How to control Thermal Pollution?



1. To control the atmospheric pollution, pollution norms for environmental factors in gen and for the air in particular, should be established. These control norms should be adopted. Strictly the incidence of illness among the population should also be taken as the main criterion in the assessment of the harmful effects of atmospheric pollutants.

The standard of air quality is based on the maximum permissible (safe) concentration (M for various toxic substances. The MPC of atmospheric pollutants are generally established indices: as either the highest single concentration (in 20 minutes) or the average daily concentrate: (in 24 hours). The latter is the principle index to prevent the unfavourable effect of pollutant which may result from long exposure in some countries.

The MPC (mg/m3) of some typical contaminants present in effluents of thermal stations at populated areas on average daily concentration basis are as follows: non-toxic du 0.15, sulphurous anhydried -0.05, carbon-monoxide -1.00, nitrogen dioxide -0.085, soot (flj ash) -0.05. Hydrogen sulphing -0.008, and benzapyrine -0.1 ug/100m3 it is essential that concentration of each of these pollutants should not be above these values both to industry plants and thermal power station as regards air pollution control

Thermal power stations and other industries are also great sources of wastewater; which affects (the community of living organisms) of complex natural ecological system of water basins. These industries and thermal stations employ various schemes of water treatment before discharging the wastes into water bodies. But in most of the cases either the wastewater is directly disposed into water basin or is, not treated properly to insure the properties composition of water upto maximum permissible concentrations of harmful substances.

Cooling waters of thermal power stations carry an enormous amount of heat into water basins to have direct effect on the rate of chemical reactions and the rate of restoration o deficient oxygen. At higher temperatures, the rate of reproduction and growth of hydrobionts increases.

Wastewaters of water treatment plants contain various neutral salts, acids and alkalies which] change the Ph index. This wastewaters also carry unburned fuel, slime, coarse-disperse particles. Organic substances, iron and aluminum compounds, Mg (OH)2 and CaC03 which raise the BOD (biochemical oxygen demand) and affect the Ph index of the basin

This has serious consequences for the biocoenosis due to accumulation and rotting of organic substances (anaerobic respiration) and for the quality of water.

Petroleum products (various oils, sulphurous fuel oil, kerosene etc.) present in wastewaters of thermal power stations and practically any industrial enterprise can enter water basins in emulsified, colloidal or dissolved state.

These products can cause serious harm to water basins by forming films on water surface and thus in-habiting natural aeration. On the other hand, heavy products form bottom deposits, thus isolating the bottom flora and fauna from the remaining portion of the basin.

Besides, sulphurous fuel oils are detrimental for the spawning of valuable fish species even in slight concentrations (above -0.05-0.1 mg/kg). Their effects in water basins may be sensible for the long period.

In addition to the inorganic acids, organic compound and corrosion inhibitors used in washing procedures, wastewaters also contain in large amounts some harmful substances, for instance, copper, zinc, fluorine, hydrazine etc. Heavy concentration of these toxic substances may cause the death of hydrobionts, whereas lower concentrations change their metabolism, rate of growth, mutagenesis, and reproductive capacity. Zooplanktons are extremely sensitive to toxic substances and perish even at low concentrations of contaminants; this has the definite effect on the whole biocoenosis.

The ash formed on the combustion of solid fuels at thermal power stations is transported to ash dumps through dry and wet or hydraulic systems. In the latter system the ash is mixed with water to form pulp which is disposed to ash dumps.

The ash contains a large number of inorganic compounds and minor quantities of toxic compounds of geranium, vanadium, arsenic, mercury, beryllium and fluorine, which are of certain value for the national economy. Some carcinogenic substances can also form during fuel combustion and pass from ash to water.

The ash dumps area is considered to be unsuitable for agricultural utilization for 7.12 years. In addition, explosive discharges can inflict damage to forestry, particularly by inhibiting plant growth and impairing the quality of commercial timber.

2. The quantity of impurities discharged into water basins can be diminished by decreasing the discharge of impurities and by purifying waste waters. It also requires enormous quantities of clean water for diluting liquid wastes to maximum permissible concentration of harmful impurities. Dry methods of ash storage should be employed in which ash and slag are pelletized and then stored on worthless soils or used as building materials.

3. The influence of pollutants in relation to the turnover of substances in the nature can be discussed briefly. It should be recognized that the ejected products of human activity are not foreign for the surrounding nature, but participate in the turnover of the matter in the atmosphere, lithosphere and hydrosphere. For example, the atmosphere of the earth contains about 2000 billion tons of carbon. According to the World watch Institute fossil fuel combustion has contributed 150-190 billion tons from forest clearing. According to recent studies, deforestation adds 1-2.6 billion tons of carbon annually or between 20-50 percentages as much as the burning of fossil fuels.

At present the concentration of carbon dioxide in the atmosphere is 340 ppm as compared to 315 ppm in 1958. Scientists now predict that atmospheric level of C02 will nearly double to 650 ppm by the year 2050.

Carbon dioxide serves a function essential to the earth's habitability. Like one way filter, it lets energy from the sun pass through it, but traps the longer wavelength radiation emitted back from the earth's surface.

This phenomenon, dubbed "the greenhouse effect" helps regulate the planet's temperature. Scientists now estimate that rising level of other gases such as chlorofluorocarbons (CFC), methane, nitrous oxides, and ozone also together contribute as much to the green house effect as does C02 alone. When the level of such gases rises they trap more heat near the ground leading to a corresponding increase in temperature.

It is strongly believed that present atmospheric changes would increase the global temperature by 100°C during the next few decades.

This will help in melting glaciers and ice caps to raise sea level. Besides, as the earth warms the water in the oceans would also expand. US Environmental Protection Agency predicted a rise in sea level between 1.5 and 2.2 m by 2100. Various species of animals and plants may also disappear because of altered seasons due to rise in temperature. Increased temperature could also increase the respiration rate of trees. When respiration outpaces photosynthesis, trees would release more C02. If this continues for a long period trees would stop growing and ultimately die.

According to some scientists, higher levels of C02 would enhance the growth of them to remove more carbon from the atmosphere. But the climatic changes associate with the increase of C02 and fuel burning may counteract or reduce plant production.

With the above preamble the ecologically fragile environment and human health have create a sense of insecurity and uncertainty in the minds of masses.

The question arises whether th are indeed the necessary costs that humanity must pay in order to generate the much nee electricity and other industrial products or there could have been way of avoiding the environment degradation and how best could it now be possible to restore a healthy environmental and maintain a sound ecological balance in future.