Thermal Pollution

Waste Heat - A pollutant as dangerous to waters as more tangible of forms of waste Human activity can change normal temperature: By altering environment of watercourse: Road building , logging, poundments, diverting flows for irrigation Adding or removing heat. On national scale, industrial cooling waters is a first-order source of heat. Electro power generation uses 80% of cooling waters. Best single index of thermal pollution lies in projecting future electric power generation. Past experience has indicated that thermal pollution has not multiplied as fast as power generation because of improvements in thermal plant efficiency and developement of hydropower. Nulear plants - waste even higher proportion of heat than fossil-fuel plants. Heat rejection is expected to increase nine fold by the year 2000. Problem is one of managing tremendous amounts of waste heat in a manner that will maintain or enhance, physical, chemical and biological nature of our water resources.

Effect of Thermal Pollution:

Warm water typically decreases the level of dissolved oxygen in the water. The decrease in levels of dissolved oxygen can harm aquatic animals such as fish, amphibians and copepods. Thermal pollution may also increase the metabolic rate of aquatic animals, as enzyme activity, resulting in these organisms consuming more food in a shorter time than if their environment were not changed. An increased metabolic rate may result in food source shortages, causing a sharp decrease in a population. Changes in the environment may also result in a migration of organisms to another, more suitable environment, and to in-migration of organisms that normally only live in warmer waters elsewhere. This leads to competition for fewer resources; the more adapted organisms moving in may have an advantage over organisms that are not used to the warmer temperature. As a result one has the problem of compromising food chains of the old and new environments. Biodiversity can be decreased as a result.

In the 1970s there was considerable activity from scientists in quantifying effects of thermal pollution. Hydrologists, physicists, meteorologists, and computer scientists combined their skills in one of the first interdisciplinary pursuits of the modern environmental science era. First came the application of gaussian function dispersal modeling that forecasts how a thermal plume is formed from a thermal point source and predicts the distribution of aquatic temperatures. The ultimate model was developed by the U.S. Environmental Protection Agency introducing the statistical variations in meteorology to predict the resulting plume from a thermal outfall.

Coal-burning power plants are known producers of thermal pollution in nearby bodies of water that they use as cooling ponds. This research focused on the effects that thermal pollution caused by the Marshall Steam Station had on Lake Norman, North Carolina. It was found that dissolved oxygen in the steam station's discharge cove was decreased by approximately four mg/L as compared to a site ten miles upstream, and was decreased by about three mg/L as compared to a cove several hundred yards downstream. Temperatures of the surface water in the discharge

How to control Thermal Pollution

Following are the means to reduce thermal pollution:

1. Theoretically, when efficiency of any heat engine is equal to 1.0 then it will convert 100% of heat energy to mechanical energy. So there will be no loss of heat to the environment. This is practically impossible. Rather, we should aim at maximizing the efficiency of heat engines (steam, IC, nuclear etc) so that heat loss is minimum.

2. Reduce mechanical friction in any rotating parts.

3. Avoid consuming energy more than necessity. Burn less coal, oil or gas.

4. Temperature signal conditioners accept outputs from temperature measurement devices such as resistance temperature detectors (RTDs), thermocouples, and thermistors. They then filter, amplify, and/or convert these outputs to digital signals, or to levels suitable for digitization

5. Industrial fans and industrial blowers and commercial fans and blowers are designed to move air and/or powders in industrial and commercial settings. Typical applications include air circulation for personnel, exhaust or material handling.