water treatment plant: chapter 5 form 2

• Reservoir
• River water is pumped into a reservoir and kept for several days
• Sunlight treatment process involves several stages
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• Screening
• The water is pumped into the screening tank from the reservoir
• The metal screen removes large objects such as fish, twigs, branches and rubbish
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• Aeration
• Water is pumped upwards to dissolve the oxygen in air.
• This will also get rid of unpleasant smell and taste
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• Coagulation
• Water is then pumped into the coagulation tank
• slaked lime calcium hydroxide and ulum aluminium sulphate are added
• Alum coagulates suspended particles such as mud, soil and other particles to form larger solid lumps
• Slake lime calcium hydroxide reduces the acidity of the water
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• Mixing
• The water flows into the mixing tank
• this is to enable the chemicals added to be mixed properly
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• Sedimention
• The water then flows very slowly into the sendimentation tank.
• The coagulated particles sink to the bottom of the tank.
• Valves help to discard the coagulated particles at the bottom of the tank
• The cleaner water is allowed to flow to the filtration tank
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• Filtration
• In the filtration tank, sand and stone filters are used to remove the remaining suspended particles.
• The product is cleaner water which is free from solid impurities.
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• chlorination and fluoridation
• A small amount of chlorine is added to the water to kill some harmful microorganisms.
• Some flouride compound is also added to the water. Flouride helps to prevent dental decay.
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