SR-9 : Status of thermal pollution in water bodies

Abstract

Thermal pollution of water bodies is a very important and crucial phenomena and has drawn the attention of research workers for a long time, however in India, the studies on thermal pollution have been very few and in restricted manner. Before embarking upon the control or understanding of this phenomena, it was thought proper to come out with the status of thermal pollution at international level. The purpose of this report is to highlight the thermal pollution status, its effect on various physical, chemical and biological processes and to study the theory behind the phenomena.

The discharge of unutilized heat constitutes 70 percent of the total heat produced in a thermal plant whereas in nuclear stations it is slightly higher. The report opens with the definition of thermal pollution and its effect on various ecological sub-systems like micro-organisms, biotic life present in water and the overall effects on ecology and production of organic matter. Normally, the heated effluents are discharged at a temperature E, to 10oC higher than the temperature of intake waters. The heated water reduces the amount of dissolved oxygen contents and because of higher temperature organic matter decays faster. The other reasons for fish mortality could be due to synergism, because of other toxic agents present like chlorine, corrosion products and other preservatives. Fish deaths may also be because of super saturation from photosynthetic oxygen which causes gas bubble disease.

Various effects of heated discharges on water quality have been brought out which include stratification in impounded water, effect of differing density, effect on various water quality parameters (like DO, iron, manganese, temperature, waste assimilative capacity etc.), The benefitial effects of thermal discharges like greenhouses, aquaculture, agriculture etc. have also been brought out. It is also concluded that benefitial uses are not intended to suggest solution of thermal pollution problem but they should only be taken as means of improving the overall use energy resources and thereby enhancing the quality of life. The report also brings out the need for research in the area and ends with an exhaustive list of references on the topic.