What is Water Pollution?
Water is a vital constituent for life support. The conservation and keeping up a good supply of water is thus very essential. The presence/addition of undesirable substances in water is referred to as water contamination. Natural, inorganic, chemical, radiological, and thermal contaminants impair the consistency of water, rendering it unsafe for drinking or usage. In this article, we have discussed the causes of water pollution and the types of water pollution.
Types of Sources of Water Pollution
The two types of sources of water pollution are:
Point Source
When pollutants are discharged from a specific location such as a drainpipe carrying industrial effluents discharged directly into a water body it represents point source pollution.
Non-point Source
Pollution discharged from diffused sources or over a wider area, such as runoff from farm fields, grazing lands, construction sites, abandoned mines, roads and highways, are examples of non-point sources.
What are the Causes of Water Pollution?
The causes of water pollution are:
Domestic wastes such as household detergents, sewage, etc.
Industrial wastes.
Offshore and oil drilling.
Thermal pollution
Nutrient pollution
Oxygen depletion
Microbiological pollution
Suspended matter
Chemical water pollution
Oil spillage
It is necessary to discuss the sources of water pollution while discussing what are the causes of water pollution. The main reasons for pollution of water are their sources.
Domestic Waste
The main sources of domestic waste are household detergents and sewage. It is generated from household activities like washing products, waste food and lots of other domestic items. The sewage, if not treated before being discharged, pollutes the water bodies.
Industrial Waste
Industries use water for many purposes such as processing, cooling and treatment of materials at various stages of production.
Nutrients Pollution
This is one of the main reasons of pollution in water bodies. Nutrient levels are high in some wastewater, fertilisers, and sewage. If they end up in bodies of water, they promote the growth of algae and weeds. When there are so many algae in the water, all of the oxygen is used up, and the species in the water die from lack of oxygen.
Surface water contamination applies to natural water found on the surface of the earth, such as rivers, lakes, lagoons, and the ocean. Surface water contamination applies to natural water found on the surface of the earth, such as rivers, lakes, lagoons, and the ocean. The reasons of pollution of surface water is Hazardous substances coming into contact with this surface water, dissolving or mixing physically with the water can be called surface water pollution. This is the major causes of water pollution.
Chemical Water Pollution
Many industries and farmers work with chemicals that end up in the water is called chemical water pollution. These include chemicals that are used to control weeds, insects, and pests. Metals and solvent from industries can pollute water bodies. These are poisonous to many forms of aquatic life and may slow their development, make them infertile and kill them.
Oxygen Depleting
Water bodies have microorganisms. When there is too much biodegradable matter (material that degrades quickly) in the water, it promotes microorganism activity, which consumes more oxygen. When oxygen is scarce, aerobic organisms perish, while anaerobic organisms prosper, creating dangerous toxins like ammonia and sulphides.
Pollutants of Water Pollution
Pollutants of water pollution are agents that cause water pollution. The major water pollutants are
Microorganism- bacteria and viruses are the main components.
Toxic organics- DDT, aldrin, endosulfan, chlordane, and malathion.
Heavy Metals- Arsenic, chromium, lead, copper, and iron.
Gross Pollutants
Oils, detergents, and shampoo.
Sediments.
Nutrients.
Oxygen demanding substances.
Treatment of Water Pollution
There are two types of wastes that are mainly responsible for water pollution:
Household waste includes mainly sewage and municipal garbage.
Industrial wastes include soluble matter. The proper disposal of these wastes can save the water from pollution to much extent.
Did You Know?
Oxygen is used up more quickly than it can dissolve in the water from the atmosphere. This drop may kill fish and other aquatic organisms.
Increased water temperature reduces the amount of light in the water available for plant growth.
Major water polluting industries in India include leather, pulp and paper industries.
FAQs on Causes of Water Pollution
1. What are five major causes of water pollution that are important for the CBSE 2025-26 board exams?
Five significant causes of water pollution frequently covered in the syllabus are:
- Domestic Sewage: Waste from households, including food waste, detergents, and human excreta, introduces organic matter and pathogens into water bodies.
- Industrial Effluents: Discharge from factories and industries often contains toxic chemicals, heavy metals (like lead and mercury), and thermal pollutants.
- Agricultural Runoff: Excess fertilisers and pesticides from farms are washed into rivers and lakes, leading to nutrient enrichment (eutrophication) and chemical contamination.
- Oil Spills: Accidental leakage of petroleum from ships and offshore drilling rigs can devastate marine ecosystems.
- Improper Waste Disposal: Dumping of solid wastes and plastics into water bodies directly pollutes the water and harms aquatic life.
2. Explain the difference between point and non-point sources of water pollution with examples.
This is an important distinction for understanding pollution control:
- Point Source Pollution refers to contaminants that enter a waterway from a single, identifiable source. Because the source is specific, it is easier to manage and regulate. An important example is a pipeline discharging industrial waste or sewage directly into a river.
- Non-point Source Pollution comes from diffuse, or scattered, sources. This type of pollution occurs when rainfall or snowmelt moves over and through the ground, picking up pollutants and depositing them into water bodies. Key examples include agricultural runoff from fields and urban runoff from roads and construction sites. It is much harder to control due to its widespread nature.
3. What is Biochemical Oxygen Demand (BOD), and why is it a critical parameter for evaluating water pollution?
Biochemical Oxygen Demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample. It is a critical parameter because it directly indicates the level of organic pollution. A high BOD value implies there is a large amount of biodegradable organic waste (like sewage). The decomposition of this waste consumes a significant amount of oxygen, leading to oxygen depletion in the water, which can kill fish and other aquatic life.
4. How does thermal pollution from industries and power plants negatively impact aquatic ecosystems?
Thermal pollution, the degradation of water quality by any process that changes ambient water temperature, has severe impacts. The primary effect is a reduction in the level of dissolved oxygen in the water, as warmer water holds less oxygen than cooler water. This creates a state of hypoxia. Additionally, the increased temperature can raise the metabolic rate of aquatic organisms, further increasing their demand for oxygen. This combination of lower oxygen supply and higher demand creates a stressful environment that can lead to fish kills and disrupt the entire aquatic food web.
5. Describe the process of eutrophication, a serious consequence of water pollution from agricultural and domestic sources.
Eutrophication is the process of nutrient enrichment of a water body, which leads to a dense growth of plant life, especially algae. Here is how it happens:
- Nutrient Loading: Excess nutrients, primarily nitrates and phosphates from fertilisers in agricultural runoff and detergents in domestic sewage, enter the water.
- Algal Bloom: These nutrients stimulate the rapid and excessive growth of algae, creating a thick layer on the water surface known as an algal bloom.
- Oxygen Depletion: When these algae die, they are decomposed by aerobic bacteria, a process that consumes vast amounts of dissolved oxygen.
- Aquatic Death: The severe depletion of oxygen suffocates fish and other aquatic animals, leading to the death of the ecosystem.
6. As per the CBSE 2025-26 syllabus, what are the important health effects on humans from heavy metal contamination in water?
Heavy metal contamination in drinking water poses serious health risks and is an important exam topic. Key effects include:
- Lead (Pb): Causes damage to the central nervous system, brain, and kidneys. In children, lead poisoning can lead to developmental delays and learning disabilities.
- Mercury (Hg): Can cause Minamata disease, which results in severe neurological damage, numbness in limbs, and impaired speech and vision.
- Arsenic (As): Long-term exposure can lead to skin lesions, cancer (skin, lung, and bladder), and cardiovascular diseases.
- Cadmium (Cd): Can cause Itai-itai disease, which damages bones and kidneys.
7. Suggest three effective methods that can be implemented to control water pollution.
To effectively control water pollution, a combination of technological and policy-based methods is crucial. Three important methods are:
- Wastewater Treatment: All domestic sewage and industrial effluents must be treated in Wastewater Treatment Plants (WWTPs) before being discharged into water bodies. This involves primary, secondary, and tertiary treatments to remove physical, biological, and chemical pollutants.
- Sustainable Agricultural Practices: Promoting the use of organic fertilisers and biopesticides, along with efficient irrigation techniques, can significantly reduce the amount of chemical runoff entering waterways.
- Stricter Enforcement of Laws: Governments must enforce stringent laws, such as the Water (Prevention and Control of Pollution) Act, 1974, to hold industries accountable and ensure they comply with effluent standards. Public awareness campaigns are also vital to encourage community participation in conservation efforts.
