Figure 21.22: Wastewater Treatment: Most wastewater treatment facilities separate con-
taminants from water by passing wastewater through a series of settlement containers. At
each step, solids and particles are separated from water. Chemical and biological agents are
also used to remove any remaining impurities. ( 10 )
bacteria. Ideally, water treatment produces both liquids and solid materials that are not
harmful the natural environment.
Water can contain hundreds of contaminants. Not all treatment processes are able to remove
alloftheseparticlesandnotalltreatedwaterispureenoughtoqualifyassafedrinkingwater.
Sewage treatmentis any process that removes contaminants from sewage or wastewater.
Water purificationis any process used to produce drinking water for humans by removing
contaminants from untreated water. Purification processes remove bacteria, algae, viruses,
and fungi, unpleasant elements such as iron and sulphur, and man-made chemical pollutants.
The choice of treatment method used depends on the kind of wastewater being treated. Most
wastewater is treated using a series of steps, increasingly purifying the water at each step.
Treatment usually starts with separating solids from liquids. Water may then be filtered or
treated with chlorine. With each subsequent step, the water has fewer contaminants and the
effluent is increasingly pure.
Reducing Water Pollution
How can people reduce water pollution? And who is responsible for doing it?
People have two ways to reduce any kind of pollution: We can prevent people from polluting
water. And, we can use science to clean contaminants from water that is already polluted.
Governments can: