What type of organisms are usually used as indicators of water quality?

Non-pathogenic bacteria are often used as indicators of water quality because they can provide information about the overall microbiological health of a water source without posing a direct threat to human health. These indicator organisms are typically abundant, easily detected, and their presence can correlate with the potential presence of pathogenic microorganisms.

By monitoring the levels of non-pathogenic bacteria, water operators can infer the effectiveness of water treatment processes and the level of contamination in the water. Coliform bacteria, for example, are commonly used for this purpose. Their presence suggests that fecal contamination may have occurred, and they serve as a warning sign to investigate further for potentially harmful pathogens.

In contrast, pathogenic organisms, while also relevant to water quality, are not typically used as indicators due to their potential health risks and lower abundance in comparison. Similarly, algae and fungi play different roles in ecosystem health rather than serving as straightforward indicators of water safety. Heavy metal organisms is not a standard term and does not accurately reflect the types of indicators used to assess water quality. Non-pathogenic bacteria stand out as a reliable, established method for monitoring and ensuring the safety of drinking water supplies.