Pollution is an undesirable change in the physical, chemical or biological characteristics of an environment. The environment includes air, water and land.
Thermal pollution is the negative and positive impact of the heat contents of the environment under pollution considerations. Thermal pollution can be checked by considering the basic laws of thermodynamics and useful heat energy content properties.
Sources of thermal pollution
Thermal power station involves in larger scales combustion and consequential flue gases, these discharges are major causes of thermal pollution. The sources of thermal pollution can be summarized in the table below:
|Sources of heat||% heat|
|Fresh water discharges||6.5|
Effects of thermal pollution
- Physiological effect: this effect is predominantly in aquatic habitats and aesthetic values; this is due to increase in water temperature. This effect is not much recorded on human health.
- Effect on water quality: the temperature increase in water increases it’s properties such as viscosity, pressure, density surface tension and It has many effects to water bodies. Oxygen solubility in water has lots positive impact in aquatic lives. If the temperature is high, oxygen solubility is low with associated organic loads, increased respiration, thus, reducing oxygen dissolution and aquatic lives cannot survive at these conditions. Chemical effect of temperature rise results to high rate of reaction within a system. At equilibrium state, the constant is given as
Where E is the activation energy and R is rate of reaction.
Thermal pollution management system.
- Direct discharge: this is direct discharge of heat effluent into body of water. It can be subsurface or mixing jet method.
- Off stream cooling: this is when the heated effluent is cooled by inland generation of water near the site. This has no connection with rivers or streams. Due to cost analysis, each firm adopts methods cheaper to them such cooling pond, spray ponds and cooling tower.
pollution prevent and management
- Boiler blown down: in water treatment plant, all effluents are directed into a neutralizing pit and after considerable treating, it is discharged into drainage systems.
- CW system blown down/CW discharge.
- Water treatment plant discharge
- Ash pond outlet
Water supply, waste disposal and environmental engineering, by A.K Chatter Jee. Romesh chander khanna, 7th edition. P561-573
Environmental pollution and control in chemical process industries by S.C Bhatia, Romesh chander khanna, second edition P1026-1029