In the bacteriological analysis of water, a positive completed test is definite proof that the sample of water:

A positive completed test in the bacteriological analysis of water indicates the presence of coliform bacteria. Coliform bacteria are a group of bacteria found in the environment, human and animal feces, and in soil and vegetation. The detection of coliforms suggests that there may be a pathway for pathogens to enter the water supply, but it does not prove the presence of pathogens themselves.

While coliforms are an indicator of microbial contamination, they do not specifically identify the sources of pollution or confirm the presence of harmful pathogens. Therefore, a sample that tests positive for coliform bacteria may be unsafe to drink, but it does not definitively indicate that it contains enteric pathogens or that it was polluted with human fecal material specifically.

The importance of coliform testing lies in assessing water safety because the presence of these bacteria raises a concern about potential contamination and the possibility of pathogens. Therefore, a positive result indicates a reason for further investigation and potential treatment of the water to ensure its safety for consumption.