Chemistry – Chemistry of the environment - Water | e-Consult

The treatment of domestic water typically begins with sedimentation. Raw water often contains suspended solids such as clay, silt, and organic matter. In sedimentation, the water is allowed to stand in large tanks. Gravity causes the heavier particles to settle to the bottom of the tank, forming a sludge layer. This process removes a significant portion of the solid impurities.

Following sedimentation, the water then undergoes filtration. The clarified water from the sedimentation tank is passed through a filter, typically consisting of layers of sand, gravel, and charcoal. These layers act as a physical barrier, trapping any remaining suspended solids that were not removed during sedimentation. The water is forced through the filter, and the solids are retained within the filter media. This results in clearer, cleaner water. The purpose of both sedimentation and filtration is to remove particulate matter, improving the water's clarity and making it safer for subsequent treatment stages.