Thermal Pollution: Returning Water To The Ocean

Thermal pollution is the degradation of water quality by any process that changes the ambient temperature of a natural body of water. It is caused by human influence and is sometimes called thermal enrichment. The most common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water is used as a coolant, it is returned to the natural environment at a higher temperature, which decreases the oxygen supply and affects the composition of the ecosystem. This can be harmful to aquatic animals, such as fish and amphibians, as well as microorganisms, and can also kill vegetation that grows alongside the water.

Power plants and manufacturers use water as a coolant

Power plants, including nuclear power plants, use water as a coolant to remove heat from their reactors. For example, the Fukushima Daiichi nuclear plant in Japan normally used purified water to cool its reactors. However, after the 2011 tsunami, the plant had to resort to using seawater to cool the fuel rods and prevent a complete meltdown. While seawater can be used as an emergency coolant, it is considered a last resort as it can damage the reactor cores and make them unusable. The use of seawater and boron, a strong neutron absorber, can be employed to suppress fission chain reactions in fuel elements during emergencies.

Manufacturers and factories also use water as a coolant to lower the temperature of their machinery and equipment. After using the water for cooling, it is often released into nearby rivers, lakes, or oceans. This water is typically warmer than the receiving water body, leading to thermal pollution. The increased water temperature can disrupt the natural life cycles of aquatic species, including breeding, feeding, and migration.

To mitigate the impact of thermal pollution, industries can implement several measures. One approach is to cool the water before releasing it into the environment. This can be achieved by using special cooling systems or building cooling ponds that allow water to cool off naturally. Another strategy is to avoid using water for cooling altogether and instead opt for air cooling or dry cooling systems that use a minimal amount of water, which can be collected and reused.

Additionally, upgrading outdated machines and equipment can help prevent excess heat from entering water systems. Proper environmental planning and better cooling system designs can also contribute to reducing thermal pollution. By adopting these measures, industries can play a crucial role in protecting aquatic life and maintaining the balance of ecosystems.

Urban runoff from roads and parking lots

The water that runs off these impervious surfaces picks up a range of contaminants, including gasoline, motor oil, heavy metals, trash, and other pollutants from roadways and parking lots. Roads and parking lots are particularly associated with polycyclic aromatic hydrocarbons (PAHs), which are byproducts of gasoline and other fossil fuel combustion. Additionally, fertilizer use on residential lawns, parks, and golf courses can result in high levels of nitrates and phosphorus in urban runoff when improperly applied or over-fertilized.

The impact of urban runoff from roads and parking lots extends beyond water pollution. It also contributes to flooding, as the large volumes of water that accumulate on these impervious surfaces are quickly directed towards drainage systems and nearby water bodies. This sudden influx of water can overwhelm drainage systems, leading to basement backups and water seepage into buildings.

To mitigate the effects of urban runoff from roads and parking lots, local governments employ various stormwater management techniques, known as Best Management Practices for water pollution (BMPs). These techniques aim to control water quantity and improve water quality. Pollution prevention practices include low-impact development (LID) or green infrastructure techniques, such as Sustainable Drainage Systems (SuDS) or Water-Sensitive Urban Design (WSUD). Implementing green roofs, improving chemical handling practices, and utilizing runoff mitigation systems like infiltration basins and bioretention systems are also effective strategies.

Educational programs and discussions about urban runoff and responsible waste disposal practices can empower local businesses and individuals to play a role in reducing pollution. Additionally, street-sweeping programs can effectively improve the quality of urban runoff by collecting dust, solid particles, and pollutants from roads and parking lots before they enter the stormwater system. By combining these strategies and implementing effective city programs that address the specific needs of the community, the impact of urban runoff from roads and parking lots on the environment can be significantly reduced.

Natural causes include volcanoes and lightning

Natural events and human activities can cause thermal pollution, which is any sudden change in the temperature of a natural body of water. Natural causes of thermal pollution include volcanoes and lightning.

Volcanoes are one of the primary natural causes of thermal pollution. Volcanic eruptions release large amounts of volcanic gas, aerosol droplets, ash, and heat into the atmosphere and oceans. While the ash from volcanic eruptions typically falls rapidly and has minimal impact on climate change, the gases and heat released can significantly affect ocean temperatures. For example, the injection of sulfur dioxide and carbon dioxide gases into the stratosphere can cause global cooling and warming, respectively. The cooling effect of volcanic eruptions on ocean surfaces usually lasts for several years, but the impact on the subsurface ocean can persist for much longer and influence decadal variabilities such as the Atlantic Meridional Overturning Circulation (AMOC).

In addition to volcanoes, lightning can also contribute to thermal pollution. While the direct impact of lightning on ocean temperatures may be negligible, it can indirectly affect water temperature by triggering wildfires. Wildfires can lead to thermal pollution by removing shade from lake shores and riverbanks, exposing the water to more sunlight and causing it to heat up.

It is important to note that the impact of natural causes of thermal pollution, such as volcanoes and lightning, can be exacerbated by human activities. For example, climate change influenced by human actions can increase the frequency and severity of wildfires, leading to more significant thermal pollution in water bodies.

Soil erosion and deforestation near bodies of water

Soil erosion is a natural process, but human activities such as deforestation, agriculture, and inappropriate land use can accelerate it. Deforestation removes the tree roots that hold soil together, making it more susceptible to wind and water erosion. Tree roots and forest vegetation also aid in capturing and slowly releasing rainwater, preventing heavy rains from running off quickly and carrying away fertile soil into rivers and streams. This process leads to increased sedimentation and pollution in waterways, clogging these water bodies and causing declines in fish and other species.

Deforestation near bodies of water can also contribute to thermal pollution. Without tree cover, the shores of lakes and rivers are exposed to more sunlight, causing the water to heat up. This phenomenon is especially relevant in urban areas, where hot city streets and buildings transfer their excess heat to the water during rainstorms. This runoff water ultimately makes its way into nearby streams, rivers, and sewer drains that lead to the ocean, increasing the temperature of these water bodies.

The effects of soil erosion and deforestation near bodies of water extend beyond the immediate loss of fertile land and increased water temperatures. The sedimentation caused by soil erosion can alter the water chemistry, affecting the delicate balance of aquatic ecosystems. It can also lead to eutrophication, a process where excess nutrients cause harmful algal blooms and deplete oxygen levels, further stressing aquatic organisms.

To mitigate the impacts of soil erosion and deforestation near bodies of water, sustainable land use practices and reforestation efforts are essential. Agroforestry, contour ploughing, terracing, and minimal tillage are techniques that can help protect topsoil and maintain water quality. Additionally, integrating trees within farmland and implementing better cooling systems for industrial wastewater can help reduce the temperature of water before it is released back into natural water bodies, thus minimizing thermal pollution.

Petroleum refineries and chemical plants

Thermal pollution, also known as "thermal enrichment", is the degradation of water quality by any process that changes the ambient water temperature. It is caused by a rise or drop in the temperature of a natural body of water due to human influence. Most cases of thermal pollution involve excess heat, although too much cold water can also cause problems.

Petroleum refineries, along with other industrial facilities, contribute to thermal pollution. They use water to cool machinery and discharge water at elevated temperatures. This process is called "once-through cooling" or OTC, where cold water passes through the plant once and leaves as heated wastewater. A large power plant may withdraw and export as many as 500 million gallons of water per day, with the discharged water being 10 °C (20 °F) warmer on average.

The heated water from petroleum refineries and other industrial sources can be controlled through cooling ponds, which are man-made bodies of water designed for cooling by evaporation, convection, and radiation. However, the best way to address the problem of thermal pollution is to eliminate once-through cooling systems altogether. This can be done by not using water for cooling, cooling the water before discharge, or not discharging the water at all. Dry cooling systems, which use a small amount of water and rely mostly on a flow of moving air for cooling, are an alternative.

In addition to the direct effects of heated water discharge, petroleum refineries and chemical plants can also contribute to thermal pollution through their day-to-day operations. These industrial plants produce high amounts of domestic sewage effluents, which can contain dirty water used for various purposes such as washing clothes or cooking meals. The wastewater from these plants can contain harmful chemicals, fuels, solvents, heavy metals, and radioactive materials, further degrading water quality.

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