What does the presence of fecal coliform or non-coliform bacteria in a water sample indicate?

• A. No contamination detected
• B. Indicates a sufficient treatment process
• C. Treatment is functioning perfectly
• D. Contamination by animals or humans

Answer: (D)

Bacteria in a water sample are used as indicators of contamination. Fecal coliforms come from the intestinal tracts of warm-blooded animals, including humans, so finding them means that fecal material has entered the water. That signals contamination by animals or humans. It’s not a sign that nothing is wrong or that the treatment is fully effective; rather, it suggests the water has been or could be contaminated and may require corrective actions, such as further testing and adjustments to disinfection or source controls. Non-coliform bacteria can be present in the environment as well, but the presence of fecal coliforms specifically points to fecal contamination, which is the primary safety concern.