Slides in this set
We need water in order to survive and so there's a huge demand for
it. We need to ensure that the water we use is clean, that its free
from poisonous salts (e.g. Phosphates and nitrates), and make sure
that it doesn't contain any harmful microbes.
Impurities in water can cause diseases such as cholera and dysentery.
A lot of our drinking water comes from reservoirs, and
water flows into reservoirs from rivers and groundwater.
Water companies will chose to build reservoirs in an area
with a good supply of clean water.…read more
The water that's collected in reservoirs goes to water treatment
works to be cleaned.
¬First the water is passed through a large mesh to remove big
clumps such as leaves and twigs
¬Its then mixed in with some chemicals in a sedimentation tank.
This causes the solids and microbes to clump together and fall to the
bottom of the tank.
¬The water is then filtered through gravel beds to remove all of the
solids. This is sometimes called the fine filter.
¬The water is then chlorinated to kill any harmful microbes that are
left inside of it
When this process is complete the water is safe enough to send to
Some people aren't satisfied with the process that water goes
through in water cleaning works and use other things to help ensure
that the cleanliness of their water is up to standard.
¬We can buy filters that contain carbon or silver to remove
substances from our tap water. The carbon removes the chlorine
taste of the water and the silver is there to kill bugs.
Some people that live in hard water areas buy water softeners that
contain ion exchange resins.
Hard water is water that contains magnesium and
calcium ions, and it doesn't easily form a lather with
We can make pure water through the process of distillation, which
involves boiling water to make a steam and then condensing the
This process can be expensive because it requires energy to boil the
water. Because of this we don't use this process to purify tap water,
because too much energy would be needed and tap water would end
up being too expensive.
Distilled water is used in some places though, like in chemistry labs,
because pure water is needed to make sure that things go right in
In some places fluorine is added to water because it helps to reduce
tooth decay. Some people are against this because its been proven
that high doses of fluorine can cause cancer and bone problems.
People are also concerned about whether its right to "mass
Some places add chlorine to their tap water to help prevent diseases.
Studies have shown that there's a link between adding chlorine to
water and an increase in cancer. Chlorine can react with other
substances in water to produce toxic by-products, which some
people believe can cause cancer.…read more