What is a common indicator of water pollution from sewage?

The presence of coliform bacteria is a widely recognized indicator of water pollution from sewage. These bacteria, which include E. coli, are normally found in the intestines of humans and warm-blooded animals. Their detection in water suggests that there has been contamination from fecal material, which is often a result of inadequate sewage treatment or pollution from septic systems. The presence of coliforms serves as a warning sign about potential pathogens that could be harmful to human health and aquatic life.

Monitoring for coliform bacteria is a standard practice in water quality testing because it provides a straightforward method to assess the microbiological safety of water sources. High levels of coliform bacteria indicate that the water may also harbor other harmful microorganisms, leading to an overall assessment of water quality and safety for recreational and drinking purposes.