Water treatment

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

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

Treating water

Water sources include: Rainfall collected in lakes or man-made reservoirs Rivers Underground water See flashcards for defintions of each step

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