Treatment of the Public Water Supply

The process of treating public water supply commences with screening, which is meant to remove large debris such as leaves and twigs.
Following screening, a process known as sedimentation takes place, where solid particles settle at the bottom of a sedimentation tank due to the action of gravity.
Flocculation is the next step, where chemicals, typically aluminium sulphate (alum), are added to the water. This causes small particles to clump together into larger, more easily removable, flocs.
Once flocculation happens, the water goes through a second sedimentation process to remove the flocs.
The water is then filtered to remove smaller particles which may have escaped the previous steps. This process typically uses layers of sand and gravel.
Chlorination is the next vital process. Chlorine is added as a disinfectant to kill or inactivate harmful pathogens that could cause serious illnesses.
The treated water is then stored in large reservoirs before being pumped to homes, schools, and businesses.
It is important to note that in some cases, water may also be fluoridated to enhance dental health, or pH adjustment may be done to prevent corrosion in the supply pipe network.
Different sources of water (e.g., river, groundwater, lakes) can influence the type of contaminants present, thus they might require different treatments.
Notably, the water treatment process is routinely monitored and tested for various parameters to assure its safety and quality.
It is important to understand these processes as they show the significance of chemistry in our daily life, specifically in its role in ensuring our water is safe to drink. Understanding the treatment of the public water supply is a key part of the Water unit of your Chemistry course.