How Is Water Purified in a Water Treatment Plant?

Written by AOS Treatment Solutions on July 23, 2018
how is water purified in a water treatment plant?


Water treatment plants are critical for a municipality so that clean water can be supplied to the local community. The process of water purification in water plants requires specialists to ensure safe and effective operation.

The whole procedure occurs in stages and involves a combination of technical processes.

How Is Water Filtered in Water Purification Plants?

How do municipalities clean water so that the community and environment remains healthy? There are several water purification steps involved in the primary and secondary wastewater treatment process. Here’s how water purification plants process water once it has been collected.


When water enters a treatment plant, the first stage in the process is coagulation where chemicals are added to the water supply to enable microparticles and small solids to stick together. Polyelectrolyte, ferrous sulfate, and aluminum sulfate are examples of chemicals used in the water treatment plant process to aid coagulation.

Adding these coagulating agents during these water treatment plant steps requires careful administration by qualified engineers, as measurements of the chemicals need to be precise. Quality standards also need to be met as part of the regulatory processes within water treatment plants. This includes regular maintenance of the system by qualified engineers.

how do water treatment plants purify water?


Once water has been treated with the coagulation chemicals it enters a tank with giant paddles. These mix the chemicals and water together and enable the micro particles to form into larger pieces that are likely to stick together, making the sedimentation process in water treatment more effective. This process is known as flocculation.


Once the flocculation process is complete the water enters the sedimentation phase. Once the water is in the primary settling basins the large particles formed during the coagulation and flocculation stage separate and settle. This leaves cleaner water for further processing in the treatment plant. The solids form a sludge layer which forms on the bottom of the tank and is later removed via sludge thickening and reused on the land.


Once clarified water leaves the sedimentation basins in the treatment plant, chlorine is added during the disinfection water treatment stage. After the chlorine wastewater treatment occurs, ammonia follows which forms chloramine. This chloramine disinfected water passes through a further set of basins to complete the disinfection process.

pH Adjustment

process of water purification system in water works

After the disinfection phase the water undergoes a pH treatment stage. Lime or calcium oxide makes water less acidic by adjusting the pH. It is also less corrosive to domestic water pipes. Polyphosphate solution is also added to the water at this stage to keep the lime dissolved.


Once water exits the sedimentation basins, fluorosilicic acid is added in small quantities. This helps fluoridate the water supply to help in the prevention of dental decay.


Finally, water goes through a filtration process using rapid gravity filters. Sand is commonly used in this type of filter and it removes any further sediment or particles in the water. During this final stage water is passed through a filter in a regulated manner. Any particles stick to the filter, leaving clean water to be piped into the municipal supply. Pumping stations pump water to domestic customers using pipelines.

Final Thoughts on The Process of Water Purification in Water Plants

The water purification plant processes are critical to maintaining a safe supply of water for public and commercial use. It is vital that the processes are quality-checked regularly to ensure that standards are being met and the public gets clean, healthy water. This means using specialists with the expertise to maintain treatment plants and who know how water is purified.

Make sure your treatment plant has scheduled maintenance visits and quality checks from municipal water treatment experts, like those at AOS, so you continue to provide an excellent service to the public.

Contact AOS today with questions about our products and services!


Posted Under: Wastewater Treatment Solutions