Thermal pollution occurs when hot wastewater is discharged into such bodies of water as rivers, lakes, and oceans as a result of human activity. Thermal pollution can also occur in ground water (water held beneath the ground). The wastewater raises the temperature of the water, which can harm animals and plants living in it. Warmer water can hurt fish by interfering with their growth, reproduction, and food supply. In some cases, the sudden rise in temperature can kill fish. Warmer water may also attract foreign plants, animals, and other organisms that can harm an area’s native species.
Factories and power plants that use water to cool equipment or heat water to produce steam rank as the major sources of thermal pollution. Many countries have laws controlling the discharge of wastewater by these facilities. Factories and power plants often reduce thermal pollution by cooling wastewater in special cooling towers before releasing it, enabling heat to escape into the air. They can also release hot water in scattered areas to prevent a dangerous temperature rise in any one place.
