Meghan Hodges
Thermal pollution is the degradation of water quality by any process that changes the ambient water temperature. It is a growing concern, especially with climate change exacerbating water temperature increases from power plants, industry, agriculture, and other human sources. Coal power plants, in particular, have been found to contribute significantly to thermal pollution. This is due to the large amounts of water they withdraw from natural sources for cooling, which is then returned to the environment at higher temperatures, impacting aquatic life and ecosystems.
| Characteristics | Values |
|---|---|
| Definition | Degradation of water quality by any process that changes ambient water temperature |
| Cause | Use of water as a coolant by power plants and industrial manufacturers |
| Effect | Decrease in oxygen supply, changes in ecosystem composition, stress, disease, death |
| Sources | Fossil fuel plants, coal plants, nuclear power plants, biomass, desalination plants, crude oil refineries, steel melting factories, boiler industries |
| Prevention | Switching to clean energy, reducing water released by facilities, capturing heated wastewater |
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What You'll Learn
Water used for cooling machinery
Water is used to cool machinery in coal power plants, which operate at very high temperatures. This water absorbs heat, and the water that does not evaporate is typically discharged back into its source, such as a river, lake, or ocean. This is known as thermal pollution, which is the degradation of water quality by any process that changes the ambient water temperature.
Coal power plants are a significant contributor to thermal pollution. A 2011 report calculated the water used by power plants in each watershed and found that coal plants were responsible for 67% of water withdrawals and 65% of consumption. A 2016 study of the world's rivers found that over 60% of the thermal pollution in the Mississippi River came from coal-fired power plants, and more than 25% was from nuclear plants. The Rhine was another river heavily affected by thermal pollution from power plants.
The Clean Water Act (CWA) requires the EPA to ensure that the location, design, construction, and capacity of cooling water intake structures reflect the best technology available (BTA) for minimizing adverse environmental impacts, including thermal pollution. The EPA has been developing a rule to define how states will establish standards for cooling water intake structures at large power plants.
The water discharged from coal power plants can be up to 20 degrees Celsius warmer than the receiving water bodies, which can be lethal for some species. This heated wastewater decreases oxygen supply and affects the ecosystem composition, harming aquatic plants and animals and causing stress, disease, and even death. Thermal pollution can also reduce the activity of aerobic decomposers, which leads to a decrease in the availability of nutrients in the water bodies.
Switching from fossil fuel plants to clean energy sources like wind and solar power can help reduce thermal pollution, as these plants do not produce heated wastewater or emit greenhouse gases.
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Water used for washing coal
Coal that comes from a mine is a complex mixture of materials with a large variety of physical properties. In addition to the coal itself, pieces of rock, sand, and various minerals are contained in the mixture. Thus, before coal can be sold to consumers, it must be cleaned or washed. The cleaning process consists of a number of steps that result in a product that is specifically suited to the needs of particular consumers. This process is known as coal washing, coal beneficiation, or coal preparation. It is a process used to remove impurities from raw coal before it is burned. This process helps to improve the quality of the coal and reduce environmental impacts when it is used for energy production.
Coal washing improves the coal's energy content, reduces environmental impact, and makes coal more suitable for various industrial applications. The process not only benefits the coal industry but also contributes to cleaner energy production and a more sustainable future. After washing, the clean coal is dewatered and dried before it is ready for use.
The US Department of Energy estimates that the total water used for coal mining in the United States (including water use for coal washing and cooling of drilling equipment) ranges from 70 million to 260 million gallons per day. The water used for coal washing can present a significant hazard if not stored properly. After extraction, coal must be transported to the power plant, and the slurry pipeline method involves pumping water with finely ground coal over long distances.
Coal-fired power plants produce a significant share of US electricity, and they have significant impacts on water quantity and quality. A 2011 report calculated the available water in every major watershed in the US and measured that against the water used by power plants in each watershed. The report found that coal plants were responsible for 67% of water withdrawals and 65% of consumption.
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Heated water returned to the natural environment
Thermal pollution is the degradation of water quality by any process that changes the ambient water temperature. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature, the change in temperature impacts organisms in several ways:
- Firstly, it decreases the oxygen supply in the water. High temperatures deplete oxygen levels, which is essential for aquatic life to thrive. This reduction in oxygen content can disturb the respiratory and digestive rates of aquatic organisms, causing stress and even death.
- Secondly, it affects the ecosystem composition. An abrupt change in water temperature can be lethal for certain species, as most aquatic organisms have developed enzyme systems that operate only within narrow temperature ranges. When a power plant opens or shuts down, the rapid increase or decrease in water temperature, known as "thermal shock", can kill fish and other organisms adapted to a specific temperature range.
- Thirdly, it reduces the activity of aerobic decomposers, which are crucial for breaking down organic matter and maintaining the availability of nutrients in the water bodies.
- Finally, it inhibits the photosynthesis rate of aquatic plants, as the increased temperature hinders enzyme activity. As a result, the diversity and productivity of aquatic plant species decline.
Coal-fired power plants are significant contributors to thermal pollution. A 2011 report found that in 2008, coal plants were responsible for 67% of water withdrawals by water-cooled thermoelectric power plants in the United States. Additionally, a 2016 study revealed that over 60% of the thermal pollution in the Mississippi River came from coal-fired power plants.
To mitigate thermal pollution, existing technologies can be employed, such as reducing water releases and capturing heated wastewater for alternative purposes. Furthermore, transitioning to clean energy sources like wind and solar power can help address the issue, as these renewable energy sources do not produce heated wastewater or emit greenhouse gases.
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Power plants built near bodies of water
Power plants, including coal-fired power plants, are typically built near bodies of water, such as rivers, lakes, or oceans, to utilise water in their operations. Water is used for cooling machinery in power plants, which becomes very hot during operation. The water absorbs heat, and the water that does not evaporate is discharged back into the natural environment.
The use of water as a coolant by power plants is a common cause of thermal pollution. When water used as a coolant is returned to the natural environment at a higher temperature, the change in temperature impacts the aquatic ecosystem. This includes decreasing the oxygen supply and affecting the composition of the ecosystem. Organisms adapted to a particular temperature range can be killed by an abrupt rise in water temperature, known as "thermal shock".
Coal-fired power plants have been identified as significant contributors to thermal pollution. A 2011 report found that coal plants were responsible for 67% of water withdrawals by thermoelectric power plants in the United States. A 2016 study also revealed that over 60% of the thermal pollution in the Mississippi River came from coal-fired power plants.
To mitigate thermal pollution from power plants, various measures can be implemented. These include reducing the amount of water released by power plants and capturing heated wastewater for alternative purposes, such as desalination. Additionally, transitioning to clean energy sources, such as wind and solar power, can help reduce thermal pollution as they do not produce heated wastewater or emit greenhouse gases.
Hydropower plants, which generate electricity from water, are another type of power plant that is often located near bodies of water. These plants use the flow of water to turn turbines and produce electricity. Some hydropower plants use dams to store river water in reservoirs, while others divert a portion of a river through canals or utilise pumped storage systems to generate electricity.
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The use of fossil fuels
Thermal pollution refers to the degradation of water quality caused by changes in ambient water temperature. It is often associated with industrial processes, particularly power generation, that utilise large volumes of water for cooling and subsequently release it back into the environment at higher temperatures. This heated wastewater can originate from various sources within a fossil fuel-based power plant, including the cooling of machinery, boilers, and generators.
Coal-fired power plants, in particular, rely extensively on water for multiple processes. Water is used for washing coal, circulating in boiler furnaces to produce steam, and cooling equipment. The water absorbs heat during these processes, and if it is discharged into nearby rivers, lakes, or oceans without sufficient cooling, it can cause a significant rise in water temperature.
The elevated water temperatures resulting from thermal pollution have detrimental effects on aquatic ecosystems. The sudden change in temperature can lead to a decrease in oxygen supply, disrupting the respiratory and digestive functions of aquatic organisms. It can also affect the reproductive cycles and overall physiological health of various species, leading to stress, disease, and even death. Additionally, the increased temperature inhibits enzyme activity, reducing the photosynthesis rate in aquatic plants and decreasing biodiversity.
The impact of thermal pollution from fossil fuel power plants is not limited to the immediate release of heated wastewater. It also includes the indirect effects on water quality and the surrounding environment. For example, the dust from coal-cleaned water can contaminate groundwater, and the untreated air and water pollutants emitted by these plants can affect the flora and fauna of adjoining areas, rendering them unfit for habitation or livelihood activities.
To mitigate thermal pollution from fossil fuel power plants, several measures can be implemented. These include reducing the amount of water released by such facilities, capturing and utilising heated wastewater for other purposes, and transitioning to cleaner energy sources such as wind and solar power, which do not produce heated wastewater or emit greenhouse gases.
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Frequently asked questions
Thermal pollution is the degradation of water quality by any process that changes the ambient water temperature.
Coal power plants use water for washing coal, circulating in the boiler furnace to produce steam, and cooling equipment. The water absorbs heat, and the water that doesn't evaporate is discharged back into natural bodies of water at a higher temperature, causing thermal pollution.
Thermal pollution harms aquatic life by decreasing oxygen supply and affecting the ecosystem. It can also alter the water chemistry, causing stress, disease, and even death in plants and animals.
Existing technologies can help mitigate thermal pollution, such as reducing the amount of water released by power plants and capturing heated wastewater for other purposes. Additionally, switching to clean energy sources like wind and solar power can help reduce thermal pollution.
