Which of the following is NOT a type of pathogen found in wastewater?

The correct choice identifies heavy metals as substances that are not classified as pathogens found in wastewater. Bacteria, viruses, and protozoa are all microorganisms that can cause diseases and are commonly present in wastewater. They are considered pathogens due to their ability to infect humans and animals, leading to health risks if exposed to untreated wastewater.

Heavy metals, on the other hand, are elements such as lead, mercury, or cadmium, which can contaminate water sources but do not fit the definition of pathogens. They are toxic substances that can harm aquatic life and pose serious health risks due to their persistence in the environment, but they do not possess biological activity to cause infections like bacteria or viruses do.

Therefore, recognizing heavy metals as non-pathogenic helps to differentiate between various contaminants in wastewater and underscores the need for different treatment approaches for managing biological pathogens versus chemical pollutants.