Many water treatment plants use a combination of coagulation, sedimentation, filtration and disinfection to provide clean, safe drinking water to the public. Worldwide, a combination of coagulation, sedimentation and filtration is the most widely applied water treatment technology, and has been used since the early 20th century.
In the Terai region of Nepal, many tube wells - a major source of drinking water - have tested positive for arsenic. The arsenic occurs naturally in sediments from the Himalayas. Levels higher than 600 parts per billion have been detected (the United States Environmental Protection Agency sets a standard for arsenic in drinking water at 10 parts per billion).
The most common water treatment tool used in homes on the rural prairie is granular activated carbon (GAC) filtration. This is a treatment technique that functions by removing particles and dissolved organic material (for example: colour), and it should generate water that is better for human consumption.