What type of microorganisms can be harmful and typically need to be removed from water?

Bacteria are indeed a type of microorganism that can be harmful and often need to be removed from water due to their potential to cause diseases. Many pathogenic bacteria such as Escherichia coli, Salmonella, and Legionella can be present in contaminated water supplies and can lead to serious health issues, including gastrointestinal infections, respiratory infections, and other ailments.

Water treatment processes often focus on the removal or inactivation of bacteria to ensure that drinking water is safe and free from these harmful pathogens. Effective methods of removing bacteria include filtration, chlorination, and UV disinfection, which are commonly employed in municipal water treatment systems.

While viruses, fungi, and protozoa can also pose health risks in water, bacteria are often the most emphasized in environmental health practices because of their prevalence and the acute health effects they can cause when ingested through contaminated water.