Combustion of fuels for electricity generation and vehicle propulsion is a key source of thermal pollution, harming aquatic life and causing global warming.
It is a well-admitted fact that burning of fossil fuels in power plants, industrial furnaces and vehicle engines causes air pollution. However, a lesser known impact linked with these power generation processes is thermal pollution. Thermal pollution refers to the addition of large amounts of waste heat to the environment; the causes of thermal pollution are almost the same as those causing air pollution.
Causes of Thermal Pollution
From motor vehicles to most of the electricity produced at power plants, the primary form of energy involved is heat. The device that converts heat into other useful forms of energy is called a heat engine. A common example of a heat engine is a car engine in which heat energy is released from oil burning converting into mechanical energy or motion.
Like any real-world process, combustion of fuels and subsequent conversion of heat into other energy forms are imperfect. The inherent inefficiency of energy conversion processes results in heat losses to the environment. The heat addition to the environment poses serious threats to humans, animals and plants.
Even though nuclear power plants do not cause air pollution, they are a conspicuous source of thermal pollution. Nuclear power plants are usually built near large water reservoirs such as lakes, rivers or oceans due to requirement for cooling water. Although the water used for cooling purposes in plant condensers is recycled before returning to the source, its temperature remains significantly high and may have severe impacts.
Effects of Thermal Pollution
The residual heat released by power plants adds to the environment and impacts its inhabitants harshly. Since hot water holds relatively less oxygen; many species in these habitats face difficulty in survival.
Water heating due to thermal pollution alters marine ecology to a great extent; hotter water favors some species while it is harmful to others. In a similar way, during nuclear plant startup, shutdown for repair and maintenance and then sudden startup creates abrupt temperature changes in water contained in lakes. These thermal shocks can be lethal for certain aquatic species.
Like other species, aquatic animals and plants have evolved with biological systems that can function best within a certain temperature range. The sudden discharge of heated water to lakes, rivers and oceans causes damage to the habitats of aquatic organisms by affecting their metabolic functions; the oxygen dissolving ability of hot water decreases and thus, as the water temperature rises significantly, it disrupts the food web by killing fish and other heat-sensitive living organisms.
Most animals living in water are cold-blooded by nature and cannot maintain their body temperatures; therefore, a temperature rise in their natural surroundings has serious implications upon their biological functions. For instance, thermal shocks of mild intensity can result in reproductive disorders among fish, thereby affecting the biodiversity of aquatic ecosystems.
In addition to thermal water pollution, cooling towers used in power plants release heat directly into the atmosphere, which raises the air temperature drastically, thus contributing to global warming .
How to Control Thermal Pollution
The problem of thermal pollution is unavoidable. It can be reduced, however. Engineers can make efforts to ensure minimum heat losses by improving thermal efficiencies of heat engines. Nonetheless, the best solution is to reduce consumption of fossil fuels and to limit day-to-day energy usage. The development of alternative energy resources such as solar power, wind energy and hydropower can also be beneficial.