What are colloids in the context of water treatment?

Colloids in the context of water treatment refer to very small, finely divided solids that remain dispersed in a liquid, primarily due to electrical charge. Their size typically ranges from 1 nanometer to 1 micron, which is larger than a true solution's solute particles but smaller than the particles that settle out under gravity. The presence of surface charges on colloidal particles prevents them from clumping together and settling, allowing them to remain suspended in the water.

In water treatment, understanding colloids is crucial because they can significantly affect water quality. They can trap bacteria and other pathogens, interfere with disinfection processes, and contribute to the turbidity of the water. This makes it essential for treatment processes to include methods to remove or coagulate colloids to ensure clean and safe drinking water.

Other options do not accurately describe colloids. For instance, large solid particles that settle quickly pertain to sediment rather than colloids, and non-dissolved particles that float on water would be more characteristic of floc rather than colloids. Liquid solutions with large molecules describe a different category entirely, such as colloidal solutions, which doesn’t fit the definition of colloids in water treatment.