The water treatment process

Summary

This video explains the intricate process of water treatment, from the collection and storage of water in reservoirs to its filtration, coagulation, and disinfection. The water undergoes various stages, including the removal of large particles, the formation of floc for sedimentation, and fine filtration through sand or carbon. Ozone gas and chlorine are used for further purification and disinfection. Finally, the water is adjusted for pH levels before being distributed through an extensive pipe network, ensuring that clean, safe drinking water is delivered to homes.

Takeaways

• 😀 Water is essential for customers, but rainfall is seasonal and unpredictable, which is why reservoirs are used for storage to ensure a consistent water supply.
• 😀 The initial step in water treatment involves passing water through mesh screens to remove large foreign objects like sticks, weeds, and debris.
• 😀 Air is introduced into the water to eliminate odors, gases, and allow dissolved metal salts to separate and be filtered out.
• 😀 Coagulants, such as ferric or aluminium sulfate, are added to the water to bind suspended particles, forming 'floc' that can be removed.
• 😀 The flocculation process requires quick and thorough mixing of water and coagulants in a device called a flash mixer.
• 😀 The clarification process separates the flock from the water, creating a sludge blanket that is periodically drained and removed.
• 😀 Fine particles are removed by rapid gravity filtration (RGF), where water is filtered through sand or other fine materials.
• 😀 Ozone gas injection and granular activated carbon (GAC) are sometimes used to further treat river water by removing organic materials.
• 😀 The water is disinfected with chlorine to eliminate any remaining harmful bacteria, ensuring safe drinking water.
• 😀 Chlorine remains in contact with water for a set period to effectively disinfect it before it is distributed to homes.
• 😀 pH levels are adjusted during the treatment process to ensure the water is neither too acidic nor alkaline, preventing damage to pipes and fittings.
• 😀 Once treated, the water is distributed through a vast mains pipe network, reaching homes to provide clean, safe drinking water.

Q & A

Why is water treatment necessary despite water being available from rainfall?

Water treatment is necessary because rainfall is seasonal and increasingly unpredictable. To ensure a continuous supply, storage reservoirs are used to store water for treatment during dry periods.

What is the purpose of the initial mesh screening in the water treatment process?

The initial mesh screening helps to remove large debris such as sticks, water weeds, and other foreign objects from the water before further treatment.

How does aeration contribute to water treatment?

Aeration involves adding air to the water to remove odors and gases. It also helps certain dissolved metal salts to separate, which is beneficial for the subsequent treatment stages.

What is flocculation, and how does it occur during water treatment?

Flocculation is the process where a coagulant (such as ferric or aluminium sulfate) is added to the water. The coagulant causes suspended particles in the water to stick together, forming clumps called floc, making them easier to remove.

What role does the flash mixer play in the coagulation process?

The flash mixer is a special device used to quickly and thoroughly mix water with the coagulant. This rapid mixing ensures that the coagulant reacts effectively with the water, enabling the formation of floc.

What is the purpose of the clarification stage in water treatment?

During clarification, the floc formed in the previous stage settles into sludge, which is separated in a specially designed tank called a clarifier. The sludge is periodically drained and removed for safe disposal.

How is filtration performed in the water treatment process?

Filtration is carried out by passing water through very fine sand or sand-like material to remove any remaining particles. This step ensures that the water is further purified after the clarification stage.

What is the role of granular activated carbon (GAC) in water treatment?

Granular activated carbon (GAC) is used to filter the water and remove undesirable organic materials. It helps in purifying the water, especially when dealing with river water, and is often combined with ozone gas injection for additional treatment.

Why is chlorine added to the water during treatment?

Chlorine is added to disinfect the water, ensuring that harmful bacteria are killed. It is the most effective method for disinfection and is used globally to provide safe drinking water.

How is the pH of the water adjusted during treatment, and why is this important?

The pH of the water is adjusted to make sure it is neither too acidic nor too alkaline. This is important for preventing corrosion in pipes and ensuring that the water is safe for consumption.