We rarely realize the real worth of water till we run out of it. We have always been blasé about the presence of water and never even considered if there is a possibility that it might dry out one day. And one form of pollution that normally eludes our mind is thermal pollution.
With innumerable thermal industries and power plants mushrooming all around, thermal pollution and its consequences are here to stay and pose a persistent and real problem in modern times.
The thermal problem in its broadest definition is the sudden change in the ambient temperature of a natural body of water through human interference. The quality of the body of water is decreased by a rise or fall in the water temperature, This degraded water is infirm to support the life-support systems of marine life or consumption.
It can be as small as a backyard pond or even a large river or a part of the ocean.
Thermal Pollution And Its Sources
Heated wastewater discharged from manufacturing and production plants is the major source of thermal pollution. They include natural gas plants, coal-powered thermal power, nuclear plants, paper, textile pulp factories, and a host of other plants.
Such factories use up a large volume of water as a cooling agent. This helps to cool down the heat engines and generators. Water thus acts as a sink for excess heat. This heated water gets released to its source, which, in most cases, is a natural source of water. This change in the temperature of a natural body of water degrades its equilibrium and is a cause of thermal pollution.
Another significant cause of thermal pollution is deforestation or the removal of vegetation from a water body. Vegetation in and around water bodies serves to maintain the temperature at an ambient level. With the cover taken away, the degraded water bodies absorb sunlight and heat, raising the water temperature.
Desalination plants are a major source of thermal pollution along seashores. These plants are mostly clustered together and discharge huge volumes of heated water with high brine content into shallow seas. This raises the salinity and temperature of the surrounding seas.
Thermal pollution is also caused when water bodies become shallow due to soil erosion. It significantly raises the water temperature.
Geothermal activities or volcanic eruptions on land or oceans also increased the temperature of the water. The surrounding lava eruption faces a sharp rise in water temperature. But surprising, certain marine life has been found to thrive around areas of lava activity.
Thermal Pollution And Its Ecological Impact
Thermal pollution does not get the same attention as other forms of pollution such as chemical, solid waste, or carbon emissions. But scientists have spoken up about the ecological threat that thermal pollution pose.
Aquatic life is as sensitive to changes in the temperature of a water body as it is to chemical or other changes. Even a slight increase in temperature affects the oxygen content of the water and makes it difficult for them to survive and breed in such water.
The direct impacts of thermal pollution are multiple and include a decrease in the oxygen content of the water. With each rise in temperature, the oxygen content of water dissolved in it goes down. This oxygen deficit, or anaerobic, proves immensely harmful to aquatic life.
Organic components present in water also decompose at a faster rate in higher water temperatures, further depleting the oxygen content.
Aquatic animals and organisms are adapted to function in a very limited temperature range. They suffer thermal shock when exposed to temperatures outside the range to which they are accustomed. This explains mass killing in places where no chemical presence has been detected.
Marine insects and plants are also equally sensitive to such thermal pollution. Sponges, crustaceans, and mollusks die out when temperatures go above 37C.
In contrast, certain organisms exhibit a sudden rise in activity and numbers with an increase in water temperature. This disrupts a stable food chain in the marine ecosystem and changes the environment’s balance. Thermal pollution also adversely affects aquatic animals’ reproductive systems.
Thermal pollution also triggers a mass exodus of marine life forms from areas of thermal pollution and creates a dead water body in affected areas. Lack of food and oxygen forces even those marine life forms that are relatively unaffected to move to cooler waters.
Corals are also highly vulnerable to thermal pollution. Corals harbor a teeming marine world, and they are bleached by a rise in water temperature from effluents and run-offs. The resulting expulsion of symbiotic algae, that live within the digestive cavity of the coral polyp, spells doom for the corals.
46M adult fish and 2.1B eggs, young fish, and larvae are killed every year, affected by effluent discharge from the First Energy Bay Shore Plant in Ohio. Michigan’s Monroe Power Plant is also responsible for the death of around 25M fish every year.
Controlling Thermal Pollution
Several scientific techniques can be used by industrial units to control thermal pollution through the creation of artificial lakes, cooling towers, and cooling ponds.
One of the most effective methods and simplest to control thermal pollution is through cooling ponds. Warm discharge from the plants is stored in a holding pond to be cooled and then discharged into water sources. The evaporation process dissipates the heat quickly enough.
Cooling towers are also installed in steel plants, chemical processing plants, and manufacturing units where the effluents need to be cooled before they are discharged into the water.
Cooling towers function through the rising recirculation of cascading hot water through the cooling towers into the atmosphere through the process of evaporation.
But there are concerns about the impact of large cooling towers on the atmosphere as a large amount of water vapor is poured into the atmosphere.
Governments have a big role to play in regulating thermal pollution through the framing of stringent laws. This is especially important in developing nations, as laws are not in place for controlling thermal pollution and wastewater treatment. A strong and effective government monitoring agency is needed for constant observing of effluent discharge from various industrial sectors.
In the US, the Clean Water Act regulates matters related to thermal pollution. It requires states to specify limits on thermal discharges from plants. Industrial plants must also match specifics on temperature discharge standards before they are allowed to get the permit. Alternatively, they must prove that the discharge temperatures have no adverse effect on the environment.
There is a marked shift away from the process of once-through cooling, the practice of passing water through condensers to remove excess heat. This is because it promotes thermal pollution and the strain it puts on marine and aquatic life while putting a strain on a precious commodity.
California was the first state to enact regulations to phase out this process. There are emerging technologies for mitigating the thermal pollution of industrial sources and power plants. The processes include reducing the water used in these facilities and also capturing the heated water for other uses such as desalination, thus reducing discharge.