CHAPTER 16

ENVIRONMENTAL ISSUES

Syllabus

Environmental issues: Air pollution and its control; water pollution and its control; agro chemicals and their effects; solid waste management; radioactive waste management; green house effect and global warming; ozone depletion; deforestation; any three case studies as success stories addressing environmental issues.

Chapter Analysis

2016 2017 2018

List of Topics D OD D/OD

Air pollution • Cause, effect and control Q 1.Q 1 Q 1 Q 1 Q

method of air pollution (1 M) (3 M) (1 M) (3 M)

• Electrostatic precipitator Advantages of CNG over diesel

Water pollution • Integrated waste water 1 Q

treatment (2 M)

Agro chemicals • Biological oxygen demand 1 Q 1 Q 1 Q

and their • Algal bloom and its effect (1 M) (2 M) (3 M)

effects Ozone • Chlorofluorocarbon (CFCs) 1 Q 1 Q

depletion • Relationship between (2 M) (2 M)

CFCs and ozone

• From the above analysis, it can concluded that important topics from this chapter from exam point of view are air pollution (its causes, effect and control measures), electrostatic precipitator, concept of integrated waste water treatment, significance of BOD, Algal bloom and its effect on aquatic organisms, and concept of ozone depletion (relationship between CFCs and ozone).

TOPIC-1

Pollution, Solid and Radioactive Wastes

Revision Notes

> Introduction

• Human population explosion increases the demand for food, water, home, electricity, roads, automobiles, etc.

It leads to pollution of air, water and soil and depletion of valuable natural resources.

• Pollution is any undesirable change in physical, chemical or biological characteristics of air, land, water or soil.
• Agents that cause pollution are called pollutants.

TOPIC - 1 Pollution, Solid and Radioactive Wastes .... P. 378

TOPIC - 2 Greenhouse Effect, Global warming and Ozone

Depletion .... P. 391

379 ENVIRONMENTAL ISSUES

• The Government of India has passed the Environment (Protection) Act, 1986 to control environmental pollution and protect and improve the quality of our environment.

Air Pollution and Its Control

Causes of Air Pollution

• Particulate and gaseous air pollutants from smoke stacks of thermal power plants, smelters and other industries release particulate and gaseous air pollutants.

According to Central Pollution Control Board (CPCB), particulate size of less than 2.5 mm in diameter (PM 2.5) causes greatest harm to human health.

Pollutants from automobiles.

Use of leaded petrol.

<math>\triangleright</math> Harmful Effects of Air Pollution

• Air pollutants cause injury to all living organisms.
• They reduce growth and yield of crops and cause premature death of plants.
• Air pollutants affect the animals and humans respiratory system.

It causes respiratory problems, irritation, inflammations and damage to lungs and premature deaths.

Control of Air Pollution

1. Particulate matters must be separated/filtered out before releasing the harmless gases into the atmosphere.
2. Use of catalytic converters (having Platinum-Palladium & Rhodium as the catalysts).

• It reduces emission of poisonous gases.

This converts unburnt hydrocarbons to CO₂ and water, and carbon monoxide and nitric oxide to CO₂ and nitrogen gas, respectively.

• Motor vehicles having catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.

1. Proper maintenance of automobiles along with use of lead-free petrol or diesel can reduce the pollutants they emit.
2. Catalytic converters, having expensive metals namely platinum-palladium and rhodium as the catalysts, are fitted into automobiles for reducing emission of poisonous gases.
3. Phasing out of old vehicles
4. Use of low-sulphur and aromatic content in petrol and diesel
5. Application of pollution-level norms for vehicles, etc.

> Controlling Vehicular Air Pollution : A Case Study of Delhi

• In Delhi, compressed natural gas (CNG) in public transport (buses) is used.

CNG is better than petrol and diesel because—

1. CNG burns most efficiently and very little of it is left unburnt.
2. CNG is cheaper than petrol or diesel, cannot be siphoned off by thieves and adulterated like petrol or diesel.

• The main problem with CNG is-

1. The difficulty of laying down pipelines to deliver
2. Distribution points/pumps and ensuring uninterrupted supply.

Electrostatic Precipitator

It is the electrical device widely used to remove particulate matter present in the exhaust of thermal power plants and vehicular exhaust.

• It can remove over 99% particulate matter present in the exhaust from a thermal power plant.
• The electrons released from electrode wires (maintained at several thousand volts) attach to dust particles and give a negative charge.
• The collecting plates are earthed so that they attract the charged dust particles.
• The velocity of air between the plates must be low enough to allow the dust to fall.
• A scrubber removes gases like SO₂.
• In a scrubber, the exhaust is passed through a spray of water or lime.
• Very small particulates are not removed by this precipitator.

Laws & policies in India to control vehicular pollution

(a) Auto fuel policy

• It has laid out a roadmap to cut down vehicular pollution in Indian cities. It has steadily reduced the sulphur and aromatic content in petrol and diesel fuels.

(b) Euro II norms

• It stipulates that sulphur should be at 350 parts-per-million (ppm) in diesel and 150 ppm in petrol.
• Aromatic hydrocarbons are to be contained at 42% of the concerned fuel.