Water is one of the most essential element to life on earth. Without water no living organism can survive. Treatment of drinking water is the process of removal of contaminants from water and make it acceptable for use. The treatment process for drinking water depends on the location, type of water to be processed and the technology of the plant. Here is a standard treatment process for drinking water.
Coagulation
It is the process of removing dirt or other particles from the water. In this process, alum or polymers are added to the water to be treated. This on reaction with water forms a tiny sticky floc. This floc attracts dirt particles in the water and sticks to it and forms a large floc. This process is also called flocculation.
Sedimentation
It is the process where flocs settle down to the bottom. As the water and the flocs pass through the sedimentation basin, water moves slowly to settle down the flocs to the bottom. Flocs which collects to the bottom of the basin is called sludge.
Filtration
It is the process of removing contaminated particles from water. In this step, the water is passed through the filter to remove suspended floc from water. Filters are made up of a layer of sand and gravel or charcoal. Filters used for the removal of particles are slow sand filters, rapid sand filters and membrane filters. This removes even tiny particles present in the water.
Disinfection
It is the process of killing microbes in the water. In this step, disinfectant such as chlorine is added to the water before passing into the distribution system. It is added to kill if any microbes are present in the water. Residual amounts of disinfectants can be maintained to prevent the biological contamination of water in the distribution system.
Sludge drying
It is the process of removal of solids that are collected from the water by sedimentation process to drying lagoons.
Fluoridation
In this process, hexafluorosilicic acid is added to the water which decompose to yield fluoride ions. This fluoride level is adjusted to the optimum level to minimize the dental caries. Excess fluoridation leads to osteoporosis.
PH correction
PH of the drinking water should be 7. Lime is added to the fluoridated water to adjust the PH of the water. It stabilizes the natural soft water to prevent corrosion in distribution system.
Storage
Finally the treated water is stored in closed tanks or reservoirs from where it flows through pipes to homes.