Water must be free of poisonous salts (phosphates and nitrates) and harmful
microbes. Microbes can cause diseases such as chlolera
Water from reservoirs goes to the water treatment works for treatment.
The water passes through a mesh screen to remove big bits like twigs.
Chemicals are added to make solids and microbes stick together and fall to the bottom/
The water is filtered through gravel beds to remove all the solids
Water is chlorinated to kill off any harmful microbes left
Some people buy carbon or silver filters to remove substances from their tap
water. Carbon filters remove the chlorine taste and silver is supposed to kill
bugs.
Totally pure water can be produced by distillation- boiling water to make steam adn condensing the
steam. This is expensive.
Fluorine is added to drinking water in some parts to reduce tooth decay. Chlorine is added
to prevent disease. However some studies show this can increase certain cancers. Fluorine
can also cause cancer and bone problems in high doses.
Levels of chemicals added to drinking water need
to carefully monitored.