Routine monitoring of the microbial quality of treated piped drinking water supplies is primarily carried out using which test?

Introduction / Context:
Public health surveillance of water supplies relies on indicator organisms that signal fecal contamination and treatment efficacy. Direct routine testing for every pathogen is impractical; instead, coliform bacteria (particularly E. coli) serve as reliable indicators of sanitary quality in distribution systems.

Given Data / Assumptions:

• Treated, piped drinking water supply under routine monitoring.
• Indicator approach preferred over exhaustive pathogen identification.
• Laboratory capacity typical of municipal water quality programs.

Concept / Approach:
The Coliform MPN test estimates the most probable number of coliform organisms per 100 mL using serial dilution and fermentation tubes or membrane filtration counts. The presence/absence and counts of coliforms correlate with the likelihood of fecal contamination and disinfection failures. Heterotrophic plate counts are supplementary process indicators but do not directly indicate fecal pollution.

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