What is the pretreatment process used to remove gravel, sand, and silt from the raw water?

The pretreatment process used to remove gravel, sand, and silt from raw water is known as presedimentation. This process involves allowing the water to sit in a large tank or basin, where heavier particles, such as gravel and sand, settle to the bottom due to gravity. This helps to reduce the load on subsequent treatment processes, ensuring cleaner water enters the treatment system.

Presedimentation is an effective method for improving the quality of water before it undergoes further treatment, such as filtration or disinfection. It enhances the overall efficiency of the drinking water treatment process by minimizing the amount of solids that need to be removed in later stages.

In contrast, screening is primarily effective for removing larger debris like leaves and sticks rather than fine particles like silt. Preoxidation is a process used to improve the removal of certain contaminants but does not specifically target physical sediment. Microstraining targets smaller particulates, but again, it is not designed specifically for settling out larger materials like gravel and sand. Therefore, presedimentation is the most appropriate and effective process for achieving the intended removal of these materials from raw water.