Pollution of Air and Water - Class 8 Notes & Olympiad Questions

Pollution

Pollution refers to the existence of harmful or poisonous substances in the environment at abnormally high levels.
These substances, known as pollutants, can contaminate the air, water, and land, causing adverse effects on the environment, living organisms, and human health.

Air Pollution - Causes and Sources

a) Air pollution occurs when harmful gases, particles, and other substances are present in the air at levels that can be detrimental to human health and the environment.
b) These pollutants include gases such as sulphur dioxide, nitrogen oxides and carbon monoxide, as well as particulate matter like smoke and dust.
c) The sources of these pollutants can vary, including industrial processes, vehicle emissions, burning of fossil fuels, and natural sources.

Effects of Air Pollution

a) Sulphur Dioxide (SO₂): Produced from burning coal and other fossil fuels in power plants, industrial facilities, and manufacturing processes, sulphur dioxide is harmful to our respiratory system, causing lung issues. When it reacts with water vapour in clouds, it forms sulphuric acid, which leads to acid rain.

b) Nitrogen Dioxide (NO₂₎: Emitted by burning fuels like petrol and diesel, nitrogen dioxide irritates the eyes and impacts lung health. It contributes to acid rain when present in the atmosphere and can lead to respiratory issues.

c) Carbon Monoxide (CO): Incomplete combustion of fuels like wood, coal, petrol, and diesel produces carbon monoxide, a poisonous gas that binds to haemoglobin in our blood, preventing it from carrying oxygen. High levels can cause suffocation and death.

d) Carbon Dioxide (CO₂): Although not directly harmful at normal levels, excess carbon dioxide in the atmosphere is considered a pollutant as it contributes to the greenhouse effect and global warming, causing climate change.

e) Chlorofluorocarbons (CFCs): These chemicals, used in refrigeration, air conditioning, and aerosols, are responsible for depleting the ozone layer in the upper atmosphere. This depletion allows harmful ultraviolet rays to reach the Earth's surface, increasing the risk of skin cancer.

f) Suspended Particulate Matter (SPM): Fine solid or liquid particles suspended in the air, such as dust, smoke, and fly ash, are collectively known as SPM. These particles can cause respiratory diseases and interfere with photosynthesis, affecting plant growth and ecosystems. The incomplete combustion of fuels like wood, coal, and diesel produces fine particulate matter that becomes suspended in the air.

Greenhouse Effect and Global Warming

a) When solar radiation from the sun enters Earth's atmosphere, some of it is reflected back into space, while some are absorbed by the surface and warm it. Part of this absorbed heat is re-radiated as infrared radiation.
b) Greenhouse gases in the atmosphere, such as carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), chlorofluorocarbons (CFCs), and water vapour (H₂O), trap some of this infrared radiation, preventing it from escaping into space. This trapped heat warms the atmosphere, similar to how a greenhouse keeps plants warm.
c) The natural greenhouse effect is essential for maintaining a stable temperature on Earth, allowing life to thrive in a habitable environment.
d) However, due to human activities like burning fossil fuels (coal, oil, and natural gas), deforestation, and industrial processes, the concentration of greenhouse gases, particularly carbon dioxide, has increased significantly in the atmosphere.
e) This enhanced greenhouse effect leads to excessive warming of the Earth's atmosphere, a phenomenon known as global warming.
f) Global warming has various consequences, including the melting of polar ice, rising sea levels, changes in weather patterns, shifts in ecosystems, and more frequent and severe weather events.

Steps to Prevent Air Pollution

a) Switch to Clean Fuels: Replace traditional fuels like coal and diesel with cleaner alternatives such as LPG (liquefied petroleum gas) and CNG (compressed natural gas) for cooking and transportation. These fuels produce fewer harmful emissions.

b) Use Renewable Energy: Transition to non-polluting sources of energy like solar energy, wind energy, and hydropower for generating electricity. These sources don't emit harmful pollutants or greenhouse gases.

c) Composting Instead of Burning: Instead of burning leaves, agricultural waste, or other organic materials, convert them into compost through proper composting methods. Burning releases pollutants into the air and contributes to air pollution.

d) Afforestation and Reforestation: Planting more trees and restoring forests helps absorb carbon dioxide from the atmosphere, acting as a natural filter for air pollutants. Trees also release oxygen, improving air quality.

Water Pollution

a) Water pollution refers to the contamination of water bodies such as rivers, lakes, ponds, oceans, and groundwater with harmful substances. These substances, known as pollutants, can have detrimental effects on aquatic ecosystems, the environment, and human health.
b) Water pollution can be caused by various human activities and natural processes, leading to the degradation of water quality and impacting the organisms that rely on these water sources.
c) Preventing and addressing water pollution is crucial to maintaining the health of aquatic ecosystems and ensuring access to safe and clean water for both human consumption and ecological balance.

Causes of Water Pollution

a) Dumping of Untreated Sewage into Rivers: When untreated sewage, human waste, and other contaminants are discharged directly into rivers and water bodies without proper treatment, it can contaminate the water and make it unsafe for consumption. Pathogens and disease-causing microorganisms present in untreated sewage can lead to waterborne diseases like cholera, typhoid, diarrhoea, and dysentery when people come into contact with or consume the contaminated water.

b) Discharging of Untreated Industrial Wastes: Industries often generate various chemicals and waste products as byproducts of their processes. If these wastes are released into water bodies without proper treatment, they can poison aquatic life and impact the overall water quality. Polluted water can harm fish populations, disrupt ecosystems, and pose health risks to humans who rely on the water for various purposes.

c) Use of Pesticides and Fertilisers in Agriculture: Agricultural activities involve the use of pesticides and fertilisers to enhance crop growth and protect them from pests. However, excess use of these chemicals can result in runoff into nearby water bodies. This runoff carries pesticides and fertilisers with it, leading to water contamination. These chemicals can harm aquatic organisms, disrupt aquatic ecosystems, and contaminate drinking water sources.

d) Industrial Spills: Accidental spills of hazardous chemicals from industries or transportation can lead to the release of pollutants into water bodies. These spills can have immediate and long-term effects on water quality, aquatic life, and human health. Cleaning up such spills can be challenging and may result in lasting damage to the ecosystem.

e) Improper Waste Disposal: Improper disposal of household waste, plastic, and other pollutants can lead to their entry into water bodies through stormwater runoff. These pollutants can persist in the water, affecting aquatic organisms and making the water unsuitable for various uses.

f) Erosion and Sedimentation: Soil erosion from construction sites, deforested areas, and agricultural lands can lead to sedimentation in water bodies. Sediments can carry pollutants like heavy metals and nutrients into water sources, degrading water quality and impacting aquatic habitats.

g) Oil Spills: Oil spills from ships, pipelines, or other sources can have severe consequences for aquatic ecosystems. Oil spills coat the water surface, suffocating aquatic organisms and causing long-lasting environmental damage.

Steps to Prevent Water Pollution

Preventing water pollution requires a combination of regulations, proper waste management, responsible industrial practices, and public awareness. Safeguarding water quality is crucial for the well-being of both ecosystems and human communities that rely on clean water sources.

a) Proper Waste Disposal: Ensure that household waste, including plastics, chemicals, and other pollutants, is properly disposed of in designated waste bins or recycling centres. Avoid throwing waste into open drains, water bodies, or public spaces.

b) Avoid Littering: Be responsible with waste disposal, especially in outdoor areas. Don't litter on beaches, in parks, or alongside roads, as wind and rain can carry litter into water bodies.

c) Reduce Chemical Usage: Minimize the use of household chemicals, pesticides, and fertilisers. When you do use them, follow instructions carefully to prevent excess chemicals from entering the water system through runoff.

d) Promote Eco-Friendly Products: Choose eco-friendly and biodegradable products whenever possible to reduce the potential for pollutants to enter water bodies.

e) Rainwater Harvesting: Collect rainwater for non-potable uses such as watering plants, flushing toilets, and washing vehicles. This reduces the demand on freshwater resources and helps prevent runoff pollution.

f) Sewage Treatment: Ensure that sewage from homes, industries, and commercial establishments is treated properly before being discharged into water bodies. Proper treatment can remove harmful pathogens and pollutants.

g) Industrial Regulations: Implement and enforce stringent regulations on industries to ensure they properly treat their waste before releasing it into water bodies. Regular monitoring and penalties for non-compliance can deter pollution.

h) Public Awareness: Educate communities about the importance of clean water and the steps they can take to prevent pollution. Campaigns, workshops, and educational programs can raise awareness and encourage responsible behaviour.

By adopting these measures, individuals, communities, industries, and governments can collectively contribute to preventing water pollution and ensuring the availability of clean and safe water for current and future generations.

Conservation of Water

Conserving water is crucial for sustainable resource management. Here are a few more steps you can take to conserve water:

a) Fix Leaks: Regularly check for and fix leaks in faucets, toilets, and pipes. Even a small leak can waste a significant amount of water over time.

b) Install Water-Saving Fixtures: Install low-flow faucets, showerheads, and toilets to reduce water consumption without compromising functionality.

c) Shorter Showers: Take shorter showers to reduce water use. Consider turning off the water while soaping up and then turning it back on to rinse.

d) Sweep, Don't Hose: Instead of using a hose to clean driveways or sidewalks, use a broom. It saves water and prevents unnecessary runoff.

e) Mulching: Apply mulch to the soil surface in gardens and around plants. This helps retain moisture and reduces the need for frequent watering.

f) Water Plants Wisely: Water plants during the early morning or late afternoon when evaporation rates are lower. Avoid watering on windy days to prevent water wastage.

g) Collect Cold Water: Collect the cold water that flows before the tap heats up, and use it for tasks like watering plants or cleaning.

h) Greywater Reuse: Reuse greywater (water from showers, sinks, and washing machines) for irrigation purposes after proper treatment.

i) Educate and Advocate: Raise awareness about water conservation in your community. Encourage others to adopt water-saving practices and advocate for water conservation measures.

j) Responsible Recreation: Be mindful of water use during recreational activities, such as using water responsibly while swimming or playing in pools.

k) Support Water Conservation Initiatives: Support and participate in local and national water conservation campaigns and initiatives.

Purification of Water

Ensuring access to safe and potable water is essential for maintaining public health. Some methods to purify water and make it safe for consumption are:

a) Filtering: Filtration is a process that removes particles and impurities from water. There are various types of filters, such as activated carbon filters, ceramic filters, and reverse osmosis filters, that can effectively remove different contaminants. These filters work by physically trapping particles or adsorbing chemicals and substances that may be harmful or affect the taste and odour of water.

b) Boiling: Boiling water is a simple and effective method to kill harmful microorganisms, such as bacteria, viruses, and parasites, that can cause waterborne diseases. Bringing water to a rolling boil for at least one minute (or longer at higher altitudes) ensures that most pathogens are destroyed. However, boiling does not remove chemical pollutants.

c) Chlorination: Adding chlorine to water is a common method of disinfection used by water treatment plants. Chlorine kills bacteria, viruses, and other harmful microorganisms present in water. It also helps prevent the growth of bacteria in the distribution system, ensuring that water remains safe as it travels to consumers. However, excessive use of chlorine or inadequate treatment can lead to the formation of disinfection byproducts that may be harmful.

Water Treatment Plants

Water treatment plants play a crucial role in ensuring that water from various sources, such as rivers, lakes, or groundwater, is treated to meet safe drinking water standards.
The steps involved in working on a water treatment plant are:

a) Pre- Sedimentation and Decantation (optional): This is the step where water is allowed to stand in a large settling basin. During this process, larger and heavier particles, including sand, silt, and other suspended solids, settle to the bottom of the basin due to gravity. This process helps remove larger impurities from the water.

b) Coagulation: Coagulation is the first step in water treatment. In this process, chemicals known as coagulants, often aluminium sulfate (alum) or ferric chloride, are added to the water. These coagulants neutralize the negative charges on suspended particles and colloids, causing them to come together and form larger particles called flocs. Coagulation prepares the water for subsequent processes by aiding in the removal of particles that are too small to settle on their own.

c) Flocculation: After coagulation, the water enters the flocculation stage. During flocculation, gentle mixing or agitation is applied to the water to encourage the formation of larger and heavier flocs. The flocs continue to grow in size as they collide and attach to each other. Flocculation enhances the ability of suspended particles to settle during sedimentation.

d) Sedimentation: The water then moves into a sedimentation basin, where the flow is slowed down significantly. Due to the increased size and weight of the flocs formed during flocculation, they settle under the force of gravity to the bottom of the basin. This process separates the suspended particles from the clear water above. The settled particles, known as sludge, are removed from the bottom of the basin.

e) Filtration: Following sedimentation, the water undergoes filtration to further remove remaining suspended particles and any fine flocs that might not have settled completely. The water passes through layers of granular media, such as sand, gravel, and anthracite coal, in a filter bed. These materials trap and remove smaller particles, ensuring that the water becomes clearer and cleaner.

f) Disinfection: Once filtered, the water is disinfected to eliminate harmful microorganisms that may still be present. Chlorine, chloramines, or other disinfectants are added to the water to kill or inactivate bacteria, viruses, and other pathogens. This step ensures that the treated water is safe for consumption and meets regulatory standards.

g) Fluoridation (Optional): In some areas, fluoride is added to the water at controlled levels to prevent dental cavities and promote oral health.

h) Storage and Distribution: After disinfection, the treated water is stored in reservoirs or storage tanks. This provides a buffer to meet fluctuations in water demand and ensures a continuous supply to consumers. From the storage facility, the water is distributed through a network of pipes to homes, businesses, and other users.