1. The contamination of water with unwanted and harmful substances is called water polution.
2. The biodegradable waste enters a water supply and thus pollutes water.
3. Chemical fertilisers from agriculture runoff due to rain and industrial waste pollute water.
4. Heat can be a source of pollution in water by decreasing the amount of dissolved oxygen.
5. Sediment consists of mineral or organic solid matter that is washed from land into water sources.
6. The industrial waste contains a large number of harmful chemicals like acids, alkali and metals such as arsenic, lead, mercury and cadmium leading to toxicity.
7. Hazardous substances like fluorine mixed in groundwater are causing pollution.
8. Thus nearly 70% of the surface water sources are polluted.
