Thermal pollution occurs when the temperature of water bodies increases due to the release of heated water from industrial and power generation processes. Coal-fired power plants, nuclear power plants, hydroelectric plants, textile mills, and other industries withdraw large amounts of water for cooling purposes and then discharge it at higher temperatures back into rivers, lakes, and streams. This warms the surface water and can negatively impact aquatic life by decreasing oxygen levels and interfering with reproduction. Methods to control thermal pollution include requiring industries to use cooling towers, ponds, or artificial lakes to lower the temperature of wastewater before releasing it.

1. SHRI JAI NARAIN P. G. COLLEGE
LUCKNOW

2. Presented by – SHIVANAND JAISWAL
BSc – III YEAR BOTANY

3. THERMAL POLLUTION
 Thermal pollution is increase in temperature of air
and water by heat.
 Many industries generate their own power and use
water to cool their generator. This hot water is
released into the system from where it was drawn ,
causing a warming trend of surface water. If the
system is poorly flushed , a permanent increase in the
temperature may result.

4. SOURCES
The various causes
or sources of
thermal pollution
are as follows –
1. INDUSTRIES

5. a) Coal – Fired Power Plants -
some thermal power plants
use coal as fuel . Coal –
fired power plants
constitute the major source
of the thermal pollution.

6. b) Nuclear Power Plants –
Nuclear Power Plants emit a
large amount of unutilized
heat and traces of toxic radio
nuclear into nearby water
streams which may responsible
for increasing the temperature
of water bodies.

7. c) Hydro-Electric power –
Generation of hydro-electric power also
results in negative thermal loading of
water bodies.

8. D) INDUSTRIAL
EFFLUENTS –
Textile , paper and pulp
industries generating
electricity require large
amount of cooling water
for heat removal.

9. 2. DOMESTIC SEWAGE –Domestic sewage is often
discharged into rivers ,
lakes , streams without
waste treatment . The
municipal water sewage
normally has a higher
temperature $ less
dissolved oxygen content
(DO) and the demand of
oxygen increases .

10. 3. DEFORESTATION -
When deforestation takes
place , the water bodies are
directly exposed to sunlight ,
thus absorbing more heat and
raising its temperature .
Deforestation is also a main
cause of the higher
concentration of greenhouse
gases i.e. global warming in
the atmosphere .

11. EFFECTS OF THERMAL
POLLUTION
 Decrease in DO (oxygen) levels –
Elevated temperature decreases the level of DO
(dissolved oxygen) in water. The warm water holds
less oxygen than cold water. The decrease in DO
can create suffocation for plants and animals such
as fish and amphibians.

12.  Increase in toxin –
With the constant flow of high
temperature discharge from industries,
there is a huge increase in toxin which may
contain chemical or radiation that may
have harsh impact on the ecology and
make them susceptible to various diseases.

13.  Ecological impact –
Many aquatic species are
sensitive to small temperature
changes such as one degree
Celsius that can cause
significant changes in
organisms metabolism and
other adverse cellular biology
effects.

14.  Migration –
The warm water can also cause particular
species of organisms to migrate to suitable
environment to their survival this can
results in loss for those species that depend
on them for their daily food as their food
chain is interrupted.

15.  Interference with reproduction –
In fishes, several activities like nest
building, spawning, hatching, migration
and reproduction etc. depends on some
optimum temperature but, the warm water
not only disturbs spawning, but also
destroys the laid eggs.

16. CONTROLS
Thermal pollution can be controlled by following
methods –
 By making awareness among the people about the ill
effects of thermal pollution .
Rules can be applied on the industries due to which they
cannot discharge hot water directly in the water bodies .

17. Cooling towers -
These cooling towers are
the devices which transfer
waste heat to the
atmosphere by evaporation
these take up less area
than the ponds.

18.  COOLING PONDS –
Cooling ponds are the best way
to cool thermal discharges.
These are man made water
bodies designed for cooling of
water by evaporation,
convention & radiation.

19.  Artificial lakes – Artificial lakes are the man
made water bodies in which
heated effluents can be
discharged into the lake at
one end and water for
cooling purposes may be
withdrawn from the other
end.

20.  Spray ponds –
Here the water is sprayed through
nozzles where fine droplets are formed.