Ontario Operator-in-Training (OIT) Practice Exam

Which of the following is a source of pathogenic microorganisms?

1. Well-treated sewage

2. Stormwater runoff

3. Tap water

4. Filtered water

The correct answer is: Stormwater runoff

Stormwater runoff is a significant source of pathogenic microorganisms because it can collect contaminants as it flows over surfaces such as roads, parking lots, and agricultural fields. This runoff can include bacteria, viruses, and protozoa that originate from various sources, including animal waste, agricultural practices, and urban pollution. When stormwater drains into water bodies or infiltrates into groundwater, it can introduce these pathogens into the environment, posing a risk to public health and water quality. In contrast, well-treated sewage is subject to processes designed to reduce pathogens, making it less likely to contain harmful microorganisms when properly treated. Tap water and filtered water typically undergo rigorous purification processes to eliminate pathogens, making them generally safe for consumption. As such, stormwater runoff stands out as a clear source of pathogenic microorganisms due to its ability to accumulate pollutants from a wide range of sources prior to entering water systems.