Water treatment

Seite 1

Composition of Water

Natural water supplies contain:

Solvents

Ions

Including sodium, calcium, magnesium, sulfate, hydrogencarbonate and chloride

Dissolved gases

Oxygen (needed aquatic organisms for respiration)

Carbon dioxide (Needed by plants for photosynthesis)

Microorganisms

Bacteria

Other forms of microscopic life

Can cause disease

Pollutants

Chemical fertilisers and pesticides

Washed through to rivers and lakes by rainfall

Seite 2

Abstracting water

Abstraction: Extracting water, either temporarily or permanently, for human use

Examples: Pumping underground water to the surface, building dams and reservoirs, taking waters from rivers and lakes, collecting rainwater, desalinating sea water

Desalination: Removing salt from sea water to convert it into water fit for drinking

There are often many objections to the building of dams and reservoirs because their construction requires:

The flooding of large areas of land

Destruction of habitats

Altering the appearance of the area

Seite 3

Treating water

Water sources include:

Rainfall collected in lakes or man-made reservoirs

Rivers

Underground water

See flashcards for defintions of each step

Seite 4

Fluoridation

Fluoride is often added to drinking water in order to prevent tooth decay

Fluoride in water has the following advantages:

Fluoride alters the structure of the enamel of young children so that it is more resistant to acid attack

Encourages remineralisation

Reduces ability of plaque bacteria to form acid

Some people object to fluoridation for the following reasons:

High levels of fluoride can cause dental fluorosis

Fluorine has been linked to bone disease and pain

Some people argue fluoridation may be unnecessary because most toothpastes contain fluorine

Some people believe drinking water should be as natural as possible

Some believe it is unethical to take away people's choice as to whether they consume fluorine in their water or not