What are the major causes of water pollution? Explain.

Pathogens: Pathogens include bacteria and other microorganisms that enter water from domestic sewage and animal excreta.

Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis ,

which cause gastrointestinal diseases.

Organic wastes: Organic wastes when added to water, as these are biodegradable, bacteria decomposes organic matter and consume dissolved oxygen in water. When the concentration of dissolved oxygen of water is below 6 ppm, the growth of fish gets inhibited. Breakdown of the organic wastes by anaerobic bacteria produces chemicals that have a foul smell and are harmful to human health.

Chemical pollutants: Some inorganic chemicals as an industrial wastes dissolve in water like cadmium, mercury nickel etc. These metals are dangerous to humans and other animals. These metals can damage kidneys and central nervous system,lever etc. Petroleum products pollute many sources of water.

Thanks