Engineering Chemistry S Datta

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Pollution Prevention and Waste Minimisation
Pollution may be defined as “the excessive discharge or addition of undesirable substances or
unwanted foreign matters into the environment, thereby adversely altering the natural quality
of the environment, and causing damage to human, plant or animal life”. Using the term
environment we mean air, water and soil.
Our environment is a complex and dynamic system involving all forms of life which are
virtually inter-dependent. Human being, the best form of life on earth, is ruling the earth and
for his comfort, power and thirst for knowledge has been constantly changing the natural
characteristics by adding toxic components to the environment and as a consequence every
living organism is facing environmental hazards. The principal causes of these hazards are
(i) population explosion, (ii) deforestation and depletion of forest cover, (iii) rapid urbanisation,
(iv) depleting surface and ground water rapidly, (v) emission of heat, particles and toxic gases
from industries, (vi) no recycling of waste products. Apart from all these man-made problems
natural factors like volcanic erruptions, radioactivity and natural disasters also contribute to
pollution.
AIR POLLUTION
Air is a mixture of gases that form the atmosphere. The clean air is composed of the
gases having concentration
O 2
→ 20.92%, N 2
→ 78.1%, Ar → 0.9325%
CO 2
→ 0.03%, H 2
→ 0.01%, Ne → 0.0018%
He → 0.0005%, Kr → 0.0001%
Air pollution has become an important factor of environmental degradation. The
increasing industrialisation, urbanisation, excessive burning of fuel etc. produce a large amount
of polluting substances, that have damaging effect to human, plants and animal lives. Diseases
like bronchial asthma, lung cancer, heart and brain damages etc. have become prevalent due
polluted air.
Air Pollutants
Air pollutants are either in solid, liquid or gaseous forms. According to mode of formation,
pollutants which enter the air directly are called primary pollutants, and those which are
created in the air from pollutants under electromagnetic radiation from the sun are called
secondary pollutants.
(i) Carbon monoxide (CO)
Carbon monoxide is a colourless, odourless, highly toxic gas released by the partial
combustion of fuels from automobile, industries, oil refineries, coals, woods etc. About 290
million tonnes of CO is discharged into the atmosphere annually, 90% of which originates from
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