We have always associated pollution with conventional forms such as carbon emissions, chemical discharge, and plastics. But another form of pollution associated with industrialization is proving to be just as deadly, especially to marine life forms in all water bodies, including the oceans.
Thermal pollution has proved to be a persistent and real problem in modern human society. Defined in layman’s terms, it is the discharge of heated water from industrial installations into nearby water bodies. This harmless activity has led to the destruction of marine life in many large water bodies, including rivers and oceans.
The ejected water that enters the water bodies has depleted levels of oxygen, which has a disastrous effect on the marine ecosystem. Thermal pollution leads to a sudden change in water temperature, which is outside the zone in which marine life can survive and reproduce.
Cause Of Thermal Pollution
Thermal cooling is normally associated with factories and power plants that take in water to cool down their super hot machinery. This discharged water enters the natural source and, if untreated, causes maximum damage. Thermal pollution is also the result of soil erosion which leads to water bodies turning shallower, thus increasing the temperature of the water.
The destruction of vegetation around water bodies and also marine vegetation also affects the temperature of water bodies and is a source of thermal pollution.
But the biggest source of thermal pollution remains manufacturing and production facilities, and thermal and nuclear power plants. These facilities are built near water sources to take in water to cool down their machinery. Water taken in from these sources is then released into the source, mostly untreated. As the warm water flows out to the water bodies, there is a spurt in temperature, which, though in single digits, does harm in multiple ways.
The greatest change caused to water by rising temperature is the amount of oxygen it can hold. As water bodies turn warmer, the oxygen level falls and there are fewer habitable areas for marine life to survive.
Though marine life forms can adjust to a slightly higher temperature than the normal temperature they are used to, the greatest negative effect of thermal pollution is the depletion of oxygen levels and the disruption of the food chain.
Marine creatures, including coral, are already living in the warmest possible temperatures. The depletion of the source of food also makes them move away from these water stretches and causes dead water bodies. Intense competition builds up and many weaker marine life forms lose out and become extinct in such areas.
Thermal pollution services reduce the quality and variety of marine life forms, which ultimately leads to the destruction of habitats if not controlled.
Soil erosion caused by deforestation is a major factor leading to thermal pollution. The depletion of forests is a reality and soil erosion is a direct result of it. Constant soil erosion forces the water bed to rise and proves fatal to the aquatic life forms as it gives rise to the disappearance of oxygen at a level that is greater than being produced by the process of photosynthesis.
Deforestation is another major cause of thermal pollution. Plants and trees prevent sunlight from reaching water bodies directly and keep them cool. Deforestation affects it in two ways.
While it allows sunlight to directly reach the water body like lakes, ponds, and rivers, the lack of forest cover also raises the mean temperature of the region, which also serves to increase the water temperature. It leads to the concentration of greenhouse gases, taking away the oxygen present near water bodies.
Urban runoff is another phenomenon that is not given the attention it deserves. Large parts of urban areas are paved. Rainwater running on these surfaces tends to be much warmer, especially in tropical regions. This runoff eventually runs into sewers and flows out to water bodies.
There are natural sources like geothermal activities, volcanoes, and hot springs. Though they are confined in their activity, they give out intense heat from molten lava and hot springs that raise the water bodies’ temperature.
Lightening also introduces a colossal amount of heat and energy into water bodies. There has been an increase in lighting linked to high levels of pollution and global warming. It also contributes to the heating up of water bodies.
Retention ponds are another cause of thermal pollution. The small water bodies absorb a large amount of heat from sunlight. And when the water from such ponds is directly pumped into larger water bodies, it leads to a significant jump in temperature. Domestic sewage also adds to the temperature of water bodies, especially if it is allowed to flow untreated into larger water bodies.
The Inimical Effects Of Thermal Pollution
Scientists have highlighted the negative of thermal pollution, a subject that has not been given the attention it deserves. It has a detrimental effect on all water bodies, from small ponds to oceans. The effect of thermal pollution on the ecosystem outweighs the benefits it imparts.
The reduction in the level of dissolved oxygen in water is the greatest negative of thermal pollution. Oxygen depletion is rapid with the rise in water temperature and suffocates plants and marine life forms.
Thermal pollution also leads to a decrease in the ability of marine lifeforms to stave off diseases. Coral, one of the most thriving areas of marine life, has been severely bleached in many spots. The Australian Great Barrier Reef has seen more than half of its coral destroyed due to thermal pollution as rising climate temperatures have destroyed the once pristine marine world forever.
Controlling Thermal Pollution
Nations have realized that thermal pollution can be as harmful to marine life forms as other conventional pollution. Climate change has already aggravated the water temperature, leading to the melting of ice caps in the polar region.
There has been a heightened increase in industrial activity in the past 4 decades. Around one-third of the total power generation of Americans comes from power plants that have so far been dependent on once-through cooling, a system of cooling large machinery by having water passed through them.
A study initiated in 2016 showed that over half of the thermal pollution affecting freshwater is due to coal and nuclear plants, relics from the 70s and 80s. Thermal discharge is being regulated in the US through the Clean Water Act. It requires states to set a limit on the amount of thermal pollution from each plant. Permits are being issued now based on the compliance of these factories and plants.
California was the first to introduce a regulation to phase out water cooling systems, the main cause of thermal pollution. The process includes limiting the water that can be discharged by such units and also making facilities to capture and recycle hot waste water for other purposes like desalination. This ultimately limits the volume of discharge from every plant.