THERMAL POLLUTION IN WATER

Abstract

Thermal pollution occurs as a natural process required by the Second Law of Thermodynamics for any thermodynamic cycle to operate. Water is often used as a cooling medium, which is heated and returned to the environment warmer than when it started. The problem is to reduce the impact this has on the environment and to reduce the total amount of heat rejected. The amount of head rejected to water bodies can be reduced by conservation, using alternated disposal methods such and cooling towers, and more efficient plants and machines. The impact of heat rejection can be reduced by limiting the volume exposed to elevated temperatures or limiting it to regions that do not cause environmental harm. The volume of water exposed to elevated temperatures can be reduced through the proper design of submerged discharge diffusers. Discharge at the surface produces a large surface area exposed to elevated temperatures but increases the rate of heat transfer to the atmosphere and keeps high temperatures away from some deeper dwelling organisms that might otherwise be harmed. The ability to predict regions of impact is important in determining if a particular discharge is acceptable or not. Several methods of predicting thermal plume dispersion are discussed including physical, empirical, integral, and numerical. Selected computer models using these methods available for public use are presented.