Which microorganisms are specifically targeted by the SWTR?

The Surface Water Treatment Rule (SWTR) is a regulation that aims to ensure the safety of drinking water sourced from surface waters. It specifically focuses on the treatment and removal of certain pathogenic microorganisms that can be harmful to human health. Among the options provided, the correct answer highlights Giardia, Legionella, and Cryptosporidium as the microorganisms specifically targeted by the SWTR.

Giardia and Cryptosporidium are protozoan parasites that can cause gastrointestinal illness and are resistant to chlorination, making them particularly significant in discussions of water treatment and public health risks associated with untreated drinking water. The SWTR mandates filtration and disinfection processes to significantly reduce or eliminate these pathogens from treated drinking water.

Legionella, while primarily associated with water systems and not specifically categorized under the same group as the other two protozoans, is a concern related to biofilms and water stagnation in distribution systems. Its control is critical for maintaining overall water safety, overall making treatment protocols relevant in the context of surface water.

The other options contain microorganisms that, while they may pose health risks and require monitoring in water quality, are not specifically emphasized within the constraints of the SWTR. For example, E. coli, Salmonella, and Shigella (first