Key Sources, Harmful Effects, and How We Can Prevent Water Pollution
Two-thirds of our planet is made up of water which is as big as 1 octillion litre. 70 percent of the human body is made up of water. It is a universal solvent. It is the only substance that exists in all 3 forms of matter on this planet. Today, united nations have recognised water as a basic human right, besides considering it as an economic commodity.
‘Pure’ water form is thought to be water with the minimum amount of gases, minerals and life. But for all practical purposes, it is generally thought to have the least amount of solutes. High-quality water is essential for drinking purposes, but for any other needs, water quality can be flexible.
What is Water Pollution?
Pollution is the introduction of contamination into the environment. Water pollution is the presence of extreme levels of pollutants (hazards) in a water body, such that it is no longer suitable for regular human usage such as bathing, cooking or drinking.
Polluting water is commonly seen with the involvement of human activities such as throwing waste, industrial and agricultural effluents, chemical discharge, etc. This leads to the degradation of water quality and affecting aquatic life. When humans or animals consume this water for thirst, the health effects caused are adverse to life. Only less than 0.3% of the earth’s water is suitable for normal drinking.
Sources of Water Pollution
There are many sources of water pollution. Most of the freshwater is surface water. Oceans, lakes, rivers, streams, ponds and other water bodies can become sources of pollution. Another important source of freshwater is underground water. It can also get contaminated by seepage of harmful chemicals from the surface.
There are two major sources when seen from the origin of the contamination. One is the ‘point’ source pollution, which means that the source of the pollution originates from a specific place. The other is ‘nonpoint’ source pollution as contamination from diffuse options. Transboundary contamination means it will not be limited to a country but can affect other places as well. Other common causatives for water pollution include Urbanization, high use of Detergents, insecticides and fertilizers, Deforestation. Even many social and religious ceremonies are key sources of water pollution.
Let us Look at a Few Other Modern Sources of Water Contamination with Examples.
Water Pollution – A Modern Epidemic
Most causes of water pollution originate from human activities and their waste products. The sources of water pollution are numerous, but some of the major pollutants in today’s modern scenario are as follows :
Industrial Waste: Many regular industrial activities release enormous amounts of toxic chemicals such as lead and mercury. They spread to other living species when humans use this contaminated product for regular purposes. It also affects the biodiversity of the water body.
Sewage and Waste: Tonnes of sewage waste is dumped into water bodies. This not only causes pollution but also releases dangerous disease-causing pathogens.
Mining: Mining in today’s generation is key to the major lake and river pollution. This process brings out harmful chemicals that are buried deep under the earth’s surface. When this comes in contact with water, the effects are dangerous to any living creature.
Marine Dumping: The garbage generated every day is dumped into the seas and oceans going as far as to give rise to garbage islands. An easy step of throwing waste products only in the bin can reduce more than half of the water pollution levels.
Agricultural Activities: The use of chemical fertilisers, pesticides and other runoffs during irrigation flows into the water bodies. These chemicals cause pollution to water bodies in a short span of time.
Radioactive Wastes: After usage of radioactive materials for nuclear wagons or as an energy source, they are mostly dumped into water bodies or in glaciers that will immediately mix with water when the temperature rises.
Urbanisation and Population growth: Cities are unable to meet the water demand of its growing population. This has caused contamination and loss of water due to overuse.
Effects of Water Pollution
The most diverse effects of water pollution on humans is when it affects the health of people. Disruption of aquatic life is the primary effect of water pollution. Polluted water contains many disease-causing elements such as bacteria and viruses which trigger other harmful diseases, namely cholera, giardia, and typhoid. It can even lead to chronic conditions, including hormonal imbalances, hepatitis, altered brain function to cancer. A pregnant woman is especially prone to these water-borne diseases. Also, swimming in polluted water is a high risk as it can cause skin and eye allergies.
The environment is also disturbed as it slowly kills animals and plant life that are dependent on them for nourishment. It also supports the growth of harmful organisms that destroy the biodiversity of the water body. Certain algae growth reduces the level of oxygen in the water, killing everything in it. In some areas, pollution is so severe that it causes “dead zones” where there is no life.
Minamata Incident
The 1932’s Minamata Incident is the worst record case in the history of water pollution. Methylmercury and its effluents started to flow from a factory in Japan. Methylmercury is one of the key sources of causing neurological disorders in human beings. The effects were initially not observable until seashell started to grasp these toxic chemicals into them. People and other local men started to consume these fishes, and the ill-effects were soon prominent.
Animals such as cats and dogs were the first ones to suffer the ill-effects of this chemical. The term ‘dancing cat disease’ was coined from this incident, referring to the sounds of cats before they convulse and die. The symptoms were worse, including loss of motor coordination, acute mercury poisoning, ataxia, and even damage to speech and hearing. Severely affected persons recorded to have coma and paralysis, leading to demise.
The Japanese government and officials took 36 years to understand the seriousness of the incident and provided support funds to the victims. Soon the Japanese government also opened avenues to start protecting their water bodies and took proper measures for the prevention of water pollution.
Pollution of the Ganges
The 6th most polluted river in the world is India’s Ganges (Ganga). Cremating dead bodies of humans along with other religious practises, quickly developed water contaminated into the river. This river is also the major causation toward cholera and typhoid.
Even the fauna of this river has been adversely affected, and notable ones include the Ganges River Dolphin and Ganges River Shark. Nearly 1000 children die each year due to water pollution in India. Currently, there are a few steps taken to drive away from this level and address these issues properly.
Control Measures of Water Pollution
Prevention and control of water pollution could be done in so many ways. To start off, it is to plant more trees around water bodies as they naturally help to assimilate and recycle the pollutants. There is this ‘Water Hyacinth’ that absorbs dissolved toxic substances like cadmium and mercury from water bodies.
It is important to dispose-off waste carefully and not to dump them directly into water bodies, without proper waste treatment. Using natural fertilisers and pesticides as substitutes for chemical ones are good for plants and water. Industries should treat their wastes carefully before disposing of chemicals and other materials into water bodies directly. Even chemical processes such as coagulation, ion exchange method, reverse osmosis, etc. will greatly reduce the level of water pollution.
Lastly, it is better to reduce the consumption of water in our daily activities and reuse water whenever possible to reduce the overall level of pollution.
FAQs on Water Pollution and Its Control Explained
1. What is water pollution according to the CBSE Class 12 syllabus?
Water pollution is defined as any undesirable change in the physical, chemical, or biological properties of water that can cause harmful effects on various living organisms. For the 2025-26 board exams, this primarily refers to the contamination of water bodies like lakes, rivers, oceans, and groundwater by substances produced through human activities, rendering the water unfit for its intended uses.
2. What are the main sources of water pollution from domestic and industrial activities?
The main sources of water pollution can be categorized as follows:
- Domestic Sewage: This includes wastewater from homes and comprises biodegradable organic matter, which leads to a high Biochemical Oxygen Demand (BOD), and pathogenic microbes.
- Industrial Effluents: These are waste products from industries like petroleum, paper manufacturing, metal extraction, and chemical production. They often contain toxic substances, including heavy metals (e.g., mercury, cadmium) and organic compounds.
- Agricultural Runoff: Water flowing from farms often carries fertilizers (containing nitrates and phosphates) and pesticides into nearby water bodies.
- Thermal Pollution: This is caused by hot wastewater from power plants and industries, which reduces the dissolved oxygen content in the water.
3. How does Biochemical Oxygen Demand (BOD) measure the extent of water pollution?
Biochemical Oxygen Demand (BOD) is a measure of the amount of dissolved oxygen required by aerobic bacteria to break down the organic waste present in a certain volume of water. A high BOD value indicates a large amount of biodegradable organic matter in the water, which means the water is highly polluted. Conversely, clean water has a very low BOD. Therefore, BOD acts as a direct indicator of the pollution level in a water body.
4. What is eutrophication and what are its major effects on an aquatic ecosystem?
Eutrophication is the natural aging of a lake or water body due to nutrient enrichment, primarily with nitrogen and phosphorus. When accelerated by human activities (cultural eutrophication), it leads to excessive plant and algal growth (algal blooms). The major effects include:
- A decrease in water quality and clarity.
- Depletion of dissolved oxygen as the algae die and decompose, leading to the death of fish and other aquatic animals.
- Loss of biodiversity in the affected water body.
5. How does biomagnification differ from bioaccumulation, and why is it a significant threat?
Bioaccumulation refers to the buildup of a toxic substance in a single organism over its lifetime. In contrast, biomagnification (or biological magnification) is the increasing concentration of a toxic substance at successive trophic levels in a food chain. It is a significant threat because top predators, including humans, can accumulate dangerously high levels of toxins like mercury or DDT, even if the concentration in the water is low. This can lead to severe health issues, reproductive problems, and ecosystem instability.
6. What are some common examples of water-borne diseases caused by pathogens in polluted water?
Contamination of water with faecal matter can introduce various pathogens, leading to several water-borne diseases. Common examples include:
- Typhoid (caused by Salmonella typhi)
- Cholera (caused by Vibrio cholerae)
- Jaundice (Hepatitis A)
- Dysentery
- Amoebiasis
7. What are the key principles behind controlling water pollution as per the Water (Prevention and Control of Pollution) Act, 1974?
The Water Act, 1974, provides a framework for controlling water pollution based on key principles such as:
- Treating industrial effluents and domestic sewage before they are discharged into water bodies.
- Promoting the reuse and recycling of wastewater to conserve water resources.
- Minimising the use of chemical fertilisers and pesticides in agriculture and encouraging organic farming.
- Implementing integrated wastewater management, combining artificial and natural processes to purify water.
- Strict enforcement of standards for water quality to safeguard aquatic life and public health.
8. Why is an integrated approach to wastewater treatment, like the one used in the town of Arcata, considered a sustainable model?
An integrated wastewater treatment approach is considered sustainable because it combines conventional and ecological methods. In the Arcata, California model, conventional sedimentation and filtration are followed by a series of six connected marshes. These marshes use plants, algae, fungi, and bacteria to naturally neutralise, absorb, and assimilate pollutants. This creates a biodiverse sanctuary that purifies water effectively and at a low cost, turning a waste problem into a valuable ecosystem. It showcases how human-made systems can be integrated with nature for sustainable water management.
9. What is thermal pollution and how does it specifically impact aquatic life?
Thermal pollution is the degradation of water quality caused by any process that changes the ambient water temperature. It is commonly caused by the discharge of hot water from power plants and industrial facilities. This elevated temperature negatively impacts aquatic life by:
- Reducing the concentration of dissolved oxygen (DO), as warmer water holds less oxygen.
- Increasing the metabolic rate of aquatic organisms, which can lead to stress and premature death.
- Encouraging the growth of undesirable algae while harming or killing more sensitive species, disrupting the entire food web.
10. Why is preventing water pollution at the source often more effective than treating polluted water bodies later?
Preventing water pollution at the source is more effective for several reasons. Firstly, it is far more cost-effective to stop pollutants from entering a water body than to fund large-scale, complex cleanup operations. Secondly, once pollutants like heavy metals or persistent organic chemicals enter an ecosystem, they can cause irreversible damage through processes like biomagnification and can persist in sediments for decades. Treating waste at the point of generation is a proactive strategy that protects the entire ecosystem, whereas downstream treatment is a reactive measure that only addresses the symptoms after the damage has already begun.
