Which of the following is a parasite and microbiological contaminant?

Giardia is a well-known parasite and microbiological contaminant that can affect water supplies. It is a microscopic protozoan that causes giardiasis, which is an intestinal infection. Giardia is typically transmitted through contaminated water sources and can survive in water for extended periods. This organism is particularly relevant in discussions about water quality and safety because it can lead to diarrhea and other gastrointestinal symptoms in humans.

In the context of drinking water, understanding the presence and implications of Giardia is crucial for water treatment and distribution operators, as it highlights the need for proper filtration and disinfection processes to ensure safe drinking water for the public.