[Science Form 2] Different Stages For Water Treatment

1. Filtration
   
   • Here, the remaining substances and sediment pass through layers of sand filters and are removed.
     
     
2. Disinfection
   
   • In this tank, a small quantity of chlorine is added to the water to kill any remaining bacteria. A small amount of fluoride is also added to the water to help prevent tooth decay.
     
     
3. Coagulation
   
   • From the reservoir, water is pumped into this tank and mixed with slaked lime and alum. Alum makes the fine solid particles stick together and form larger solid lumps, and slaked lime reduces the acidity of the water.
     
     
4. Reservoirs
   
   • River water is pumped here and left for several days. During that time, sunlight kills most of the dangerous bacteria in the water. Mud, silt and other suspended substances will sink to the bottom and a metal screen removes large solid particles from the water.
     
     
5. Storage
   
   • Water that has been treated enters these tanks before being pumped into the supply ponds, which are usually found on hilltops or at higher levels. From the supply ponds, water flows through pipes to houses.
     
     
6. Sedimentation
   
   • The water then flows very slowly into these tanks, where the larger lumps sink to the bottom of the tank and are then removed.