Ganga. It is the most polluted river in India.
In fact according to a recent study by
World Wide Fund for nature, Ganga is
considered to be one of the 10 most
endangered rivers in the world. But it's
not only Ganga that is polluted. There
are many other water bodies that have
been polluted because of water pollutants.
Let us study about these water
pollutants in this lesson. The main water
pollutants are the harmful chemicals
that are discharged by industries
directly into the rivers and streams.
These industries include oil refineries,
paper factories, textile and sugar mills,
chemical factories etc. All of these
cause chemical contamination of water.
Industries release chemicals like
arsenic, leads and fluorides into the
water bodies. All these chemicals cause
toxicity in plants and animals. The
impure water also affects the soil. It
changes the acidity of the soil. Due to
which the growth of worms, plants,
everything is affected. But there are
regulations to prevent this. Industries
are supposed to treat the waste produced,
to reduce the toxicity before
discharging it into the water bodies.
But often the rules are not followed.
Other pollutants are weedicides and
pesticides. These are very important for
production of crops but when they are
washed away from the field, they dissolve
in water bodies and pollute the
water. They sometimes also seep into the
ground and pollute the groundwater. These
chemicals which get washed away from the
fields, also affect water bodies like
You must have seen a pond which looks
green from a distance that is because
growth of a lot of algae in it.
Excessive quantity of chemicals act as
nutrients to these algae. When these
algae die, they serve as a food for
decomposers like bacteria. A lot of
oxygen from the
water is used up in this process. This
leads to decrease in oxygen level in the
water that can kill even the aquatic
organisms. The next water pollutant that
we will be talking about is sewage.
Sewage contains food waste, detergents,
microorganisms etc. So it has to be
treated before it is disposed.
But sometimes untreated sewage is thrown
directly into the rivers.
This causes water to contaminate and
such water which is contaminated by
sewage may contain bacteria, fungi,
parasites, viruses which cause diseases
like typhoid, cholera and jaundice. Untreated
sewage is sometimes disposed in soil which
leads to the pollution of groundwater.
Other pollutants are bacteria produced
by faeces of mammals. When people start
defaecating in the river, these bacterias
get mixed with water and contaminate the
water and if we consume such water we
might get infections. Even hot water can
be a pollutant. Usually this hot water is
disposed in the river by industries and
power plants. It raises the temperature
of the water in the water body which
leads to adverse effects on aquatic
animals and plants living in it.
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Class 8 - Pollution in Water
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