WHAT HAPPENS TO DRINKING WATER?
Before water gets to our homes it undergoes a series of processes to remove impurities and make it healthy to
drink. In Sydney, water filtration plants treat water from dams and rivers, and one desalination plant extracts
fresh water from seawater.
Seawater
Fresh water
Ocean water flows slowly through large pipes
then is pumped to be filtered. Fish can easily
swim away from the inlet structures.
Engineers select from the clearest, cleanest water layers
in the dam. The best layers change with temperature and
rainfall. Water is pumped to be filtered.
Screens prevent plants and other solid materials from entering
water pipes.
Change the water acidity
Lime (calcium hydroxide) or other chemicals are used to change
the acidity of the water. This makes it easier to remove small
particles and microorganisms.
Attract and remove particles
Ferric chloride and polymers attract small particles and
microorganisms. They form into larger clumps that are easy to
remove with filters. This process is called coagulation.
Reverse osmosis in the
desalination plant
pressure
semipermiable
membrane
Filter impurities
Water passes through a filter layer about 1.5 metres thick,
made of crushed coal and sand. Impurities are trapped within
the filter bed. The filter is regularly cleaned with air bubbles
and water pumped backwards through the filter bed. Impurities
from fresh water are collected and used as fertiliser (biosolids)
in landscaping and agriculture.
Add minerals and chemicals for health
Chlorine is added to kill remaining bacteria and any other
microorganisms that might enter through cracked pipes.
Fluoride is added for dental health. The NSW government
made this mandatory in 1957. Lime and carbon dioxide are
sometimes added to adjust the acidity of the water.
salt
water
fresh
water
Transport and store
Water is pumped straight into the pipe network or to a reservoir
where it is held until needed in your home.