When the heat released into the water or air produces some undesirable effects and it increases the environment temperature, this is known as thermal pollution. Some of the reasons of thermal pollution are volcanoes, forest fires, thermal power plants etc.
Sources of thermal pollution:
Thermal power plants: Thermal power use coal as a fuel. These power plants are major source of thermal pollution.
Industrial effluents: Some of the industries use water to remove the heat. Therefore heat is transferred to water. Example power plants, textile and sugar industry etc.
Nuclear power plants: Emission from nuclear reactors is responsible for increasing the temperature of water bodies.
Domestic sewage: Domestic sewage, without treatment, discharged into the rivers and canals has higher temperature than receiving water. This increases the temperature of water bodies.
Control of thermal pollution:
The thermal pollution adversely affects the aquatic ecosystem so it is necessary to control the thermal pollution. The various methods used to control the pollution are
Cooling ponds: Cooling ponds maximize the heat dissipation to the atmosphere and minimize the water area.
Cooling towers: The cooling towers works on the principle of evaporation. It cools the working water near to the wet bulb air temperature.
Effects of thermal pollution:
The heated water added to the water bodies increases the temperature of water bodies. This added heat affects the concentration of dissolved oxygen. It also disturbs the life of species like fish.