How Stuff Works: Water Treatment Plant

Water treatment is a process of removing impurities from water in order to make it safe for consumption or for other purposes such as irrigation or industrial use. A water treatment plant is a facility that is designed to carry out these processes on a large scale. In this article, we will take a closer look at how a water treatment plant works.

Intake and Screening Process

Water from a natural source such as a lake or river is typically pumped into the water treatment plant. The intake process involves screening the water to remove large debris such as leaves, twigs, and other organic matter that could clog the plant's equipment. The water is typically passed through several screens of varying sizes to remove large particles that are greater than 0.2 inches in diameter.

Coagulation and Flocculation Process

After the water has been screened, it is then transferred to a mixing tank, where coagulants such as aluminum sulfate or ferric chloride are added to the water. The coagulants cause small suspended particles to clump together, making them easier to remove during the next stage of the process. This process is called coagulation.

Next, the water is passed through a series of mixing tanks where chemicals, called flocculants, are added to the water. These chemicals cause the clumped-up particles to form larger particles called flocs, which are easier to remove during the next stage of the process. This process is called flocculation.

Sedimentation Process

After the flocculation process, the water is transferred to a sedimentation tank. This is where the flocs that have formed in the previous stage settle to the bottom of the tank. This process is called sedimentation or clarification. The clear water at the top of the tank is then transferred to the next stage of the process.

Filtration Process

The water is then passed through a series of filters to remove any remaining suspended particles or impurities in the water that were not removed during the previous stages of the process. These filters can be made up of different materials such as sand or activated carbon. The filtered water is then transferred to a storage tank.

Disinfection Process

In the final stage, the water is disinfected to remove any harmful bacteria or viruses that may be present in the water. The most common method of disinfection is by adding chlorine to the water. Chlorine destroys harmful bacteria and viruses, making the water safe for consumption. The water is then tested to ensure that it meets the required level of purity before it is released into the distribution system.

Conclusion

Water treatment plants play a crucial role in ensuring that the water we drink is safe for consumption. The water treatment process involves several stages, each of which plays an important role in removing impurities from the water. By understanding how a water treatment plant works, we can appreciate the effort that goes into providing clean drinking water to millions of people every day.