What is Thermal pollution?
Thermal pollution is any deviation from the natural temperature in habitat and can range from elevated temperatures associated with industrial cooling activities to discharges of cold water into streams below large impoundments.
Thermal pollution, sometimes called “thermal enrichment,” is the degradation of water quality by any process that changes ambient water temperature. Thermal pollution is a sudden increase or decrease in temperature of a natural body of water, which may be ocean, lake, river, or pond by human influence.
Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers.
Urban runoff stormwater discharged to surface waters from rooftops, roads and parking lots and reservoirs can also be a source of thermal pollution. Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers.
When the water used as a coolant is returned to the natural environment at a higher temperature, the sudden change in temperature decreases oxygen supply and affects ecosystem composition. Fish and other organisms adapted to a particular temperature range can be killed by an abrupt change in water temperature known as “thermal shock”.
Causes of Thermal pollution
1. Water as a Cooling Agent in Power, Manufacturing and Industrial Plants
Production and Manufacturing facilities are the largest sources of thermal pollution. These plants draw water from a nearby source to keep the machines cool and then return it to the source at higher temperatures. When heated water returns to the river or ocean, the water temperature rises sharply.
When the oxygen levels in the water change, it can also affect the quality and longevity of underwater wildlife. This process can also wipe away the vegetation on the river, which is constantly dependent on constant levels of oxygen and temperature.
2. Soil Erosion
Soil erosion is another important factor that leads to thermal pollution. Due to the ongoing soil erosion, the waters rise and are more exposed to sunlight. The high temperature could prove fatal to aquatic biomes as it can lead to anaerobic conditions.
Trees and plants prevent sunlight from falling directly onto lakes, ponds or rivers. With deforestation, these bodies of water are exposed directly to sunlight, absorb more heat and increase temperature.
Deforestation is also the main cause of the higher concentrations of greenhouse gases, i.e. Global warming in the atmosphere.
4. Runoff From Paved Surfaces
Urban runoffs discharged into surface water from paved surfaces such as streets and parking lots can make the water warmer. During the summer season, the pavement gets quite hot, creating warm drains that enter sewers and bodies of water.
5. Natural Causes
Natural causes such as volcanoes, geothermal springs, and hot springs under the oceans and seas can trigger warm lava to raise the temperature of the waters. Lightning can also add a large amount of heat to the oceans.
This means that the overall temperature of the water source increases and has a significant impact on the environment.
6. Retention Ponds
Retention Ponds can be another source of thermal shock as the relatively small and shallow bodies of water can absorb some of the thermal energy from the sun.
If this water is pumped directly into a river, lake, or cove, it will cause a significant increase in temperature. It’s similar to pouring a hot pitcher of water into a bathtub full of water, causing the water to bounce a few degrees Fahrenheit.
7. Domestic Sewage
Domestic wastewater is often discharged into rivers, lakes, canals or streams without treating the waste. The temperature of municipal wastewater is usually higher than that of the receiving water.
As the temperature of the absorbing water increases, the dissolved oxygen (DO) decreases and the oxygen demand increases, which leads to anaerobic conditions.
Effects of Thermal pollution
The effects of thermal pollution include decreasing the amount of dissolved oxygen in the water, which aquatic life requires, damage to larvae and eggs of fish in rivers, killing off some species of fish and macroinvertebrates that have limited tolerance for temperature change, and migration of living entities from their environment.
The effects of thermal pollution are diverse, but in short, thermal pollution damages water ecosystems and reduces animal populations:
1. Decreased Dissolved Oxygen
Warm water contains less oxygen than cold water. When oxygen levels drop, animals that cannot move to another area can begin to die. In deeper waters, injecting warm water can prevent oxygen from dispersing in deep water. This may be good for bacteria, but dangerous for aquatic animals.
Fish and amphibians can move away from the warm water to a more suitable location and disrupt the ecosystem for remaining animals. Birds may also be forced to go in search of areas with more food. Plants and certain animals get stuck in the area, which can lead to enormous losses.
3. Increased Toxins
Toxins in water are more of a side effect of sanitation than a direct effect of thermal pollution. Chemical pollution is an almost inevitable side effect of using water for cooling. Solvents, heating oil, and dissolved heavy metals end up in the lake or river, where the cooling water is drained off.
4. Loss of Biodiversity
Sudden warming can kill or drive off endangered organisms. This is one of many serious problems for threatened and endangered species. This loss can be caused by organisms dying from the hot water, unable to reproduce as effectively as before, or simply leaving the area.
5. Ecological Impacts
The local aquatic ecosystem can be damaged by thermal pollution, especially when it is dramatic, such as when copious amounts of warm water are channeled into a cool pond, cove, or river. “Thermal shock” can kill insects, fish, and amphibians.
This sudden loss of life creates further problems with the ecosystem. Important food sources are no longer sufficient.
6. Reproductive Effects
A significant increase in temperature in the water can lead to reproductive problems. Warmer water can affect the fertility of some organisms. Other species may experience birth defects or lay deformed eggs due to chemical changes in the body caused by warmer water.
Defective eggs and birth defects affect the general fertility of the animal population and can reduce the population.
7. Increased Metabolic Rate
Warmer water can be good for cold-blooded fish and amphibians, but only for a limited time. One of the many real problems warm water can cause is faster metabolism, which means animals need more food.
The local ecosystem may not be able to support a significant increase in food consumption. Worse still, the warmer water gives certain organisms an advantage while it harms others.
How can thermal pollution be prevented?
The following measures can be taken to prevent or control high temperature caused by thermal pollution:
- Heated water from the industries can treated before discharging directly to the water bodies.
- Heated water from the industries can be treated by the installation of cooling ponds and cooling towers.
- Industrial treated water can be recycled for domestic use or industrial heating.
- Through artificial lakes: In this lake Industries can discharge their used or heated water at one end and water for cooling purposes may be withdrawn from the other end. The heat is eventually dissipated through evaporation.
Hence, we can say any kind of pollution may directly or indirectly affect humans because the loss of biodiversity causes changes that affect all aspects of the environment.