that could allow contaminants to enter the distribution network. Fecal coliforms or E. coli are more specific indicators of fecal contamination and are not the routine distribution-system pathway indicator under RTCR, and nitrates are a chemical parameter, not a bacterial indicator.