Causes of water polution

 The various causes of water pollution are:

1. Oxygen demanding wastes

    Municipal waste water and industrial effluents reduce the                    dissolved oxygen in water. When the amount of dissolved oxygen     reduces and the following effects are occurred:

    a) fishes and other aquatic life are threatened and in the extreme            cases killed.

    b) Undesirable odour, taste and colour make the water useless.

2. Pathogens

    They are disease producing organisms that grow and multiply            within the host. E.g. Bacteria, Fungi

3. Nutrients

    The nutrients like nitrogen, phosphorous, potassium etc. are                considered as pollutants when their concentration are large to            allow excess growth of aquatic plants and causes eutrophication        effect.

4. Salt

    Salt concentration in water reduces its acceptability for domestic,     industrial and agricultural purposes.

5. Heavy metals

    Heavy metals like mercury, cadmium, lead etc. are considered            as pollutants, as these metals adversely affect the human health.

6. Other pollutants

    The various other materials that causes water pollution are, plastic,     chemicals, marine oil, radio active wastes etc.