Q.1. Define pollution and pollutant. (AKTU. - 2014 - 15)
Ans. Pollution And Pollutant: -
In a
homeostatic ecosystem there is a balance between the living organisms and the
environment. Disturbance in any component of the environment is likely to have
a harmful effect on the ecosystem. Any change in the environment which
contributes to its deterioration is called pollution of the environment and the
agent which causes the pollution is called pollutant. This change in the physical,
chemical or biological characteristics of our physical environment (air, water
and land) is undesirable and harms human life, other living organisms and
cultural assests. The resulting impact on the environment has been so massive
with far reaching consequences that the very existence of life is threatened.Q.2 What do you mean by water pollution? Discuss its major sources and effects. Discuss in brief the various processes of water treatment with layout of a water treatment plant. (AKTU. - 2005-06)
Related Questions -
Q. What is
water pollution? What are its effects on human health? (AKTU. - 2010 - 11)
Q. What is water
pollution? Briefly discuss the major sources of water pollution. (AKTU. - 2011 - 12)
Q. Enumerate
various types of pollutants that cause pollution of water bodies.
(AKTU. - 2012 -13)
Ans. Water Pollution:
- (AKTU. - 2006-07, 08-09)
Generally speaking, water pollution is a
state of deviation from the pure condition, where by its normal properties and
functions are affected.
Water
pollution can be defined as the presence in water, of some foreign substance or
impurities (organic, inorganic, radiological or biological) in such quantity so
as to constitute a health hazard by lowering the water quality and making it
unfit for use.
Major sources of water pollution: -
The main sources of water pollution are
natural, agricultural, mining, municipal, industrial and accidental:
1. Natural
pollution may be due to aerial contaminants entering the water body due to
rainfall or melting of ice. Decaying of plants, animals and organic matter;
leachates from animal excreta will introduce micro-organisms in water.
2. Agricultural
pollution of water will be due to soil and silt washings from land surfaces,
fertilisers, insecticides, pesticides and weed killers.
3. Mining
pollution of water will be due to fines or tailings from ore washing, inert
suspended solids, soluble toxic materials and acid drainage.
4. Municipal
pollution of water will be due to sewage obtained from domestic premises, institution,
commercial and industrial buildings.
5. Industrial
pollution of water will be due to the effluents coming from various industries
such as food and drugs, chemical, materials and energy.
6. Accidental
spillage of chemicals during loading and transit; and accidental leakage from
industrial storage tanks, oil refineries etc.
The sources of water pollution can divided into two categories,
namely point sources and diffused sources.
Point sources: -
Those sources which can be readily
identified at a single location are known as point sources. For instance -
industries, municipal sewage, treatment plants, combined sewer overflow, raw
sewage discharges etc.
Diffused Sources: -
Diffused
sources or non-point sources are the sources of generalized discharge of waste
water whose location cannot be easily identified. Here, the pollutants
scattered on the ground ultimately reach the water sources and cause water
pollution. For instance - run-off from agriculture lands, forestry, mining,
construction, etc.
Effects of Water Pollution: -
The adverse
effects of water pollution can be studied under the following heads:
(i) Physical Effects: -
These will be due to suspended particle
solids, cooling water from power stations and oily surface of films. Solids may
be inert material wastes or insoluble finely divided organic solids.
Cooling water
from power stations can cause a rise in water temperature and bring about
thermal pollution. Variations in temperature will affect the metabolic rate of
physiological processes. Increased temperature will cause decrease in fresh
water fauna population and increase in flora population.
Waste oil,
fats and grease can enter water from several sources. These will form a thin
film on the water surface which prevents the exchange of oxygen with the
atmosphere causing reduction of water oxygen saturation.
(ii) Oxidation Effects: -
There are two types of oxidation namely:
(a) Oxidation by the
action of bacteria upon organic pollutants.
(b) Chemical oxidation
of other pollutants.
Both types of oxidation involves the use of dissolved oxygen.
(iii) Toxic Chemical Effects: -
Some organic
and inorganic chemical substances are toxic to plants, animals and humans.
These toxic substances are absorbed into the tissues from polluted water. They
can cause injury leading to death of living organisms. The effects will depend
upon the concentration, period of action and the metabolism of the organism.
(iv) Chemical Nutrient Effects: -
Chemical nutrients are required by plants
and animals for maintaining their growth and metabolism. Nitrates and
phosphates occur in water in small quantities. These are sufficient to maintain
balanced biological growth. The nutrient levels slowly rise as a result of the
bio-degradation of dead organic material. This rise in nutrients is called
ageing or eutrophication.
(v) Micro-organism Effects: -
Wastes that are discharged into water
contain pathogenic organisms that are capable of transmitting human diseases.
Bacteria are responsible for cholera, typhoid fever, bacillary dysentery,
gastroenteritis. Virus may cause poliomyelitis, infective hepatitis, and echo
and consackil fevers. Round worm, beef and pork tape worms may also cause
diseases.
