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How does activated-carbon filtering remove some water contaminants?

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Diagram of a water treatment plant showing the process from water inlet through mixing, coagulation, flocculation, settling, filtering, chemical treatment with chlorine, storage, and high-lift pumping to the distribution system. — water purification Water from inlets located in the water supply, such as a lake, is sent to be mixed, coagulated, and flocculated and is then sent to the waterworks for purification by filtering and chemical treatment. After being treated, the water is pumped into water mains for storage or distribution.

Activated-carbon filtering removes contaminants from water primarily through the process of adsorption.1

Unlike absorption, which involves one substance being taken into the volume of another, adsorption is a surface phenomenon where molecules are attracted to and held on the surface of a solid. Activated carbon is highly porous and possesses an extremely high ratio of surface area to volume, providing ample space for impurities to attach.2

In the context of public health and water treatment, this method is particularly effective at removing dissolved organic substances that can cause unpleasant tastes, odors, or colors in drinking water. When the carbon becomes saturated with these impurities, it can be cleaned or reactivated by heating it to a high temperature in a specialized furnace. This process is utilized both in large-scale water treatment systems and as an alternative purification method in areas lacking centralized infrastructure.13