What is a common indicator of the presence of pathogens in water?

Coliform bacteria serve as an important indicator of the presence of pathogens in water because they are commonly found in the intestines of warm-blooded animals and indicate fecal contamination. The detection of coliforms in water suggests that harmful microorganisms, including viruses and bacteria that can cause disease, may also be present.

E. coli, a specific type of coliform bacteria, is often used in more specific assessments of fecal contamination. While it is a critical indicator of recent contamination and pathogen presence, the broader category of coliform bacteria is generally used as a standard gauge in water quality testing due to its prevalence and the ease of its detection.

Chlorine residual and pH levels do not provide direct information regarding pathogen presence. Chlorine is a disinfectant used to kill pathogens in treated water, and measuring its residual helps assess disinfection effectiveness rather than pathogen detection. Similarly, pH levels relate to the acidity or alkalinity of the water but offer no insight into microorganism content or the potential risk of disease. Therefore, coliform bacteria remain the established common indicator for gauging pathogen risk in water bodies.