WATER TREATMENT

screening

water passed through metal grills and meshes to remove large suspended objects (leaves, branches, litter)

sedimentation

water is held in tanks and smaller suspended particles are drawn to the floor of the tank by gravity, removing themselves from suspension.

aeration

air bubbles or sprays are used to introduce dissolved oxygen into the water helping destroy odours such as hydrogen sulphide and makes some metals less soluble in the water

flocculation/ coagulation/ clarification

chemicals are added to the water (eg. alum or other metal salts) to disrupt the electrostatic charges that hold tiny particles in suspension- the particles coagulate, get heavier and sink to bottom

filtration

water is passed through a series of very fine filters, some of which are fine enougj to remove bacteria from the water

activated carbon filter

used to remove organic chemicals like pesticides from the water- the chemicals absorb into the carbon filter

sterilisation

removing pathogens from water- adding chlorine, ozone, exposure of the water to UV light

fluoridation

addition of fluorine to improve strength of human teeth, reducing tooth decay