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Chemistry revision Topic 2: Water Treatment (Water Purification (1…
Chemistry revision Topic 2: Water Treatment
Potable
: Drinkable
Sources of water:
Surface water:
Lakes, rivers and reservoirs
Runs dry during summer
England and Wales
Waste water:
Contaminated by human process (industrial processes)
Treating waste water better for environment compared to disposing as waste water contains pullutants
How easy waste water is to treat depends on the levels of contaminants in it
Ground water:
Aquifers (rocks that trap water underground)
South-east England where surface water is limited
70% domestic water supply comes from ground water
Water Purification
All water has to go through a basic process to make it potable.
Aquifers need less treatment as quite clean
1.Filteration
Wire mesh stops large objects (e.g. large twigs) and gravel and sand beds filter out any solid bits
2.Sedimentation
Iron sulphate or aluminium sulphate added to water to make fine particles clump together and settle at the bottom
3.Chlorination
Chlorine gas is bubbled through to kill harmful bacteria and other microbes
Distilling sea water
Where there isn't enough surface water or ground water, sea water is distilled to provide potable water
Sea water is boiled to produce steam which is condensed to separate water from dissolved salts
Needs lots of energy, so really expensive
Deionised water:
For experiments that involve mixing or dissolving something in water, use deionised water
Has ions (calcium, iron and copper) that is in normal tap water, removed
Ions harmless in tap water but can interfere with reactions.
Using normal water could give your experiment a false result