Water pollution is defined as the contamination of water sources by substances that render the water unfit for drinking, cooking, cleaning, swimming, and other activities. Chemicals, trash, bacteria, and parasites are all examples of pollutants. All types of pollution eventually end up in the water. Water pollution is caused by one of four factors: sewage discharges, industrial activities, agricultural activities, and urban runoff, which includes stormwater. This article will explain to you Water Pollution which will be helpful in preparing the Environment Syllabus for the UPSC Civil Service exam.

Causes of Water Pollution

1. Sewage Water

• Sewage water includes discharges from homes and businesses.
• Human and animal excreta, food residues, cleaning agents, detergents, and other contaminants are found in sewage.
• Many pathogenic microorganisms can be found in household and hospital sewage.

2. Industrial Wastes

• Discharge of wastewater from industries such as petroleum, paper manufacturing, metal extraction and processing, chemical manufacturing, and others that frequently contain toxic substances.
• Particularly heavy metals (defined as elements with densities greater than 5 g/cm3 such as mercury, cadmium, copper, lead, and arsenic) and a variety of organic compounds.

3. Agricultural Factors

• Dissolved salts such as nitrates, phosphates, ammonia, and other nutrients, as well as toxic metal ions and organic compounds, are found in agricultural runoff.
• Fertilisers are rich in plant nutrients like nitrogen, phosphorus, and potassium.
• Excess fertilisers may leach into groundwater or be mixed with surface water.
• Pesticides include insecticides, fungicides, herbicides, and other chemicals.
• They contain a variety of chemicals, including chlorinated hydrocarbons (CHCs, such as DDT and Endosulfan), organophosphates, metallic salts, carbonates, and others.
• Many pesticides are non-biodegradable, and their residues last for a long time.
• Runoff carries waste from poultry farms, piggeries, and slaughterhouses into the water.

4. Dissolved Oxygen (DO)

• The presence of organic and inorganic wastes in water reduces its dissolved oxygen content.
• Water with a DO content less than 8.0 mg/L may be considered contaminated.
• Water with a DO content less than 4.0 mg/L is considered highly polluted.
• The DO content of water is critical for aquatic organism survival.
• Surface turbulence, photosynthetic activity, O2 consumption by organisms, and organic matter decomposition are all factors that influence the amount of DO in water.
• The higher the amount of waste, the faster it decomposes and consumes O2, lowering the DO content of water.

5. Biological Oxygen Demand (BOD)

• Organic waste water pollution is measured in terms of Biochemical Oxygen Demand (BOD).
• BOD is the amount of dissolved oxygen required by bacteria to decompose organic waste in water. It is measured in milligrammes per litre of water.
• A higher BOD value indicates that the water has a low DO content.
• BOD is not a reliable method of measuring water pollution because it is limited to biodegradable materials.

6. Chemical oxygen demand (COD)

• COD (chemical oxygen demand) is a slightly better method for measuring pollution load in water.
• COD measures the amount of oxygen required to oxidise organic (biodegradable and non-biodegradable) and oxidizable inorganic compounds in a water sample in parts per million.

7. Thermal and Radiation Pollution

• Thermal and nuclear power plants, as well as chemical and other industries, use a lot of water for cooling, and the used hot water is discharged into rivers, streams, or oceans.
• The discharge of hot water may raise the temperature of the receiving water by 10 to 15 degrees Celsius above the ambient temperature. This is called thermal pollution.
• The dissolved oxygen in water decreases as water temperature rises.
• Aquatic organisms, unlike terrestrial organisms, are adapted to a constant, uniform temperature in their environment. Temperature spikes kill fish and other aquatic animals.
• One of the most effective ways to reduce thermal pollution is to store hot water in cooling ponds and allow it to cool before releasing it into any receiving water body.
• Nuclear accidents near bodies of water or during natural disasters such as tsunamis and earthquakes pose the risk of radiation leakage (radiation exposure) into bodies of water. Eg: Fukushima Daiichi nuclear disaster.
• Mutations in the DNA of marine organisms are caused by radiation exposure. If the mutations are not repaired, the cell may develop into cancer.
• The thyroid gland absorbs radioactive iodine, which can lead to thyroid cancer.

8. Marine Pollution

• All natural and man-made pollutants eventually end up in the oceans.
• Coastal cities' sewerage and garbage are also dumped into the sea.
• Other sources of oceanic pollution include oil, grease, detergents, sewage, garbage, and radioactive waste discharged during navigation, offshore oil mining, and oil spills.

*For detailed notes of this topic, check this link Marine Pollution

9. Invasive Species

• Water hyacinth plants are the world's most troublesome aquatic weed, also known as the 'Terror of Bengal.'
• They proliferate in eutrophic water bodies, causing an imbalance in the ecosystem.
• They wreak havoc by causing stagnation of polluted water due to their rapid growth.

10. Underground Water Pollution

• In many parts of India, groundwater is being contaminated by seepage from industrial and municipal wastes and effluents, sewage channels, and agricultural runoff.
• Fluorides, uranium, heavy metals, and nutrients like nitrates and phosphates are common pollutants in many parts of India.
• Nitrates: Nitrate in excess in drinking water reacts with haemoglobin to form non-functional methemoglobin, impairing oxygen transport. Methemoglobinemia, also known as blue baby syndrome, is the name given to this condition.
• High nitrate levels can cause carcinogenesis and hasten eutrophication in surface waters.
• Metal traces: Lead, mercury, cadmium, copper, chromium, and nickel are all found. These metals have the potential to be toxic and carcinogenic.
• Arsenic: Arsenic in groundwater can be caused by seepage of industrial and mine discharges, as well as fly ash ponds from thermal power plants.
• Millions of people in India and Bangladesh (Ganges Delta) are exposed to groundwater contaminated with high levels of arsenic, a highly toxic and dangerous pollutant.
• Chronic arsenic exposure causes black foot disease. It can also cause diarrhoea, as well as lung and skin cancer.
• Fluoride: Fluoride in excess in drinking water causes neuromuscular disorders, gastrointestinal problems, tooth deformity, bone hardening, and stiff and painful joints (skeletal fluorosis).
• Knock-Knee syndrome is characterized by pain in bones and joints as well as outward bending of the legs from the knees.
• Fluorosis is a common problem in several states due to the consumption of high fluoride content water.

*For detailed notes on this topic, check this link Groundwater Pollution

Effects of Water Pollution

On Human Health

• Domestic and hospital sewage contain many pathogenic microorganisms, and dumping it into the water without proper treatment may result in an outbreak of serious diseases caused by water pollution, such as typhoid, cholera, and others.
• Metals in industrial wastewater such as lead, zinc, arsenic, copper, mercury, and cadmium are harmful to humans and other animals.
• Consumption of arsenic-polluted water causes arsenic accumulation in body parts such as blood, nails, and hair, resulting in skin lesions, rough skin, dry and thickening skin, and, eventually, skin cancer.
• Bacterial action converts mercury compounds in wastewater into extremely toxic methylmercury, which can cause numbness of the limbs, lips, and tongue, deafness, blurring of vision, and mental derangement.
• Mercury pollution of bodies of water causes Minamata (neurological syndrome) disease in humans.
• Lead poisoning is caused when lead interferes with a variety of body processes and is toxic to many organs and tissues.
• Lead compounds cause anaemia, headaches, muscle weakness, and a bluish line around the gums.
• Water contaminated with cadmium can cause itai itai disease, also known as ouch-ouch disease (a painful bone and joint disease), as well as lung and liver cancer.

*For detailed notes of this topic, check this link Effects of Water Pollution on human health

Economic Slowdown

• The United Nations estimates that by 2030, half of the world's population will be living in areas of high water stress.
• It is difficult to have a thriving economy when fresh water is in short supply for industrial, agricultural, and personal use.
• Lack of freshwater resources may limit the production of water-intensive goods such as automobiles, food, and clothing.

On the Environment

• Microorganisms involved in the biodegradation of organic matter in sewage waste consume a lot of oxygen and deplete the oxygen levels in the water, killing fish and other aquatic creatures.
• The presence of high levels of nutrients in water causes algal bloom (excessive growth of planktonic algae). Lakes age as a result of this.
• A few toxic substances, which are frequently found in industrial wastewater, can be biologically magnified (Biomagnified) in the aquatic food chain. For example, mercury and DDT.
• DDT at high concentrations disrupts calcium metabolism in birds, causing eggshell thinning and premature breaking, eventually leading to a decline in bird populations.

On Aquatic Ecosystem

• Polluted water reduces the amount of dissolved oxygen (DO), which kills sensitive organisms such as plankton, mollusks, and fish.
• A few tolerant species, such as Tubifex (annelid worm) and some insect larvae, may survive in highly polluted water with low DO levels. These species have been identified as indicator species for polluted water.
• Biocides, polychlorinated biphenyls (PCBs), and heavy metals kill sensitive aquatic organisms directly.

Eutrophication

• The lakes' nutrient enrichment promotes the growth of algae, aquatic plants, and various fauna. This is referred to as natural eutrophication.
• Human activities cause similar nutrient enrichment of lakes at an accelerated rate, and the resulting ageing phenomenon is known as cultural eutrophication.
• Lakes are classified as Oligotrophic (very low nutrients), Mesotrophic (moderate nutrients), or Eutrophic based on their nutrient content (highly nutrient-rich).
• Because of nutrients derived from their surroundings or organic wastes entering them, the vast majority of lakes in India are either eutrophic or mesotrophic.

Algal Bloom

• Phytoplankton (algae and blue-green bacteria) thrive on the excess nutrients and cover nearly the entire surface layer. This is referred to as an algal bloom.
• During the day, phytoplankton is photosynthetic, adding oxygen to the aquatic ecosystem. However, they consume far more oxygen at night due to their aggressive respiration.
• As the population of phytoplankton is very high, algal blooms accelerate the rate of oxygen depletion.
• Primary consumers, such as small fish, are killed as a result of oxygen deprivation caused by algal blooms.
• Algal blooms come in a variety of colours, but the most common are red or brown. These blooms are also known as red or brown tides.
• Coral reef destruction: This occurs as a result of a decrease in water transparency (increased turbidity).

Marine Pollution

• The discharge of chemicals into the ocean and its harmful effects are referred to as marine pollution.
• The potentially toxic chemicals adhere to tiny particles, which are then consumed by plankton and benthos animals, which are deposit or filter feeders that concentrate upward within food chains.
• Toxins can be found in consumed food items obtained from livestock and animal husbandry because animal feeds typically have a high fish meal or fish oil content.
• To reduce marine pollution and regulate individual states' use of the world's oceans, nations have come together to form two major conventions:
• Convention on the Dumping of Wastes at Sea (to be replaced by the 1996 Protocol)
• United Nations Convention on Law of the Sea (UNCLOS)

Water Crisis in India

• The difficulty in obtaining sources of freshwater for use due to depletion and deterioration of available water resources is referred to as a water crisis.
• Climate change may cause water shortages through altered weather patterns such as droughts or floods, increased pollution, and increased human demand and overuse of water.
• Furthermore, water scarcity in India is expected to worsen as the country's population grows to 1.6 billion by 2050.
• The NITI Aayog published the findings of a study warning that India is facing its "worst" water crisis in history, with demand for potable water exceeding supply by 2030 if action is not taken.
• According to a 2018 report by the British charity WaterAid, nearly 163 million of India's 1.3 billion people lack access to clean water close to home, the most of any country.
• Every year, nearly 600 million Indians face high to extreme water stress, and approximately 200,000 people die as a result of insufficient access to safe water.
• According to the study, twenty-one cities, including Delhi, Bengaluru, Chennai, and Hyderabad, will run out of groundwater by 2020, affecting 100 million people.
• If current trends continue, the country's Gross Domestic Product (GDP) will fall by 6% by 2050.

Control Measures of Water Pollution

• Before releasing sewage water and industrial effluents into bodies of water, they should be treated.
• Before hot water is released from power plants, it should be cooled.
• Domestic cleaning should be prohibited in tanks, streams, and rivers that supply drinking water.
• Excess fertiliser and pesticide use should be avoided.
• Organic farming and the effective use of animal waste as fertiliser should be encouraged.
• Water hyacinth (an aquatic weed) can purify water by removing some toxic materials and heavy metals.
• Oil spills in water can be cleaned using bregoli, a byproduct of the paper industry that resembles saw dust, an oil zapper, and microorganisms.
• Precipitation, the ion exchange process, reverse osmosis, and coagulation are some chemical methods that aid in the control of water pollution.
• Individually, reusing, reducing, and recycling wherever possible will go a long way toward mitigating the effects of water pollution.
• Implementation of the National Lake Conservation Plan (NLCP) and the National Wetland Conservation Programme (NWCP) for the conservation and management of identified lakes and wetlands in the country.
  • They were merged in February 2013 into an integrated scheme of the National Plan for Conservation of Aquatic Ecosystems (NPCA) to undertake various conservation activities such as waste water interception, diversion, and treatment, pollution abatement, lake beautification, and biodiverse management.

*For detailed notes of this topic, check this link Control Measures of Water Pollution

Conclusion

Water pollution is defined as the contamination of water sources with substances that make the water unsafe for drinking, cooking, cleaning, swimming, and other activities. Pollutants include chemicals, trash, bacteria, and parasites. Water pollution has spread beyond surface water to groundwater, the sea, and the ocean.

FAQs

Q1: What is water pollution?

Q2: What are the main sources of water pollution?

Q3: What are the effects of water pollution on human health?

Q4: How does water pollution impact aquatic ecosystems?

Q5: What measures can be taken to control water pollution?

MCQs

1. Which of the following is a common cause of water pollution?

a) Deforestation

b) Industrial effluents

c) Solar energy

d) Reforestation

2. What is the primary consequence of eutrophication in water bodies?

a) Increased fish populations

b) Decreased oxygen levels

c) Improved water clarity

d) Increased biodiversity

3. Which of the following pollutants is primarily responsible for the spread of waterborne diseases?

a) Heavy metals

b) Plastic waste

c) Pathogens

d) Pesticides

4. Which legislation is aimed at controlling water pollution in India?

a) Environment Protection Act

b) Water (Prevention and Control of Pollution) Act

c) Forest Conservation Act

d) Wildlife Protection Act

5. What role do wetlands play in controlling water pollution?

a) They increase water temperature

b) They serve as pollution sinks

c) They promote algal blooms

d) They increase sedimentation

GS Mains Questions and Model Answers

Q1: Discuss the causes and effects of water pollution in urban areas.

Answer: Water pollution in urban areas is primarily caused by industrial discharges, sewage, and stormwater runoff. Industries often release untreated or inadequately treated effluents containing heavy metals, chemicals, and organic matter into nearby water bodies. Domestic sewage contributes to nutrient overloads, promoting eutrophication and harmful algal blooms. Urbanization increases impermeable surfaces, leading to increased runoff that carries pollutants into waterways. The effects of water pollution are severe, impacting human health through waterborne diseases, reducing biodiversity, and harming aquatic life. Contaminated water sources can lead to gastrointestinal illnesses, respiratory problems, and even long-term chronic conditions. Additionally, polluted water bodies can affect local economies dependent on fishing and tourism. Addressing water pollution in urban areas requires comprehensive waste management strategies, stricter regulations on industrial discharges, and improved sewage treatment facilities to protect both human health and aquatic ecosystems.

Q2: Analyze the measures taken to combat water pollution and their effectiveness.

Answer: Measures to combat water pollution include the implementation of regulatory frameworks, public awareness campaigns, and technological advancements in wastewater treatment. Legislation like the Water (Prevention and Control of Pollution) Act has established standards for water quality and empowered authorities to take action against polluters. Furthermore, initiatives promoting the construction of sewage treatment plants (STPs) and the treatment of industrial effluents have shown positive results in urban areas. Public awareness campaigns have educated communities on the importance of reducing plastic usage and properly disposing of waste, which has led to community-driven clean-up efforts in local water bodies. However, challenges remain in enforcement, as many industries continue to flout regulations. Moreover, rapid urbanization often outpaces the development of adequate infrastructure. To enhance effectiveness, it is essential to integrate community participation in pollution control efforts, invest in green infrastructure, and adopt sustainable agricultural practices to minimize runoff. Ultimately, a multi-faceted approach that combines regulation, technology, and community engagement is crucial for effectively addressing water pollution.

Q3: Evaluate the impact of industrialization on water quality and aquatic ecosystems.

Answer: Industrialization significantly impacts water quality and aquatic ecosystems, primarily through the discharge of pollutants into water bodies. Factories release a variety of toxic substances, including heavy metals, chemicals, and organic waste, leading to contamination of local water sources. This pollution alters the physical and chemical properties of water, resulting in reduced dissolved oxygen levels and increased turbidity, which harm aquatic life. Species diversity suffers as sensitive organisms may be unable to survive in contaminated environments, leading to altered food webs and ecosystem imbalances. Additionally, industrial pollutants can bioaccumulate in aquatic organisms, posing health risks to humans who consume contaminated fish and shellfish. The socio-economic implications are profound, as communities reliant on fishing or tourism face declining livelihoods. To mitigate these impacts, stricter enforcement of environmental regulations, investment in cleaner technologies, and promoting corporate social responsibility in industries are essential. By prioritizing sustainable industrial practices, it is possible to protect water quality and preserve the integrity of aquatic ecosystems, ensuring long-term ecological and economic health.

Previous Year Questions on  Water Pollution

1. UPSC CSE Prelims 2021

Question: Which of the following is a consequence of water pollution?

a) Increased biodiversity

b) Improved water quality

c) Eutrophication

d) Decreased sedimentation

Answer: c) Eutrophication

Explanation: Eutrophication is a direct consequence of water pollution, resulting from nutrient overloads, leading to algal blooms and oxygen depletion in water bodies.

2. UPSC CSE Mains 2018

Question: Explain the effects of water pollution on human health and the environment. (200 words)

Answer: Water pollution has dire effects on both human health and the environment. Contaminated water sources can harbor pathogens, leading to diseases such as cholera, dysentery, and hepatitis. These waterborne diseases can disproportionately affect vulnerable populations, including children and the elderly, resulting in severe health crises. In addition to microbial threats, pollutants like heavy metals and chemicals can cause chronic illnesses, reproductive problems, and neurological disorders. Environmentally, water pollution disrupts aquatic ecosystems by reducing biodiversity, leading to the decline of species sensitive to pollution, such as certain fish and amphibians. It also contributes to eutrophication, resulting in oxygen depletion and the death of aquatic life. The socio-economic implications are significant, as fishing communities suffer due to dwindling fish stocks and increased health care costs associated with pollution-related illnesses. Protecting water quality through stricter regulations, effective waste management, and public awareness is essential to safeguard both human health and ecological integrity, ensuring sustainable use of water resources for future generations.