Thermal Pollution: Understanding the Causes and Effects of this Environmental Threat

Chemical pollution, light pollution, and noise pollution are all part of the habited landscape. Thermal pollution is another form of contamination that is less well-known, but has far-reaching effects. 

When bodies of water change in temperature dramatically, all the organisms dependent on that water source are affected. Ultimately, this has consequences for humans. 

We'll cover the key contributors to thermal pollution, how it affects human water use, and what we can do to ensure a clear, reliable water source. 

Source:  Rahul Pabolu on Unsplash

What is thermal pollution and why should we be concerned?

This concept isn't widely discussed, unless you work in industrial or water management careers. 

Thermal Pollution: The abrupt change in water temperature — either through an increase in cold OR heat - that can cause dramatic shifts in chemical composition and ecology.

So, this kind of pollution has to do with radial changes in the amount of hot and cold water flowing through a system. 

The importance of Water Temperature in Ecosystems

Temperature is a crucial component of any habitat. The ambient water temperature determines, in part, what organisms can live there. 

For example, increases in water temperature can provoke rapid growth of algae. These are called algal blooms. Not only are they unsightly, but they quickly consume the oxygen in a water source, like a river. This kills off the fish and other oxygen-hungry organisms living in the water. 

WATCH NOW: 7 Harmful Effects of Thermal Pollution 

How Thermal Pollution Differs from Other Forms of Water Pollution

We're familiar with pollution in the form of plastic bags, bottles, chemicals, and oil spills. These kinds of contamination can damage the drinking water supply and harm the ecosystem.

Thermal pollution affects the water supply slightly differently than these other forms of pollution, because it changes the chemical composition of the water itself. Gasses - like oxygen - don't dissolve as easily in warm water. The level of dissolved oxygen is crucial for many lifeforms to survive. This means that the ecological effects of thermal pollution come from the change in the water. 

The end result of all these kinds of pollution is similar. Dangerous drinking water for humans, fewer fish and other edible aquatic life, and dangerous compounds in the water that can actually become poisoning.

Source: Jordan Whitfield on Unsplash

What are the main causes of thermal pollution?

Most thermal pollution comes from dumping headed water into oceans, lakes, and rivers. This is done as part of the power generation process. It also happens as part of manufacturing. 

Power plants as a major source of thermal pollution

Water is used to generate electricity in two different ways: 

Hydroelectric Power: Sometimes, the flow of water is used to directly spin turbines. These turn the generator, which produces electricity. 

Coolant for Coal-Generated Electricity: Other power plants use water for cooling. Water can also be boiled to produce steam, which is called thermoelectric power. 

Currently, about 65% of the United States' energy supply comes from power generation sources that require cooling. 

This means that power generation is a major source of thermal pollution — and we know it's changing the composition of our country's water supply. 

Industrial processes and their contribution to heated water discharge

Another major source of thermal discharges into our water supply is through industrial sources.

Most of us have poured water over a campfire to cool it down. Thanks to the principle of heat transfer, introducing cooler water is an easy way to cool down something very hot - like the machines used in industrial processes. 

To cool down a campfire, you usually just need a bucket of water. Of course, for a factory, this requires very large quantities of water, which is then released back into the environment. Usually, it still has an elevated temperature and then can contribute to thermal pollution. 

 Source: Victor on Unsplash

Urban runoff and its impact on water temperature

Cities are densely packed squares of concrete, asphalt, people, and cars. This all produces tons of heat, which gets trapped by the building materials and creates "urban heat islands." 

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Tokyo is one of the best-studied of these heat islands. Temperatures are significantly warmer there than in surrounding areas, thanks to the intense amount of heat generated for the population. The building materials absorb heat, further warming the city. 

The thermal effects of this thermal pollution alter the surface temperature of Tokyo Bay. This is a classic example of urban environments affecting the water sources upon which they depend for their very survival. 

Another problem is urban stormwater runoff. When the drainage system of a city or developed area isn't planned out well, a storm can cause a flood of water to be washed from the city into the local water supply. The water coming from the city is warmer than the local water supply because of the urban heat island effect.

This has been an ongoing problem for the Severn River in Maryland. Sudden washouts sweep large amounts of water into the watershed, causing degradation of water quality in the area. 

Source: Severn River Association 

Is there cold water pollution?

Yes. Hydroelectric dams often release unnaturally cold water into a river or lake at the bottom. This sudden change in temperature decreases the ability of fish, microorganisms, and other creatures to survive. 

Though heated water is the more common issue, any creature outside its ideal temperature range can be killed by the water changing too many degrees one direction or the other. 

How Does Thermal Pollution Affect Aquatic Ecosystems?

All ecosystems exist in a delicate balance. Large bodies of water contain millions of different life forms that all depend on one another for survival. Since humans are so dependent on natural bodies of water, we are part of these ecosystems too. 

Impact on oxygen levels in water bodies

One of the key negative effects of thermal pollution is that it decreases the level of dissolved oxygen in the water, contributing to anaerobic conditions. This means there's often not enough oxygen in the water to sustain life forms. 

Effects on fish and other aquatic organisms

Most living things are extremely sensitive to their environment's temperature. A rapid increase or decrease in temperature can dramatically change the fish population. Hotter temperatures speed up fishes' metabolism, often causing them to die off. 

Thermal pollution can also affect the microorganisms living in a water source - bacteria, algae, fungi, and more are all affected by the warming of water. 

Disruption of natural breeding cycles and migration patterns

Living things will instinctively try to find a habitat that's better suited for them to live in. Thermal pollution causes either a rapid increase or decrease in a given type of living in the water habitat. Some organisms, like native, might migrate to find a healthier environment. This makes space for invasive species or uncontrolled growth of other organisms, like toxic algae. 

Source:  Marcos Paulo Prado on Unsplash

What are some examples of thermal pollution in action?

Thermal pollution is a well-studied phenomenon, and the effects are only increasing as our society becomes more energy-hungry. 

A few recent examples show how the change in the physical water source has wide-reaching consequences. 

Case study: thermal pollution in rivers and lakes

Power plants are commonly built near lakes and rivers. This is because the water makes a handy source of coolant. In the case of hydroelectric power, the movement of the water itself generates the energy.

Though efforts are usually made to cool the water before returning it to its source, it is generally still warmer than before. 

Case Study: Illinois Power Plants: A recent survey showed that 98% of the surface water in Illinois is used for power plants. This meets the needs of Illinois's growing pollution. When this water is returned to its original river sources, however, it has a slightly elevated temperature. We know that thermal pollution is a result. 

Case study: Thermal pollution in coastal areas and its effects on marine life

When seawater is used as a coolant by power plants, there are consequences for the surrounding life forms. 

Case study: In the Mediterranean Sea, scientists studied the ecosystems living on the rocky reefs near a coal-fired power plant. They concluded that different life forms were living on the reefs near the power plants than the ones not near power plants. 

We know that the power plants are affecting the kinds of creatures that can survive nearby. 

The Jerusalem Post

Are There any Natural Causes of Thermal Pollution?

Thermal pollution may happen from natural causes too. Warmer water is released from geothermal activity, volcanic activity, droughts, floods, or excessive sunshine. The effects on the ecosystem are usually temporary and more limited in geographic area than the effects caused by human pollution. 

Volcanic activity and geothermal vents

Volcanic and geothermal activity moves intensely hot air, rock, lava, and water around the planet. This can affect the entire landscape. Scientists are currently studying the "Ring of Fire" volcanoes and how the heat they release changes the microorganisms in the area.

While this might seem less important than flowing rivers of lava or mudslides, microorganisms affect all life on the planet - including humans.

READ NOW: Yellowstone Volcano: Eruption Risks and 2024 Geological Insights

 Climate change and its role in increasing water temperatures

Power plants cause thermal pollution on a local basis - by dumping heated water back into the local water supply. For example, the Persian Gulf has demonstrably higher temperatures because of the Bandar Abbas Thermal Power Plant. 

Global warming refers to the effects the entire planet is experiencing thanks to the rise of heat-producing emissions caused from manufacturing, vehicles, and deforestation.

Any area experiencing the ill effects of thermal pollution is also affected by the overall rise in temperature across the whole planet, leading to a compounding effect.

How Can We Control and Mitigate Thermal Pollution?

There are some things that power plants and industrial manufacturers can do to protect the temperature of water bodies they use for coolant. 

The key element is figuring out a water cooling system that reduces the heat of the water used for industrial processes. 

Technological solutions for reducing heat discharge

One common method for preventing thermal pollution is to create a closed system.

This means that the water used in the power plant or factory is circulated within the compounds itself, without being released back into the ecosystem. 

Other solutions include:

• Refrigeration 

• Chemical treatment

• Filtration through wetlands 

Regulatory measures and environmental policies

Local governments control the permit system. Industries, wastewater treatment plants, and large-scale farming operations are all required to obtain permits if their operations will release any kind of pollutant into the water supply. This protects the local population and ensures that costs are paid for by the power station or factory creating the pollution. 

In the United States, the Federal Clean Water Act regulates indirect and direct thermal pollution. Often, this law isn't sufficiently enforced to prevent damage from the heat receiving water bodies. 

The role of cooling ponds and other heat management techniques

Some industries use cooling towers or cooling ponds to cool water before releasing it. This is a popular method because it requires less energy to cool down the water compared to mechanical methods like refrigeration or heat pumps. 

Artificial ponds or lakes are built to give the wastewater a place to cool before reusing it as a coolant or recycling it into the water system. Some of these ponds do eventually host fish and other organisms adapted to warmer water. They tend to feature a lack of biodiversity, however, as many organisms adapted to particular temperature ranges can't adjust to the frequent influxes of hot or cold water. 

What is the Future Outlook for Thermal Pollution?

Water may well become one of the most hoarded substances on the planet if a sustainable method to keep the supply clean is not found. 

Solutions to thermal pollution involve innovation, cooperation, and regulation. It's unlikely that a power-hungry civilization will slow its use of water as a coolant in the near future. It's crucial to continue research to find efficient methods of cooling water and manage any damage to the wildlife damaged by thermal shock. 

Emerging challenges in thermal pollution control

One concern with the advent of artificial intelligence is the intense amount of energy it takes to power generative AI servers. Both the production of enough electricity to run the servers and the cooling of the servers themselves require massive amounts of cool water. 

Innovative approaches to addressing thermal pollution

Thanks to the First Law of Thermodynamics we all had to learn in high school, energy isn't created or destroyed - it just changes form.

Though the extra heat discharged from power plants is called thermal pollution, it can be harnessed to warm areas that need the extra energy - like warming greenhouses to grow crops, or providing heat for a building.

Efficient uses of heat have a double positive impact. Not only do they provide warmth (which all of us pay for, as reflected by winter heating bills), but direct the heat away from delicate aquatic ecosystems.

The Bottom Line

It's currently estimated that about 70% of human-created energy is wasted. If that energy can be converted into necessary projects like warming buildings, we could save money and reduce the environmental impact.

Source: UMC

While thermal pollution is a growing challenge, the technology exists to handle our water supply efficiently and responsibly, ensuring the safety of our water supply for future generations.