What type of primary contaminant includes small particles suspended in water?

The primary contaminant that includes small particles suspended in water is turbidity. Turbidity refers to the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye. This can include a variety of substances, such as silt, clay, organic matter, and microorganisms, which can interfere with the penetration of light through the water. High turbidity levels can indicate poor water quality and can shield harmful pathogens from disinfection processes, hence it is critical to monitor and control turbidity in water treatment processes.

In contrast, microbial contaminants involve bacteria, viruses, and other pathogens; organic contaminants pertain to carbon-based molecules like pesticides and pharmaceuticals; and inorganic contaminants consist of minerals or metals like lead and nitrates. While each of these types represents different categories of water contaminants, turbidity specifically targets the physical property of suspended particulates in water.