What is the process of sedimentation in water treatment used for?

The process of sedimentation in water treatment is specifically designed to allow particles to settle out under gravity. When water contains suspended solids, sedimentation is an effective method to reduce the concentration of these solids by taking advantage of gravity.

In a sedimentation tank, water flows slowly, providing enough time for heavier particles to sink to the bottom. This process results in a clearer upper layer of water, while the settled solids accumulate as sediment at the bottom, which can then be removed. This method is crucial in the preliminary stages of water treatment, as it helps improve the efficiency of subsequent processes, such as filtration and disinfection.

Other choices describe different aspects of water treatment that do not accurately reflect sedimentation. Evisceration of chemical pollutants typically involves chemical treatments rather than physical settling. Filtering solids from liquid pertains more to the filtration process, which mechanically captures suspended particles instead of relying on gravitational settling. Chemically altering the composition of water generally refers to chemical treatments aimed at changing specific water chemistry rather than sedimentation. Therefore, the most fitting definition for sedimentation is its role in allowing particles to settle out under gravity.