Water from rainfall or lakes is collected in a storage reservoir. Most of the suspended matter in the water settled to the bottom of the reservoir. Sunlight kills the harmful micro organisms in the water.
From the storage reservoir, water is pumped to the water works for treatment.
• first the untreated water is passed through large settling tanks where chemicals like potash alum are added to cause coagulation. The impurities clump together to form big particles of dirt which settle down rapidly.
• next , water is passed through a sand filter bed to remove the remaining fine particles of dirt.
• then, the water is treated with chemicals like chlorine to kill micro organisms. Useful chemicals like fluorine (prevents tooth decay) and iodine (prevents goitre) are also added here.
• finally the treated water is stored in a service reservoir or storage tank which is usually sited at the highest level than the town to which it supplies water.
• the purified water is distributed to the houses through a system of pipes.
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