Water pollution - thermal pollution

What is thermal pollution?

Increase in the normal temperatures of natural waters caused by intervention of human activities.

Give an example of a factor causing thermal pollution.

steam turbine power stations coolant water returning to bodies of water at a higher temperature.

Give the physiological effects of a rise in water temperature (6)

1. Aquatic life enzymes denatured

2. Increase in metabolic activity means heat loss so less energy available further up the food chain.

3. Different rate of egg development and hatching dates

4. Introduced species might be better adapted

5. Increase in toxicity of pollutants

6. Reduced resistance to disease

As temperature of water increases dissolved oxygen levels ____________.

Decrease (negative correlation)

Outline how power stations cause an increase in water temperature (4)

• Power stations take condenser water (used to cool steam) from rivers lakes or the sea

• Coolant water is returned at a higher temperature

• Large bodies of water will dilute the warm water with little effects on the environment

• Small bodies of water will have a harmful temperature rise.

What do cooling towers do?

Reduce coolant waste water temperature before it is returned back to the environment.

Explain how a cooling tower works (4)

1. Hot water is sprayed from the floor in the lower part of the tower (shower)

2. Air in the tower absorbs heat from the water and rises up the tower

3. Movement of air upwards draws cold air in which passes through the shower

4. Movement of air through the water cools the water and saturates it with oxygen

Why is the relationship between dissolved oxygen and temperature surprising?

• Higher temperatures usually means faster reaction times and increased dissolving but O2 dissolves better in colder temperatures.

• Hot solutions dissolved solids better