What does the presence of coliform bacteria in a water distribution system indicate?

The presence of coliform bacteria in a water distribution system is a critical indicator of potential contamination by pathogenic organisms. Coliform bacteria are used as a key indicator of microbial quality in water because they are commonly found in the environment, particularly in soil and feces of warm-blooded animals. Their presence suggests that the water may have been contaminated by fecal material, which could harbor harmful pathogens that pose a health risk to consumers.

Monitoring for coliform bacteria helps ensure that the water supply is safe and that any potential breaches in the water distribution system are identified and addressed promptly. Therefore, detecting coliform bacteria serves as a warning sign for possible microbial contamination and indicates the need for further testing and corrective actions to ensure the safety of the water supply.

In contrast, the other choices refer to misleading assertions about the water's safety or characteristics. The presence of coliform does not confirm the water is safe to drink, nor does it determine if the system is properly chlorinated or if the water is hard. These aspects require separate evaluations.