168 Ecology and Applied Environmental Science
components can affect food chains through aquatic organisms. If hydrocarbons enter the bodies of fish, they can give their flesh an unpleasant
taste. Apart from the toxic effect, they damage the feathers of seabirds and
may be the main cause of the drastic decrease that has been noted in the
populations of certain species of birds. The biological breakdown of oil
may also cause oxygen depletion in seawater.
8.7 thErMal Pollution
The warm wastewater from power stations and other industries may cause
a rise in the temperature of receiving water which aquatic ecosystems
are unable to tolerate. This phenomenon is known as thermal pollution
(Chapter 2). In the United States, about 75–82% of thermal pollution is
generated by power plants. Some countries require limits on discharges
that lead to thermal pollution of receiving waters, although this aspect of
water pollution has proven to be more elusive than conventional chemical
discharge. Regulation may take different approaches; some laws require a
best practice, such as the use of cooling ponds or cooling towers for waste
heat discharge. In other cases, a numerical limit on acceptable temperature increase in the receiving waters is applied. For example, the World
Bank standard provides a maximum increase of 3°C at the margin of the
mixing zone. The US EPA has recommended that temperature increases in
receiving water do not exceed 0.8–2.8°C. The lower value refers to the sea
in summer and the higher value to watercourses.
components can affect food chains through aquatic organisms. If hydrocarbons enter the bodies of fish, they can give their flesh an unpleasant
taste. Apart from the toxic effect, they damage the feathers of seabirds and
may be the main cause of the drastic decrease that has been noted in the
populations of certain species of birds. The biological breakdown of oil
may also cause oxygen depletion in seawater.
8.7 thErMal Pollution
The warm wastewater from power stations and other industries may cause
a rise in the temperature of receiving water which aquatic ecosystems
are unable to tolerate. This phenomenon is known as thermal pollution
(Chapter 2). In the United States, about 75–82% of thermal pollution is
generated by power plants. Some countries require limits on discharges
that lead to thermal pollution of receiving waters, although this aspect of
water pollution has proven to be more elusive than conventional chemical
discharge. Regulation may take different approaches; some laws require a
best practice, such as the use of cooling ponds or cooling towers for waste
heat discharge. In other cases, a numerical limit on acceptable temperature increase in the receiving waters is applied. For example, the World
Bank standard provides a maximum increase of 3°C at the margin of the
mixing zone. The US EPA has recommended that temperature increases in
receiving water do not exceed 0.8–2.8°C. The lower value refers to the sea
in summer and the higher value to watercourses.