4.7 Water pollution and its sources

Question 1

What are the sources of water pollution?

(3)

Answer 1

• domestic waste
• industrial processes
• agricultural practices

Question 2

Domestic waste

Answer 2

• sewage from rural and urban settlements (human waste) carry many pathogenic micro-organisms, increasing the content of nitrates and phosphates in rivers.
• Detergents, metals and other manufactured products contain traces of toxic chemicals.

Question 3

Industrial processes

Answer 3

• use of chemicals,
• the processing of metal ores,
• leaching of metals from waste heaps and dumps cause the presence of metals in rivers (e.g. manganese, mercury, copper).
• Gases from industrial chimneys enter the atmosphere, where they dissolve in water and form acid rain.

Question 4

Agriculture practices

Answer 4

• Surpluses of phosphorous and nitrogen not absorbed by the plants are washed from the land or percolate into the ground water. (lead to eutrophication)
• On farms, animal manure, synthetic fertiliser, and chemical pesticides are main sources.

Question 5

When does Water pollution occur

Answer 5

Water pollution occurs when harmful substances—often chemicals or microorganisms—contaminate a body ofwater, degrading water quality and making it toxic to humans or the environment