E.6. Thermal Pollution
Thermal pollution involves changes in the temperature of natural water bodies—either a rise or drop—resulting from human activities. It has become an increasingly pressing environmental issue, largely fueled by the expansive reach of globalization.
This type of pollution typically occurs when industries and power plants discharge heated water into rivers and lakes, or when vegetation along waterways is removed, exposing them to direct sunlight and raising their temperature. In some cases, the release of unusually cold water can also disrupt the natural thermal balance.
Much like other forms of water contamination, thermal pollution doesn’t remain confined—it spreads, affecting countless aquatic ecosystems in lakes, rivers, and other water bodies across the globe.
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Major sources
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- Power plants generating electricity from fossil fuels utilize water as a cooling agent in industrial facilities, contributing to shoreline deforestation and soil erosion.
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Ecological Effects — Warm Water
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- Temperature changes impact organisms by decreasing oxygen supply and affecting ecosystem composition.
- Warm water, with reduced oxygen levels, alters the decomposition of organic matter and may lead to the dominance of less desirable blue-green algae.
- Increased metabolic rates in aquatic animals result in higher food consumption, potentially causing food source shortages and population decreases.
- Environmental changes may prompt organism migration and competition for resources, compromising food chains and reducing biodiversity.
- Even slight temperature changes can adversely affect organism metabolism and cellular biology.
- Warm water can affect plant growth, leading to species overpopulation, algae blooms, reduced oxygen levels, and nutrient enrichment similar to eutrophication.
- Higher temperatures can denature enzymes, impacting aquatic organisms’ ability to break down lipids and causing malnutrition.
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Ecological Effects — Cold Water
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- Thermal pollution can occur when very cold water is released from reservoirs into warmer rivers, affecting fish, macroinvertebrates, and river productivity.
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Control Measures
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- Instead of discharging heated water directly into lakes and streams, power plants and factories can pass it through cooling towers or ponds for evaporation cooling.
- Power plants can be designed or retrofitted for efficiency to minimize waste heat production.
- Cogeneration involves using excess heat energy from electricity generation in other manufacturing processes or for heating in nearby buildings.
- To prevent thermal pollution due to devegetation, it is advised to maintain vegetation along streams and shorelines.
- Efforts to control erosion also contribute to water clarity, helping to mitigate thermal pollution.
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