What term refers to unwanted substances that require removal from water?

The term "contaminants" refers to unwanted substances that require removal from water. Contaminants can include a wide variety of harmful materials, such as chemicals, pathogens, heavy metals, and biological organisms that can compromise water quality and pose risks to human health and the environment.

Understanding the general classification of water pollutants is key to environmental health. While microorganisms might be one category of contaminants, they do not encompass all unwanted substances. Nutrients, such as nitrogen and phosphorus, are important for the ecosystem; however, in excess, they can lead to problems like algal blooms but are still categorized differently than general contaminants. Solids refer specifically to particulate matter or sediments within water, which can also be a form of contamination, but do not represent the broader spectrum of unwanted substances that may require treatment or removal.

In summary, contaminants is the most comprehensive and accurate term when identifying unwanted substances that need to be managed to ensure safe and clean water.