Introduction

Water treatment plants play a crucial role in maintaining public health by removing contaminants from the water supply. One of the key steps in the treatment process is filtration. In this article, we will explore how water is filtered at a treatment plant.

Sedimentation

The first step in the filtration process is sedimentation. The water is allowed to settle in a tank, and the heavier particles – such as sand and silt – sink to the bottom. This process is aided by the addition of chemicals such as alum, which causes the particles to clump together and settle more easily. The water is then drained off the top of the tank and transferred to the filtration stage.

Coagulation and Flocculation

The next stage of the filtration process is coagulation and flocculation. In this stage, chemicals are added to the water to help the remaining particles stick together and form larger clumps. This makes it easier for them to be removed in the filtration stage. Chemicals commonly used for this purpose include aluminum sulfate, ferric chloride, and polymers.

Filtration

In the filtration stage, the water is passed through a series of filters to remove any remaining particles. The most common types of filters used are sand filters, activated carbon filters, and membrane filters. Sand filters are made of layers of sand and gravel, which trap particles as the water passes through. Activated carbon filters use activated charcoal to absorb impurities, and membrane filters use a semi-permeable membrane to remove particles.

Disinfection

After filtration, the water is disinfected to kill any remaining bacteria and viruses. The most commonly used disinfectant is chlorine, although other chemicals such as ozone and ultraviolet (UV) light can also be used. Chlorine is added to the water in precise amounts to ensure that all harmful microorganisms are destroyed, but that the residual concentration is safe for consumption.

Conclusion

Overall, water filtration is a critical step in the treatment process that helps ensure that the water supply is safe to drink. Understanding the various stages in the filtration process can help us appreciate the importance of this aspect of water treatment, and the efforts that are made to keep our water supply clean and healthy.