The purification of Water

• Large residential areas such as Harare, Chitungwiza and other urban establishments are supplied with piped running water
• This water is treated so that it is safe to drink and for other domestic use

Water purification process

• The water is usually obtained from a dam, reservoir, lake or river
• It is then passed through a purification plant before it is piped for domestic and industrial use
• The purification plant uses chemical and physical process to make sure the water is safe and clean
• First the water is allowed to settle so as to remove solid particles which fall to the bottom
• The solid matter is then removed
• A chemical called a flocculant is usually added to speed up this sedimentation process
• The water is then filtered through sand to remove any remaining solid particles
• The water will now be clean but not yet safe to drink
• The water is then chlorinated 
• Chlorine is added to kill any pathogens, bacteria and any other undesirable micro-organisms
• At this stage the water is then safe to drink
• It is then passed into a storage reservoir until it is pumped to houses
• The water is constantly tested  for bacteria at various stages to make sure it is safe to drink

Domestic filters

Home built filter

• Domestic filters are used in some homes to make water safe to drink when it is obtained from an unsafe source such as a river
• They make use of sand particles of different sizes
• With time the sand becomes compacted and microorganisms grow within the filter helping to make it more effective
• The sand in this domestic  filters has to be replaced from time to time

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