What you'll learn
What pollutes water and how to keep it clean.
Causes
- Sewage and organic waste, fertilisers and pesticides (agricultural run-off), industrial chemicals, oil spills and plastics.
Effects
- Eutrophication: excess nutrients cause algal blooms, which block light and, on decay, remove oxygen — killing fish and other life.
- Spread of water-borne diseases (e.g. cholera) where sewage contaminates drinking water.
Management
- Sewage treatment, controlling fertiliser use, legislation, and clean-up of spills.
- Providing safe drinking water and sanitation.
Exam tips
- Explain the sequence of eutrophication step by step.
- Link pollution sources to specific effects.
Common mistakes
- Describing eutrophication without the oxygen-depletion step.
- Confusing water pollution with water scarcity.