Thermal Pollution | Causes And Consequences

Thermal pollution is defined as a human-caused change in the temperature of a natural body of water, such as an ocean, lake, river, or pond.  When a plant or facility takes water from a natural resource and returns it at a different temperature, this is what happens. Typically, these facilities use it to cool their machinery or to aid in the production of their products.
  • The term "thermal pollution" refers to an increase in the optimum water temperature caused by industrial processes (steel factories, electric power plants, and atomic power plants). 
  • Many industries generate their electricity and cool their generators with water.
  • This hot water is released back into the system from which it was drawn, causing surface water to warm. 
  • If the system is not properly flushed, the temperature may rise permanently. If the water is released into the well-flushed system, however, there is no permanent increase in temperature.


1.    Water as a Coolant in Power, Manufacturing, and Industrial Facilities:

  • The largest source of thermal pollution is manufacturing and production plants. 
  • These plants draw water from a nearby source to keep machines cool, then release it at a higher temperature back to the source.
  • The water temperature rises dramatically when heated water returns to the river or ocean. 
  • When oxygen levels in the water are altered, it can affect the quality and longevity of life in underwater wildlife. This process can also obliterate streamside vegetation, which is reliant on constant oxygen and temperature levels. 
  • Industries are essentially lowering the quality of life for these marine-based life forms by altering natural environments, and if their practices are not controlled and careful, they can eventually destroy habitats.

2.     Soil Erosion: 

  • Another major cause of thermal pollution is soil erosion.
  • Water bodies rise as a result of constant soil erosion, exposing them to more sunlight. 
  • The high temperature may cause anaerobic conditions in aquatic biomes, which could be fatal.

3.     Deforestation: 

  • Trees and plants block sunlight from reaching lakes, ponds, and rivers directly.
  • When forests are cut down, these water bodies are exposed to direct sunlight, absorbing more heat and raising their temperature. 
  • Deforestation is also a major contributor to higher levels of greenhouse gases in the atmosphere, resulting in global warming.

4.     Runoff from Paved Surfaces: 

  • Urban runoff from paved surfaces such as roads and parking lots can heat surface waters.
  • During the summer, the pavement becomes quite hot, resulting in warm runoff that enters sewer systems and water bodies.

5.    Natural Causes:

  • Volcanoes and geothermal activity beneath the oceans and seas can cause warm lava to rise in temperature, raising the temperature of water bodies. 
  • Lightning can also cause massive amounts of heat to be released into the oceans. This means that the water source's overall temperature will rise, having significant environmental consequences.


  • When it comes to the effects of thermal pollution, there are generally two schools of thought among recognized scientists and scholars.
  • Some argue about the negative effects of pollution on marine ecosystems and how it undermines good environmental practices. 
  • However, some argue that if these industries did not function as they do, some of the most basic aspects of human life would be rendered obsolete.
  • We wouldn't be able to properly maintain wastewater, we wouldn't have any industries capable of producing the goods we require, and so on. 
  • However, the negative effects of thermal pollution on ecosystems far outweigh the benefits that industries gain from participating in the practice.
1. Reduced levels of DO (Dissolved Oxygen): The amount of DO (Dissolved Oxygen) in water decreases as the temperature rises. Warm water has a lower oxygen content than cold water. Reduced oxygen levels can cause suffocation in plants and animals such as fish, amphibians, and copepods, resulting in anaerobic conditions. Warmer water encourages algae growth on the water's surface, which can reduce oxygen levels in the water over time.
2. Increase in Toxins: Due to the constant flow of high-temperature discharge from industries, toxins are being regurgitated into natural bodies of water at an alarming rate. These toxins could contain chemicals or radiation that hurt the local ecology and make people more susceptible to disease.
3. Biodiversity Loss: A decrease in biological activity in the water could result in a significant loss of biodiversity. Changes in the environment may cause certain species of organisms to relocate, while a large number of species may migrate in due to warmer waters. Organisms that can easily adapt to warmer temperatures may have an advantage over organisms that aren't used to them.
4. Ecological Impact: A sudden temperature change can kill a lot of fish, insects, plants, and amphibians. Hotter water may be beneficial to some species, but it could be fatal to others. The level of activity increases as the water temperature drops, and the level of activity decreases as the water temperature rises. Small temperature changes, such as one degree Celsius, can cause significant changes in organism metabolism and other detrimental cellular biology effects in many aquatic species.
5. Affects Reproductive Systems: Increasing temperatures can cause a significant halt in the reproduction of marine wildlife (although reproduction can still occur between fish – the likelihood of defects in newborns is significantly higher) because reproduction can only occur within a certain temperature range. Excessive heat can cause immature eggs to be released or prevent certain eggs from developing normally.
6. Increases Metabolic Rate: Thermal pollution causes an increase in enzyme activity in organisms, causing them to consume more food than they would normally require if their environment remained unchanged. It disrupts the food chain's stability and changes the composition of species.
7. Migration: Warm water can cause certain species of organisms to migrate to a more suitable environment that meets their survival needs. As a result, those species that rely on them for their daily food may suffer as their food chain is disrupted.
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Thermal pollution must be controlled because its negative effects on aquatic ecosystems may be detrimental in the future.
The following are viable solutions to chronic thermal discharge into water bodies:

1.    Cooling Ponds:

  • The most basic method of controlling thermal discharges is to use cooling ponds or reservoirs.
  • In cooling ponds, heated effluents on the surface of the water maximize heat dissipation to the atmosphere while reducing water area and volume. 
  • This is the simplest and most affordable method for cooling water to a very low temperature. However, in terms of air-water contact, the technique alone is less desirable and inefficient

2.    Cooling Towers: 

  • The cooling process is defined as the use of water from water sources for cooling purposes, with the water being returned to the water body after passing through the condenser. 
  • Cooling towers are designed to control the temperature of water to improve the cooling process. Cooling towers are used to dissipate the recovered waste heat, thereby preventing thermal pollution.

3.     Artificial Lake: 

  • Artificial lakes are man-made bodies of water that can be used as a cooling alternative to natural lakes. 
  • At one end, heated effluents can be discharged into the lake, while water for cooling can be withdrawn from the other. Through evaporation, the heat is eventually dissipated.
  • These lakes must be replenished regularly. Several methods for converting thermal effluents from power plants into useful heat resources have been proposed and developed to maximize the benefits.

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