Preventive Measures Chapter Notes | Geography Class 9 ICSE PDF Download

Pollution is a growing threat to our planet, affecting the air we breathe, the water we drink, and the soil that sustains life. In the chapter "Preventive Measures" from ICSE Class 9 Geography, we dive into practical and effective strategies to combat various forms of pollution. From controlling harmful emissions in industries to managing waste responsibly, this chapter equips us with the knowledge to protect our environment. Imagine a world where clean air, pure water, and fertile soil are preserved for future generations—this chapter shows us how to make that vision a reality through innovative techniques and mindful practices.

Air Pollution

• Air pollution is a major issue in many cities, requiring urgent action to reduce its impact.
• Two main approaches are used to tackle air pollution: source correction methods and pollution control equipment.

Source Correction Methods

• Focuses on reducing pollution at its origin to prevent harmful emissions.

Change in Raw Materials:

• Use eco-friendly raw materials to minimize pollution.
• Replace coal and diesel with liquefied petroleum gas (LPG) or compressed natural gas (CNG) to lower emissions.
• Use fuels with low sulfur content instead of high-sulfur fuels.
• Install catalytic converters to reduce hydrocarbon and carbon monoxide emissions.

Example: A factory switches from high-sulfur coal to CNG for its boilers, significantly reducing sulfur dioxide emissions that cause acid rain.

Change in Process:

• Modify production processes to decrease atmospheric pollutants.
• Use absorption to remove gaseous pollutants like sulfur dioxide, chlorine, and nitrogen oxides by dissolving them in water or caustic soda.
• Apply absorption to treat wastewater by attaching pollutants to activated carbon, which is then processed with steam or carbon dioxide for purification.

Modify the Existing Equipment:

• Alter equipment to control pollution levels.
• Replace open hearth furnaces with electric or basic oxygen furnaces to reduce smoke and carbon emissions.
• Use floating roof covers on tanks in petroleum refineries to minimize hydrocarbon loss.

Maintenance of Equipment:

• Regularly maintain energy-intensive equipment to reduce fumes.
• Fix leakages in tanks to prevent pollutant release.

Pollution Control Equipment

• Devices are designed to control both gaseous and solid particle pollutants in the air.
• Key factors to consider when selecting equipment:
  • Volume of particulate matter to be handled.
  • Chemical and physical properties of particulates, including size.
  • Temperature and humidity of the gaseous medium.
  • Concentration of gases in particulate matter.
• Devices are divided into two types: those controlling particulate contamination and those controlling gaseous contamination.

Pollution Control Devices and Their Functioning

Filters:

• Used in power plants to trap particulate matter from gases.
• Smoke passes through cloth bags, capturing particulates.

Gravitational Settling Chamber:

• A rectangular chamber with horizontal trays where polluted gas moves slowly.
• Low velocity allows particulates to settle due to gravity.
• High-density pollutants collect at the bottom for removal.

Example: In a cement factory, a gravitational settling chamber captures heavy dust particles from exhaust gases, preventing them from polluting the air.

Scrubber:

• A wet scrubber traps water-soluble gases like sulfur dioxide, nitrogen oxide, and ammonia.
• Water is sprayed downward through nozzles, colliding with rising polluted gases.
• Particulate-laden water droplets settle at the bottom, separating pollutants.

Electrostatic Precipitator:

• Removes fly ash from coal or material combustion.
• Polluted gas enters the device, where it becomes negatively charged.
• Charged particles are attracted to positively charged electrode plates and deposited.
• Impurities are dislodged by mechanical rappers and collected in a hopper.
• Removes over 99% of impurities, making it highly efficient.

Cyclone Separator:

• Removes impurities and particulates from dust-laden air.
• Air enters a conical metallic cylinder at high speed, creating a vortex.
• Particulate matter falls to the bottom, and clean gas exits upward.
• Pollutants slide down the cylinder walls and are discharged.

Water Pollution

• Water pollution is addressed by managing non-point and point sources and treating wastewater.

Non-Point Sources

Pollutants enter water bodies over a large area, e.g., agricultural runoff.
Steps to reduce non-point source pollution:

• Build separate drainage systems for sewage and rainwater to prevent overflow.
• Plant nitrogen-fixing plants to reduce chemical fertilizer use.
• Use agrochemicals and pesticides carefully to avoid water body contamination.
• Prevent manure runoff into water sources.
• Use biofertilizers and biopesticides instead of chemical alternatives.

Example: A farmer plants clover, a nitrogen-fixing plant, to reduce fertilizer use, preventing excess nitrates from washing into nearby rivers.

Point Sources

Pollutants are discharged at specific locations, e.g., factory effluents into rivers.
Steps to control point source pollution:

• Treat wastewater before discharge.
• Enforce strict laws with penalties for releasing untreated wastewater.

Treatment of Plants

• Wastewater undergoes three treatment stages: primary, secondary, and tertiary.

Primary Treatment

• Involves screens, grit chambers, and sedimentation tanks arranged in sequence.
• Water is treated with chlorine gas to kill harmful bacteria.
• Dissolved organic matter like salts remains untreated in this stage.

Secondary Treatment

• Organic matter is broken down by microorganisms.
• Water enters a tank with microorganisms, and air is supplied through diffusers.
• Microorganisms degrade organic matter in the presence of oxygen.
• Impurities settle at the tank bottom and are removed.
• Water is treated with chlorine gas to eliminate remaining harmful organisms.

Tertiary Treatment

• Removes nutrients like nitrogen and phosphorus.
• Treated water can be reused for industrial, agricultural, or domestic purposes.

Methods to Control Soil Pollution

• Soil pollution is managed through various waste disposal and treatment methods.

Open Dumping

• Wastes are dumped in open areas away from cities.
• Unsafe method due to breeding of mosquitoes and flies.
• Burning wastes causes air pollution, and rainwater can carry pollutants to water bodies.

Sanitary Landfills

• Wastes are disposed in layers, compacted, and covered with soil for bacterial decomposition.
• Prevents attack by rodents or insects.
• Avoid locating landfills in areas with high groundwater levels to prevent contamination.

Composting

• Household and municipal wastes are decomposed aerobically by microorganisms.
• Produces humus, which enhances soil fertility.
• Example: A community composts kitchen waste, turning it into nutrient-rich humus for local gardens.

Incineration

• Municipal wastes are burned at high temperatures.
• Unburnt materials like metals are recycled.
• Produces fly ash and sulfur dioxide, polluting the air.
• Expensive due to the need for air pollution control devices.

Segregation

• Wastes like clothes, paper, glass, and metals are sorted into separate bins for recycling.
• Effluents should be treated before soil discharge.
• Use biofertilizers and manures instead of chemical fertilizers.

Methods to Control Radioactive Pollution

Steps to manage nuclear pollution:

• Minimize use of X-rays.
• Regularly inspect nuclear reactors for safety.
• Test nuclear devices deep underground.
• Reduce production of radioisotopes.
• Use wet drilling and underground drainage in nuclear mines.
• Handle nuclear wastes carefully, storing them in shielded, corrosion-proof containers buried deep underground for safe decay.
• Maintain radiation levels within safe limits.
• Build radiation-resistant walls near nuclear reactors.
• Dispose of radioactive wastes under approved rock and soil.

Example: A nuclear power plant stores radioactive waste in shielded containers buried deep underground to prevent environmental contamination.