When there is an increase in the temperature of water bodies by
industrial processes or activity of
thermal power stations it is referred to
as thermal pollution. The heated water
causes a lowering of dissolved oxygen
(DO) level in the body of water. As the
DO content decreases the demand of
oxygen increases in the water body,
creating anaerobic conditions thereby
disrupting the ecological balance.
Causes/Sources of thermal
Industrial Effluents- Industries require cooling water for heat
removal and cooling purposes. This
heated water when discharged into the
water system increases the temperature
of water body.
Nuclear Power plants-Nuclear power plants emit large quantity of
heat and traces of radioactive
substances which increases the
temperature of water bodies.
Coal- fired power plants- It is one of the major source of thermal
Domestic sewage-When the domestic sewage is disposed off into
water bodies like river, lakes etc it
increases the temperature of receiving
Radioactive waste- Dumping of radioactive waste in marine system
increases the temperature when these
substances radiate energy.
Effects of Thermal
There are two types of effects of thermal pollution
Thermal shock: Due to decrease in DO levels there is suffocation
of plants and animal species which
creates anaerobic conditions .The sudden
change in the temperature causes harm to
the aquatic organisms.
Thermal enrichment: The heated water is used for irrigation
purposes to extend plant growing
seasons. The warmer water also increases
the metabolic rate of aquatic organisms
(which in turn decreases the life
expectancy of these organisms). The
speedy growth is beneficial for