Since 1880, the power plants and industries have resulted in thermal pollution, equivalent to 0.02 W m^-2 global warming today. So far, this warming has resulted in a 0.7°C increase in global temperature. Thermal pollution is the degradation of water quality caused by any process that alters the temperature of the surrounding water. Organisms that are unable to adapt may die from a variety of causes or be compelled to leave the area, upsetting the ecosystem. Thermal Pollution can be controlled by appropriate pollution control measures like the construction of artificial lakes, cooling ponds, and cooling towers and by employing the cogeneration process, shifting away from once-through cooling systems. This article will explain to you about Thermal Pollution which will be helpful in preparing the Environment syllabus for the UPSC Civil Service exam.

Thermal Pollution - Concept

• The rise or fall in temperature of a natural aquatic environment induced by human intervention is known as thermal pollution.
• This has become increasingly common due to the expanding demand for globalization everywhere.
• Thermal pollution is generated by dumping hot water from factories and power plants, or by removing trees and vegetation that shade streams, allowing sunshine to raise the temperature of these waters, and then releasing cold water to cool them down.
• Thermal pollution, like other types of water pollution, is ubiquitous, impacting numerous lakes and a large number of streams and rivers around the world.

Examples of Thermal Pollution

• The Mississippi River ranked first in a global study of thermal pollution in rivers published in 2016.
• Coal-fired power facilities accounted for 62% of the river's heat emissions, while nuclear power generation accounted for 28%.
• Other thermal pollution sources include agricultural runoff and wastewater.
• Europe's Rhine River also suffered significant impacts from power plant emissions, most notably from nuclear plants.
• Water-scarce countries, particularly in the Middle East, have turned to desalination as a means of bolstering water security in the face of drought and climate change.
• The mixing of cooling water to dilute salty wastewater caused a heated plume 25 percent warmer than natural seawater temperature, putting stress on local benthic creatures along the bottom, according to a 2020 study of desalination plants in Ashkelon and Hadera along Israel's Mediterranean coast.

Sources of Thermal Pollution

Power Plants

• Thermal pollution is caused by thermoelectric power stations that use coal, natural gas, nuclear power, biomass, and other waste products as fuel.
• Typically, power plants are situated next to a river, lake, or ocean, which provides a constant supply of water.
• This is transformed into steam, which is used to power turbines, which generate electricity.
• Water is also utilized to keep machinery cool when it gets too hot. The water absorbs heat and is normally released back to its source if it does not evaporate.
• This ultimately results in a rise in the temperature of water bodies and causes thermal pollution.

Industrial Wastewater

• Industrial plants, such as petroleum refineries, pulp, and paper mills, chemical plants, and steel mills, contribute to thermal pollution, in addition to power plants.
• Water is also used to cool machinery and to discharge water at high temperatures.
• Once-through cooling is the process of draining water from a lake, ocean, or river for industrial uses and then releasing hot water back to its source. It is one of the most significant contributors to thermal pollution.
• It has long been recognized as having a negative impact on aquatic and marine habitats.
• Fish and larvae stuck against intake screens are killed by once-through cooling, and habitats are altered by the release of warmer, frequently dirty water.

Desalination Plants

• Once-through cooling is also used in desalination plants.
• More than half of the desalinated seawater is discharged into the ocean as effluent, frequently at a high temperature.
• Desalination plants are crowded together in several parts of the world, discharging huge amounts of hot, saline wastewater into shallow coastal locations.
• This can drastically increase the warmth and salinity of saltwater.

Urban Runoff

• Urban runoff can have a considerable thermal impact on minor waterways during hot weather.
• Surface runoff absorbs some of the heat as it travels over hot rooftops, parking lots, roadways, and walkways, creating an urban heat island effect.
• The runoff water management facilities, such as bioretention systems and infiltration basins, which absorb runoff or route it into groundwater, lessen these thermal impacts by giving the water more time to discharge excess heat before entering the aquatic environment.
• These linked runoff management technologies are part of a growing urban design strategy known as green infrastructure.
• Because the water may be heated by the sun before being discharged to a receiving stream, retention basins (stormwater ponds) are less effective at reducing runoff temperature.

*To know more about the topic, click this link Sources of Thermal Pollution

Effects of Thermal Pollution

Decrease in DO (Dissolved Oxygen) Levels

• The amount of DO (Dissolved Oxygen) in water decreases as the temperature rises.
• Warm water has a lower oxygen content than cold water.
• Reduced DO can cause suffocation in plants and animals like fish, amphibians, and copepods, resulting in anaerobic conditions.
• Animals that are unable to relocate to another place may begin to die if the oxygen level falls.
• Warm water injections into deeper bodies of water can prevent oxygen from diffusing, which is beneficial to bacteria but harmful to aquatic species.
• Algal blooms can result from a lack of oxygen, posing harm to aquatic plants and animals. It is one of the most common and well-known negative effects of thermal pollution is algal blooms.

An Increase in Toxins

• Toxins in the water are a result of dumping wastewater rather than being a direct result of thermal pollution.
• The toxins include heavy metals such as arsenic, mercury, cadmium, chromium, lead, and more.
• The use of water for cooling almost always results in chemical contamination.
• Solvents, fuel oil, and dissolved heavy metals end up in the lake or river where cooling water is discharged.
• Cooling water from nuclear power plants can be mildly radioactive.
• The compounds could have a wide range of adverse consequences on plants and animals, including death, mutations, and sterilization.

Loss of Biodiversity

• The sudden rise in temperature might kill or drive away vulnerable organisms.
• For fragile and endangered animal species, this is just one of many critical challenges.
• Organisms suffering from the hot water, being unable to reproduce as effectively as before, or simply abandoning the area can all contribute to this loss.
• Animals are frequently the victims of water pollution, but multicellular aquatic plants are also at risk when the local aquatic ecology is altered by thermal pollution.

Ecological Impact

• Thermal pollution can harm the local aquatic ecosystem, especially if it is severe, such as when large amounts of warm water are poured into a frigid pond, bay, or river.
• The fast shift in water temperature, either an increase or reduction, known as thermal shock, can kill fish and other creatures that evolved to a specific temperature range when a power plant first opens or shuts down for repair or other reasons.
• This untimely death has exacerbated the ecosystem's problems. The availability of key food sources has dwindled.
• A local population that is threatened or endangered may be wiped out or put under even more stress.
• When waste from a power plant or business is thrown into coastal waters, coral reef bleaching can occur. When coral organisms die, coral bleaching occurs.

*To know more about the topic, click this link Effects of Thermal Pollution

Measures to Control Thermal Pollution

Cooling Ponds

• The most basic ways of controlling thermal discharges are cooling ponds or reservoirs.
• Heated effluents on the surface of the water in cooling ponds maximize heat dissipation to the atmosphere while reducing the area and volume of water.
• This is the simplest and most affordable way to chill the water to a very low temperature.
• However, in terms of air-water contact, the method alone is less attractive and inefficient.

Cooling Towers

• The cooling process is defined as the process of taking water from water sources for cooling purposes and then returning it to the water body after passing through the condenser.
• As a result, cooling towers are built to regulate the temperature of water in order to improve the cooling process.
• Cooling towers are primarily used to dissipate recovered waste heat and hence alleviate thermal pollution issues.

Artificial Lakes

• Artificial lakes are man-made bodies of water that can be used as an alternative.
• It can be created by damming a valley, digging the land, or enclosing an area of land with dykes and redirecting a portion of the river flow into the reservoir.
• The heated effluents could be dumped into the lake on one end, and the water could be recovered for cooling on the other.
• Through evaporation, the heat is gradually released. However, these lakes must be replenished on a regular basis.

Spray Ponds

• A spray pond is a reservoir where overheated water from a power plant is cooled before reuse by spraying it into the cooler air via nozzles.
• Cooling is accomplished through heat exchange with the surrounding air.
• This includes both conductive heat transfer between the water droplets and the surrounding air as well as evaporative cooling which provides by far the greatest portion, typically 85 to 90 percent, of the total cooling.
• This eventually aids in controlling thermal pollution.

*To know more about the topic, click this link Measures to Control Thermal Pollution

Conclusion

River temperature fluctuations are a natural occurrence, and the ecology is generally resistant to natural changes. However, damming those natural river systems extensively as a result of thermal pollution has resulted in not only a net shift in temperature profiles but also a homogenization of those temperatures over extended time periods. Negative biological responses are triggered by such homogenization changes. Thus, appropriate measures must be taken to control this type of pollution. However, scientists and researchers are striving to establish a framework that can forecast changes in thermal regimes defined across a wide temperature range rather than precise temperature changes.

FAQs

MCQs

1. Which of the following is a primary source of thermal pollution?

A) Agriculture
B) Power Plants
C) Residential Areas
D) Mining

2. Thermal pollution primarily affects:

A) Aquatic ecosystems
B) Urban temperature
C) Air quality
D) Soil fertility

3. Which measure helps control thermal pollution?

A) Desalination
B) Cooling Towers
C) Mining
D) Deforestation

4. Thermal pollution decreases the levels of:

A) Water temperature
B) Dissolved Oxygen
C) CO2 concentration
D) Nutrients

5. The term "thermal shock" refers to:

A) Sudden water cooling
B) Sudden water heating
C) Rapid temperature change
D) None of the above

GS Mains Questions and Model Answers

Q1: Discuss the impact of thermal pollution on aquatic ecosystems. What steps can industries take to mitigate its effects?

Answer: Thermal pollution raises water temperatures, disrupting aquatic life by lowering dissolved oxygen and causing thermal shock. It leads to biodiversity loss as sensitive species die or migrate. Industries can install cooling towers, artificial lakes, and closed-loop systems to cool water before discharge, thereby reducing thermal pollution.

Q2: Analyze the role of thermal pollution in the depletion of biodiversity in freshwater ecosystems. Provide examples.

Answer: Thermal pollution alters habitats by increasing water temperature, which affects oxygen levels. Species that cannot adapt face mortality or relocation. Examples include fish kills in rivers near power plants. Efforts like regulated discharge temperatures and cooling ponds are needed to preserve biodiversity.

Q3: Examine the causes of thermal pollution and suggest policy measures to manage its impact on the environment.

Answer: Thermal pollution arises from industrial discharge of heated water and urban runoff. It depletes dissolved oxygen, harming aquatic life. Policies should enforce temperature regulation, promote closed-loop systems, and mandate eco-friendly cooling methods to manage environmental impact effectively.

Previous Year Questions on Thermal Pollution

1. UPSC CSE Prelims 2021:

Question: Which of the following industries is a major contributor to thermal pollution?

A) Power Plants
B) Agriculture
C) Forestry
D) Textiles

Answer: (A)

Explanation: Power plants are primary contributors to thermal pollution by releasing heated water back into natural sources without adequate cooling.

2. UPSC CSE Mains 2019 (GS Paper 3):

Question: "Explain the concept of thermal pollution. What steps can be taken to address the adverse impacts of thermal pollution on water bodies?"

Answer: Thermal pollution is the release of excess heat into water bodies from industrial and urban sources, disrupting aquatic life. Solutions include cooling towers, artificial lakes, and regulations on discharge temperature to minimize ecological damage.