Quick Summary
- Water pollution happens when harmful materials contaminate rivers, lakes, oceans, and underground water
- Main sources include factories, farms, sewage systems, oil spills, and improper waste disposal
- Polluted water spreads diseases like cholera and typhoid fever common in Nigeria
- Effects include death of fish, unsafe drinking water, and damage to the environment
- Prevention requires proper waste treatment, laws, and public awareness
What is Water Pollution?
Water pollution occurs when harmful substances enter water bodies and change the water quality. Clean water is essential for life, but when pollutants mix with it, the water becomes dangerous. In Nigeria, many people suffer from diseases caused by polluted water because some communities lack clean water supply.
The Niger Delta region faces serious water pollution from oil spills. Lagos lagoon receives waste from millions of people daily. Rivers in industrial areas like Ikeja and Aba often carry factory waste. These are real examples of water pollution affecting Nigerians.
Major Water Pollutants
1. Sewage and Domestic Waste
Sewage contains human waste, soap, and dirty water from homes. Many Nigerian cities dump untreated sewage into rivers and lagoons. This waste carries harmful bacteria and viruses that cause diseases. In Lagos, open drains often overflow during rain and pollute nearby water bodies.
2. Industrial Waste
Factories release chemicals, heavy metals, and hot water into rivers. Textile factories in Kano, breweries in Lagos, and pharmaceutical companies across Nigeria produce liquid waste. If this waste is not treated before release, it poisons the water. Heavy metals like mercury and lead can stay in water for years.
3. Agricultural Waste
Farmers use fertilizers and pesticides to grow crops. Rain washes these chemicals from farms into rivers and streams. The chemicals include nitrogen compounds and phosphates. Too much of these nutrients causes algae to grow fast, covering the water surface. This blocks sunlight and kills fish and plants below.
4. Crude Oil Spills
Nigeria faces frequent oil spills in the Niger Delta. When pipelines break or tankers leak, crude oil spreads over water surfaces. Oil forms a thick layer that stops oxygen from entering the water. Fish and other water animals die. The oil also damages fishing nets and boats, destroying the livelihood of fishing communities.
5. Plastic and Solid Waste
Plastic bottles, bags, and containers thrown into gutters end up in rivers and oceans. Unlike organic waste, plastic does not decay. It breaks into tiny pieces that fish eat, mistaking them for food. Lagos generates thousands of tons of plastic waste daily, much of it ending up in the lagoon and Atlantic Ocean.
6. Radioactive Substances
Though rare in Nigeria, radioactive materials from medical facilities or research centers can pollute water. These substances are extremely dangerous even in small amounts. They cause cancer and genetic damage.
Sources of Water Pollution
| Source Type | Examples | Main Pollutants |
|---|---|---|
| Point Sources | Factory outlets, sewage pipes, oil tanker leaks | Chemicals, heavy metals, oil, untreated sewage |
| Non-Point Sources | Farm runoff, street litter, atmospheric deposition | Fertilizers, pesticides, plastic, dirt, chemicals in rain |
| Urban Sources | Markets, motor parks, residential areas | Garbage, sewage, motor oil, detergents |
| Mining Activities | Illegal mining in Zamfara, tin mining in Jos | Heavy metals, sediments, acid mine drainage |
Effects of Water Pollution
Health Effects on Humans
Drinking or using polluted water causes many diseases. Cholera outbreaks in Nigeria often trace back to contaminated water. Typhoid fever spreads through water containing sewage. Guinea worm disease, though almost eliminated, came from drinking water with tiny infected organisms. Skin diseases develop when people bathe in polluted water.
Children are most affected because their bodies are still developing. Diarrhea from bad water kills many infants in rural areas. Lead in water damages the brain, especially in children.
Damage to Aquatic Life
Fish need oxygen dissolved in water to breathe. Pollutants reduce oxygen levels, suffocating fish. Oil spills coat fish gills, preventing them from absorbing oxygen. Chemicals poison fish and shellfish. When fish die, fishermen lose income. Communities that depend on fishing for food and money suffer greatly.
Environmental Damage
Pollution destroys mangrove forests along the coast. These forests protect the land from erosion and serve as breeding grounds for fish. Birds that eat poisoned fish also get sick or die. The entire ecosystem suffers when water is polluted.
Economic Losses
Nigeria spends billions of naira treating water-related diseases. Tourism suffers when beaches are dirty with oil or plastic. Property values fall in areas near polluted water. The fishing industry loses money when fish populations decline.
How Water Pollution Spreads
Pollutants move through water in several ways. Rivers carry waste downstream, affecting communities far from the pollution source. Underground water gets polluted when chemicals seep through soil. Ocean currents spread oil spills across large areas. Even rain can carry air pollutants down into lakes and rivers.
Once water is polluted, cleaning it becomes very difficult and expensive. Prevention is always better than trying to fix the problem later.
Common Exam Mistakes
Students often make these errors in WAEC/NECO exams:
- Confusing water pollution with air pollution: Be specific about water-based pollutants, not smoke or gases
- Listing sources without explaining: When asked to “explain,” describe how each source causes pollution, not just naming them
- Mixing up effects and causes: Cholera is an effect, not a cause of water pollution; sewage is a cause
- Forgetting to mention specific pollutants: Say “mercury and lead” instead of just “chemicals”
- Poor organization: Group similar points together rather than random listing
Practice Questions
Multiple Choice Questions
1. Which of the following is NOT a water pollutant?
a) Sewage
b) Crude oil
c) Nitrogen gas in air
d) Agricultural fertilizers
Answer: c) ✓ Nitrogen gas in air (nitrogen becomes a water pollutant only when washed from fertilizers into water)
2. The most common disease spread by polluted water in Nigeria is:
a) Malaria
b) Cholera
c) HIV
d) Tuberculosis
Answer: b) ✓ Cholera
3. Which Nigerian region suffers most from oil spill water pollution?
a) Niger Delta
b) Jos Plateau
c) Sahel Region
d) Middle Belt
Answer: a) ✓ Niger Delta
4. When fertilizer runoff causes excessive algae growth in water, this process is called:
a) Acidification
b) Salinization
c) Eutrophication
d) Sedimentation
Answer: c) ✓ Eutrophication
Essay Questions
1. (a) Define water pollution. (2 marks)
(b) State four sources of water pollution in Nigeria. (4 marks)
(c) Explain three effects of water pollution on human health. (6 marks)
Examiner’s Tip: For part (c), don’t just list diseases. Explain how the pollutant causes the disease. Example: “Sewage in water contains bacteria like Vibrio cholerae which causes cholera when people drink the contaminated water. Cholera leads to severe diarrhea and dehydration.”
2. Describe five types of pollutants commonly found in Nigerian water bodies and explain how each enters the water. (10 marks)
Examiner’s Tip: For 10 marks, you need both the pollutant name AND how it enters water. Structure each point as: “Crude oil enters water bodies through pipeline leaks and oil tanker spills, especially in the Niger Delta where oil exploration is intensive.”
3. (a) Distinguish between point source and non-point source water pollution. (4 marks)
(b) Give three examples of each with reference to Nigerian situations. (6 marks)
Examiner’s Tip: “Distinguish” means show clear differences. Point source = can identify exact location (factory pipe). Non-point source = spread over large area (farm runoff across many fields).
Memory Aids
Remember major water pollutants with “SOAP”:
- Sewage (human waste)
- Oil spills (petroleum products)
- Agricultural waste (fertilizers, pesticides)
- Plastic and solid waste
Effects on humans – “DISC”:
- Diseases (cholera, typhoid)
- Infant mortality (diarrhea in babies)
- Skin problems (rashes, infections)
- Chemical poisoning (lead, mercury)
Related Topics
- Effects of Water Pollution – detailed health and environmental impacts
- Control of Water Pollution – methods to prevent and reduce pollution
- Treatment of Water for Town Use – how water is purified
- Types of Pollution – comparison with air and land pollution
- Water Definition – importance of clean water for life