Coliforms are primarily used as indicators of what type of contamination?

Coliforms are primarily used as indicators of fecal contamination because they are a group of bacteria that are commonly found in the intestines of warm-blooded animals, including humans. The presence of coliforms in water suggests that fecal matter has entered the water source, which may carry harmful pathogens associated with diseases. Testing for coliforms, particularly Escherichia coli (E. coli), provides a reliable method to assess the microbiological quality of water and indicates a potential risk to human health from waterborne diseases.

In contrast, other types of contamination, such as chemical contamination, heavy metal pollution, and nutrient enrichment, do not typically involve the presence of coliforms. Chemical contamination pertains to synthetic substances and their effects, heavy metal pollution involves toxic metals that can be present in water and sediment, and nutrient enrichment refers to an increase in nutrients like nitrogen and phosphorus, which can lead to algal blooms but not directly point to fecal contamination. Therefore, the utility of coliforms as indicators specifically highlights their role in identifying fecal contamination in water sources.