The phenomenon known as thermal pollution may also be classified as a type of water pollution since it is an unfavorable change in the physical, chemical, and biological properties of a natural body of water due to a dramatic shift in temperature within that same body of water.
Whether the temperature of the water rises or falls, the effects are all harmful to the water itself and the organisms within. Particularly when the temperature change happens in a time span much shorter than the natural process would normally allow.
Causes of Thermal Pollution
Thermal pollution often manifests itself following a sudden jump in water temperature due to the waste heat that is a by-product of industrial activity. Bodies of water close to electrical plants that run on coal, oil, or natural gas are the most common examples of thermal pollution caused by heat. Water from nearby lakes and rivers are used as coolant for steam turbines, but once the coolant water has fulfilled its role, it is dumped back into its source. Condensed steam that is a by-product of the cooling process is blended in with the water, making it considerably warmer than before.
There is cause for concern whenever a natural body of water becomes warmer than normal. Warm water reduces oxygen levels. Less oxygen means less chance of survival for fish and other aquatic organisms. These organisms either die of the sudden heat—thus upsetting the food chain—or are forced to relocate to more temperate locations already with established ecosystems and indigenous species. Entering new territory is likely to lead to an ecological imbalance. The few organisms that do survive the heat will instead experience increased metabolism because of the effect of heat on their bodily enzymes. Having to eat more during the same period will ultimately lead to depletions in sources of food, thus also causing these organisms to either die out or relocate.
Thermal pollution may also be caused by exposure to water of lower temperature, though this does not happen as often. The most common example of this is the release of relatively cold water from man-made depositories such as reservoirs into nearby rivers and lakes where the water is naturally warm. As is the case with heat, most aquatic organisms that have been thriving in warm water for their entire existence will not last even half a day in lower temperatures.
Like any other form of pollution, thermal pollution causes problems for the environment that require immediate solutions, some of which have already been adopted by the same entities whose activities actually contributed to the pollution. Many power plants and industrial facilities now make use of in-house facilities such as man-made cooling ponds that regulate the temperature of water before it is discharged and cooling towers that convert heat waste into gas and release it into the atmosphere after its harmful effects have been all but neutralized. There is still no documented solution to thermal pollution caused by cold water although this doesn’t necessarily mean that there isn’t one already in development or discovered.