Stages of water treatment

Water treatment refers to the process of removing all substances, whether physical, biological, or chemical, that can be harmful to the supply of water for domestic and human use. This treatment helps produce odorless, safe, clear, palatable, and colorless water. To help you know more, we will be talking about the different stages of water treatment.

Stages of water treatment

1. Screening 

Screening is one of the first stages of water treatment used to protect the main plant of water treatment units and helps them work efficiently. It is essential to use screens for removing large floating, suspended solids in the inflow. These materials make use of debris, leaves, rags, twigs, and paper to obstruct the flow through the damaged or plant equipment. 

Coarse screens have steel bars. They are corrosion-resistant and have their position five to fifteen cm apart. They exclude coarse materials such as fish and logs from getting inside the treatment plant. Screens are positioned at an angle of sixty degrees to remove collected material via mechanical raking.

Furthermore, fine screens work by keeping out the material responsible for blocking the pipework at the plant. They have steel bars five to twenty mm apart. A fine screen variation is a micro strainer that consists of one rotating drum made up of a stainless steel mesh with a small mesh size. Also, suspended matter like plankton and algae can get trapped. Shut-in solids get dislodged from the fabric with the help of high-water pressure jets. They use clean water and then get carried away for disposal. 

2. Coagulation

At the time of coagulation, workers in the plant treatment add some chemicals to the water which leads to the formation of particles on the water. Some of the common coagulants are –

These get included in the water at some point with a high amount of turbulence. The particles that these chemical forms are quite sticky and known as the floc. Floc also attracts some dirt particles that get very heavy and sinks beneath the tank storage in which it resides.

3. Sedimentation

Particles of dirt and floc sink in the bottom of the tank’s storage which we know as sediment. It is present in the water, along with the water flow into the basin of sedimentation at the time of the process. 

Besides, sedimentation tanks help to lower the velocity flow of the water to enable the suspended solids to settle. Also, the heavy particles of the floc settle at the bottom of your basin. They stay until it is removed. 

4. Filtration

Filtration refers to the procedure where the solids separate themselves from the liquid. In the water treatment, the solids that the sedimentation tank does not reduce get eradicated by passing them through gravel and sand beds to filter the water. With a current rate of four to eight cubic meters per square meter of the filter surface every hour, rapid gravity filters are often in use.

Moreover, the water that gets purified then passes through some layer of sand, gravel, and charcoal. The layer of gravel during the process is around one foot deep. Also, the layer of sand is two point five feet deep. 

Furthermore, pressure filters help maintain the hydraulic head, along with the gravity filters that work well in removing floc. Also, such filtration systems remove excess particles that are a part of the process of sedimentation, like algae and turbidity. Once done, the water will go to the closed tank.

While the filters have stuck solids, they go through backwashing. In the process, air and clean water are pumped upwards in the strainer. It helps to extricate the trapped contaminations. The water that carries the dirt pushes itself into the manure system. It can also be discharged into the river source after settling in the sedimentation tank to remove solids. 

5. Disinfection

After the water gets filtered, water treatment plants will add more chemical disinfectants like chlorine dioxide, chlorine, and chloramine to kill remaining viruses, parasites, and bacteria. To keep the water safe, water treatment plants must ensure that the water has low chemical disinfectant levels when it comes from the water treatment plants. The remaining disinfectant, therefore, kills germs that live in the pipes between the plant for water treatment and the tap.

Besides adding chlorine dioxide, chlorine, and chloramine, water treatment plants can disinfect water with UV or ultraviolet light and ozone. Ozone and UV light work well in disinfecting water. But such disinfection methods do not continue killing the germs when the water travels from the water treatment plant to the tap in your house.


There are several stages of water treatment that help in purifying the supply of water that leaves the water treatment plant and then goes to the drinking and domestic supply of water. For your convenience, we have discussed all the main stages of water treatment, including- 

The screening process uses fine and coarse screens to remove the trapped solids. Next comes the process of coagulation. In this process, the chemicals mix with the water. These chemicals are responsible for attracting dirt from the water. Some of the common chemicals that get used in this process are-

They, therefore, help eliminate most of the solid dirt from the water in the treatment plant.

The solid dirt and floc settle down at the bottom of the sedimentation tank. It happens during the sedimentation process by reducing the velocity of the flow of the water. Lastly, there are the processes of filtration and disinfection. Filtration helps in filtering out the floc and the dirt from the water. And finally, disinfection happens by adding chlorine and other similar substances to kill harmful parasites, viruses, and bacteria in the water. is the website where you can find the best water treatment systems for your home that will help you have clean drinking water.