Thermal pollution, or thermal enrichment as it is also known, refers to an abnormal rise or fall of the temperature of a natural water body due to human influence.Water bodies such as rivers and large lakes suffer the most with the wrath of thermal pollution, a sudden change in the water temperature of a pond or lake can upset its aquatic life massively. At first instance, people do not realize the magnitude of the term ’thermal pollution’, people have a notion of referring to carbon emissions or personal waste when hearing the term pollution.Upsettingly, thermal pollution is equally dangerous for the environment, it is linked with water pollution to some extent as it is the release of coolant water from power plants and other factories which causes thermal pollution. Some people at times mistake thermal pollution for chemical pollution, but both of them are entirely different. The former leads to a change in the physical properties of water, troubling the aquatic organisms whereas chemical pollution can make the water body poisonous, completely inhabitable. Apart from a power plant or some other industrial plant, even dam reservoirs contribute to thermal pollution. When dams release water present in the base of the reservoir during the summer days, the water temperature is around 50 °F (10 °C) cooler than the water temperature at the top. As the water is released into a natural waterbody, it leads to a sudden drop in the average water temperatures. Aquatic animals who are adapted to living at elevated temperatures can go into a thermal shock which can affect their health. On a large scale, thermal pollution is really bad and its effects are devastating for various fish species.Causes And Effects Of Thermal PollutionYou can observe thermal pollution as soon as the aquatic species go into a thermal shock owing to a sudden change in the average temperature range of the water body. It is usually seen that when water temperatures rise significantly there is greater harm on the aquatic animals. The heat of the water which mixes with the lake or the river degrades the water quality of the natural water body and has an impact on aquatic life.Industrial wastewater generated by power plants, paper mills, chemical plants, smelters, steel mills and petroleum refineries is the leading cause of thermal pollution. Perhaps to your surprise, there do exist multiple methods to control the direct discharge of the heated water into a natural body of water. Under these methods, the waste heat can in fact be recycled for domestic heating uses but companies do not resort to these methods. Instead, the power plants in particular and all the other contributing industries, in general, undertake the system of Once-Through Cooling (OTC). This system does not remove the excess heat of water when discharged and the water is directly discharged into a river or lake at a higher temperature than recommended. On average, a power plant takes around 500 million gal (22.73 million l) of water a day for cooling purposes, they use cool water in the OTC system but produce water at warmer temperatures, around 50 °F (10 °C) higher. When this warm water is released into the natural environment, it can harm fishes and other aquatic animals who aren’t capable of surviving at a high temperature. Urban runoff is another leading cause of thermal pollution even though it doesn’t harm as much as the warm water released from power plants. Urban runoff takes place when stormwater goes directly into the natural water bodies after passing through hot rooftops, sidewalks, parking lots. When the water passes through any of these areas, it becomes relatively hot and as the warmer water now mixes with the natural river water, it does some damage to marine life. There are several natural causes too that lead to thermal pollution such as lightning strikes in sea or ocean water, lava from volcanoes and several other geothermal features. The effects of thermal pollution in such water bodies are quite dangerous, a rise in the temperature of these water bodies leads to a fall in the oxygen levels of the water body as gases aren’t soluble in hotter liquids. An increase in the rate of metabolism is another effect of thermal pollution in aquatic animals which can lead to scarcity of resources thus resulting in the entire food chain. Some of the other effects include failure to reproduce, disruption in the balance of microbial growth, malnutrition, elimination of native fish species.Thermal Pollution And The EnvironmentJust like air pollution, water pollution, soil pollution, radioactive pollution thermal pollution also affects the environment in a negative manner. The discharge of heated water or excessively cold water into a natural water body leads to thermal pollution, the sudden change in the ambient temperature level of the waterbody leads the aquatic organisms into a thermal shock disrupting their life balance.Thermal pollution can be seen directly affecting the environment by only disrupting the life of the aquatic organisms that live in that particular lake or river but in reality, the chain reactions that take place affect the entire environment in multiple areas. Studies have shown that thermal pollution can lead to an increase in surface temperatures during the summer season. It then affects the water temperature which further leads to the release of warm air into the atmosphere and eventually increases the air temperature. In the long shot, thermal pollution is also a contributor to global warming as bizarre as that sounds, if power plants continue the discharge of water without running them through cooling ponds or cooling towers, in the long run, the effects can be devastating. Another problem that has been created due to thermal pollution and leads to more thermal pollution is seen in various rivers including the Mississippi. What happens is a power plant situated upstream of a river releases water of comparatively warmer temperature into the river after it has used it as a coolant. As this water now flows downstream and is used by the other power plants, they receive relatively warm water due to which their intake of water increases for cooling purposes. As these power plants take in more cooling water for their plant, they also release a great amount of water of high temperature which does nothing but increase the magnitude of thermal pollution in the river. This cycle keeps on increasing the average temperature of the river’s water and depleting oxygen levels. Thermal pollution also changes the health condition of fishes and other aquatic animals, some of them can then become hazardous to consume. If we humans then eat those fishes, they can have an effect on our health as well.Prevention Of Thermal PollutionUnlike other types of pollution such as air pollution, soil pollution and water pollution which will take some time to get control on, thermal pollution can be stopped immediately if the power plants act effectively on the pollution control methods. The cold water which power plants require for the cooling process can be returned back to the natural water source with no rise in temperature if the power plants can undertake the pollution control mechanisms.Currently, there are three methods using which power plants can cut down their emission of thermal energy as waste, these three methods include cooling ponds, cooling towers and cogeneration. Either of these methods can be undertaken to reduce thermal pollution and bring back the balance in marine life. A cooling pond refers to a man-made water body that is used to store cooling water as well as to cool the heated water. A cooling pond undertakes methods like evaporation, convection and radiation to cool down the heated water so that it can once again be used, the water which is lost in evaporation is added back. Studies have shown that cooling ponds are cheaper than cooling towers but take more space for their construction. Cooling towers, on the other hand, are devices that reject waste heat to the atmosphere by cooling a coolant stream to a lower temperature. They were first originated in the 1800s and can be seen in chemical plants, oil refineries, nuclear power stations, thermal power stations and petrochemical plants. Cogeneration or as it is also known as, combined heat and power (CHP) refers to the use of a heat engine to recycle the otherwise wasted heat energy for industrial or domestic heating purposes. Cogeneration is in fact the most efficient method of utilizing the heat energy present in the used cooling water.Harmful Effects Of Thermal PollutionThermal pollution from chemical plants, nuclear power plants and all other industrial sources has a devastating effect on the environment. In brief, thermal pollution can completely damage the water ecosystem of the river or lake it drains in. It can reduce the growth of marine animals and on the contrary lead to an increase in the presence of algae and bacteria, let us take a look at these harmful effects in some more depth.Different organisms react to temperature change in different ways, usually, multicellular organisms and plants tend to be harmed by the change but bacteria and algae tend to benefit from it. The most harmful effect of thermal pollution is the reduction of oxygen levels in water due to a rise in temperature. Decreased oxygen levels lead to dispersion of aquatic animals affecting the wildlife of that area and also causing an algae bloom. An increase in algae in the water is a potential life threat to both aquatic plants and animals. Migration and dispersion of aquatic animals to areas where there is low pollution can disrupt the biodiversity of a place and also its food chain. Along with thermal pollution caused by power plants, it is often seen that plants also release chemical wastes and nuclear power plants at times radioactive cooling water as well. All these toxic elements can be pretty devastating for marine life as they can lead to gene mutations and at times fatal poisoning. In some cases, it has been noted that thermal shock and the presence of toxic elements in water have led to reproductive issues in marine animals which can again disrupt the ecosystem of the waterbody and eventually the entire food chain.
Thermal pollution, or thermal enrichment as it is also known, refers to an abnormal rise or fall of the temperature of a natural water body due to human influence.
