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Definitions of Water Treatment

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Modern water treatment, in general, relies on several key processes: dilution, coagulation and flocculation, settling, filtration, disinfection and other chemical processes.


The Centers for Disease Control and Prevention (CDC) report that drinking water sources are subject to contamination and require appropriate treatment to remove disease-causing agents. Public drinking water systems use various methods of water treatment to provide safe drinking water for their communities. Common steps in modern water treatment include:

Coagulation and Flocculation

Often the first steps in water treatment, chemicals with a positive charge are added to the water. The positive charge of these chemicals neutralizes the negative charge of dirt and other dissolved particles in the water. When this occurs, the particles bind with the chemicals and form larger particles, called floc.


Floc settles to the bottom of the water supply, due to its weight. This settling process is called sedimentation.


Once the floc has settled to the bottom of the water supply, the clear water on top will pass through filters of varying compositions (sand, gravel, and charcoal) and pore sizes in order to remove dissolved particles, such as dust, parasites, bacteria, viruses and chemicals.


After the water has been filtered, a disinfectant (for example, chlorine, chloramine) may be added in order to kill any remaining parasites, bacteria, and viruses, and to protect the water from germs when it is piped to homes and businesses.

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