Kevin French, age 13, of Hodgenville, Kentucky, for his question:
What is thermal pollution?
Thermal, of course, refers to heat and thermal pollution threatens our ecology by adding extra heat to the environment. Host of it is water used by power plants to cool off their steam condensers. All life processes depend on temperature and plants and animals are adapted to the normal seasonal variations in their environments. But sudden thermal changes upset their life processes and extreme changes are fatal. When thermal pollution adds extra heat to a waterway, the change in the aquatic environment upsets the delicate balance of nature in many ways.
A steam power plant needs heat to turn its generators and streams of cool water to carry away surplus heat. This problem is solved by piping water from a nearby stream or lake, using it to cool down the condensers and letting it return whence it came. However, the water acts as a coolant by absorbing the surplus heat and it returns perhaps 20 or 30 degrees hotter than it was. To some extent it is dispersed by moving water and lost to the air. But more often it raises the normal temperature of the aquatic environment, causing a series of biological changes in plant and animal life.
As a rule, a rise in temperature speeds up metabolism and heart beat. In most fishes, these rates double when the water becomes 18 degrees Fahrenheit warmer than normal and more oxygen is needed. Most fish need 2 1/2 times more oxygen when the temperature rises 30 degrees Fahrenheit, but at the same time their blood can absorb less. The heart beats faster and extreme stress can make it stop. Surplus heat also speeds up digestion in fishes, while reducing the value they get from their food.
In nature, temperature changes play a key role in reproduction. Thermal pollution can upset the spawning schedule of aquatic animals and also prevent cell division in the eggs. It also may favor the growth of undesirable plants and decay bacteria. This reduces available oxygen and creates foul water that clogs the gills of fish and shellfish. These are but a few things that thermal pollution can do. In studying the problem, ecologists use a special infrared camera to detect the flow and temperature of this unhealthy water.
At present, thermal pollution is confined mainly to waterways used by large power plants. But the problem will increase as people use more power and the population multiplies. It is estimated that the many huge nuclear power plants needed in the future could add thermal pollution to one third of our running water. However, at last the ecologists are being heard and heeded. It is nice to know that many plans are being made to stop this particular pollution problem before it gets seriously out of hand.
It seems sensible to make use of this wasted heat, perhaps in agriculture, in sewage treatment or desalting plants. Another suggestion is to limit a power plant to using water from its own specially cooled lake. Other plans suggest evaporating the steamy water in tall towers. This could add one per cent to our light bills ¬and foggy vapor to the air. For a charge of two and a half per cent, there is a plan to solve the vapor problem. Naturally, we expect the solution to require money and brainwork. But those of us who care know that these are minor items when compared with the further pollution of our planet.