What is the primary indicator of fecal contamination in drinking water?

The primary indicator of fecal contamination in drinking water is E. coli. This bacterium specifically originates from the intestines of warm-blooded animals, and its presence in water indicates recent fecal contamination. E. coli serves as a reliable marker because it is specifically associated with fecal material, unlike other microorganisms that may not directly correlate to fecal sources or may be found in the environment independently of fecal contamination.

While Clostridium perfringens is also an indicator of fecal pollution and can be used to assess water quality, it is not as specific to fecal contamination as E. coli. Salmonella, generally associated with foodborne illness, is less common as a sole indicator since it may not be present in all situations of fecal contamination. Staphylococcus aureus is often related to skin and respiratory infections rather than fecal contamination and is not commonly used as a water quality indicator.

Therefore, the focus on E. coli as the primary indicator stems from its specificity and the significant role it plays in identifying the presence of fecal matter in drinking water sources, making it critical for public health safety assessments.